We're going to give our attention to Helen Thackray. She's not Australian. She's a Ph.D. student from Bournemouth University in the UK and she finds humans and computers fascinating. She'll now attempt to explain some of the psychological group factors behind why hackers are always going to hack. Her theme is, hackers going to hack, but do they know why? Let's give her attention. Hello. Yeah, I'm very definitely English if the accent doesn't give it away for you. I just wanted to say when I found out in the schedule that I was following Chris, I was slightly nervous and then following that, good lord. But I just wanted to say that's an amazing project and I just want to give another round of applause for it because I think it's such a worthwhile thought. So onto a much lighter topic, hackers going to hack. Obviously you guys have some vague interest in this, otherwise you wouldn't be at DEF CON. I have to say this is slightly surreal for me because last year I was here, it was my first DEF CON, came to the social engineering village and it just blew me away. It was awesome and I really love the emphasis on education, helping people and coming here today and listening to Chris's talk again, it just emphasises what I do in part of my research, which is looking at the other side of hacking, not just the stereotypes, the black cats, the cyber criminals, but looking at what hackers can do that people don't realise what goes on behind the scenes. So yeah, my name is Helen Thackray, I'm from Bournemouth University, I've got my main supervisor John McElaney in the audience. If you speak to him, he's a lovely, softly spoken Scottish man, sometimes I don't always understand what he's saying, but we muddle through. So just briefly about me, because I'm pretty sure no one's heard of me. I'm a PhD student, I'm at the end of my second year of research, I've got funding for another year and I hope to finish in that time because otherwise it's going to get really expensive. I'm from a small, well I'm not from, but I study at a small town on the southern coast called Bournemouth, I drew a red arrow to help you. It's not particularly exciting, but the university makes up for it. If you don't like the C word cover your ears, because I'm in the field of cyber psychology, I didn't name it, it's not my fault. I also work with cyber security, so I'm in psychology and computing. Brief shout out to the Cyber Security Research Group, headed by Dr Shamal Fahley who helped with funding for this. Other than that, I've got no external connections or funding, it's the university funding this project. So just quickly, I realized I was quite flippant in my bio on the SEO, the social engineering website.  I do have a bit of an odd background. I'm very much the social science and humanities. My first degree was joined in Italian and politics. The Italian didn't stick so much, but the politics, I got really into political identity, social identity, why people choose the politics they do, what unites political parties and the whole personality of it. With political parties, there's a lot about the identity of the leader, how they present themselves. I thought that was really interesting. From that, I moved into contemporary identity and sociology and on a slightly different note, I looked at identity in cancer patients because you can exist, you have your whole self, you define yourself and then suddenly you get a diagnosis and then you get a diagnosis which completely changes your world and how do you deal with that? How do you deal with people treating you differently? That was really fascinating. I had some wonderful participants, but it led me to still enjoy social identity and what it is that people believe makes them them, how they choose, what they choose, what they do if they can't choose. How that came about to me studying the internet or people on the internet, I have always been a very curious child. My mother told me the story when I was about five coming back from school, kindergarten. There was a house, a door was open to a house on the street, we were walking down and I decided I wanted to go in it and my mother said you can't just go into people's houses and I said, but mum, I'm a very rude and nosy child, I'm going in and to five-year-old me, that was perfect logic. I've become less rude about it, but I'm still incredibly nosy, I want to know the answers to things. I also quite like watching people from a safe distance, which sociology, internet research, perfect. Also, I really like lurking on online forums. It's a terrible habit, I've been doing it since I was about 13. Weirdly, on an air gun forum was where I started and if anyone here is British you will know how peculiar that is. The UK has very strict gun laws, air rifles are allowed for hunting, pest control and target practice. As a 12-year-old vegetarian who loved her pet rabbit, I did not have a lot in common with the people on the air gun sites, but I had a neighbour who got into it, there were jokes going on, someone had stolen his team mascot and sending photos, sending it around the world, it was hilarious and I loved it, the jokes, so I started hanging out on this air gun forum, obviously not talking about air guns ever, but I loved getting to know the characters, the people, the in jokes, how they talked about representing themselves as a whole and without actually realising it, I was doing sort of ethnographic research on this community, I was sitting there reading about them, learning about them and to be honest, ever since I've been finding online communities to do the same things to you, I'm kind of creepy. So my talk today, basically I'm going to talk about a little bit about social psychology, social identity and then I'm going to look more at group processes, so everyone knows that you act in a certain way, depending on who you're around, like if you're with your mother or your father, maybe you swear less than you would with your friends, if you're with your partner you'll be a little bit more sensitive than you would with maybe your brother, it all depends, so basically social psychology boils down to all human behaviour is influenced by the presence of others, whether it's real or imagined, so for example standing in a lift by yourself, you might act completely as you want to, you could fart, pick your nose, whatever, then you remember that there's a security camera in the top corner and then you think, ah, someone will have seen that, you will modify your behaviour because you think someone will be able to watch me, and I think one thing that gets forgotten is that when it comes to infosec and cyber security is that this is all coming from behavioural actions, there is always a wider social context, it doesn't matter what end of the line you are, there are always people behind the computers and people are fallible and open to influence, so one thing that I do find interesting when I talk about my research is that the group processes that I'm going to go through, they're applicable to hackers and people in hacking communities, but they're also applicable to infosec practitioners, there are a lot of similarities, even if you have a very different viewpoint you've got a lot of the same skill sets, coding, finding access, having imaginative creative ways of thinking, finding and fixing a problem, not to mention that curiosity, so social identity, basically the world is chaotic and confusing, we make it a lot easier for ourselves by categorising everything, some things we put a lot of thought into, other things we just go with, well that looks similar to that, so we want the mental shortcuts, we don't want to use all our energy up, basically analysing and categorising every single thing we see, it's too difficult, the human brain just gets exhausted, so we put ourselves and others into groups, and these are called identity groups, so you might choose to identify yourself, for example there's a joke that I'm not Australian, I'm not quite sure where that jokes come from but I'm not Australian, I'm British, I'm also European, I'm also, yeah, sod Brexit, I'm also English, I'm a female, I'm quite posh sounding, I don't like sports, I think my hobbies are just lurking on the internet actually, which is a great hobby, I fully recommend it, but yes, we all have these different ways that we categorise, looking at me, you guys will have mentally categorise me somehow, and yes I do like tea, it's a wonderful drink, I don't understand why you guys haven't embraced it fully, I hear there was something about Boston and a party and it went wrong, good to know, thank you, so the identity groups that we put ourselves in, they're important to us, we get a sense of pride, a sense of self-esteem, if our group looks bad it reflects badly on us, the choices that we make, we ascribe to our group and we want people in our groups to have similarities to us, whether this is true or not, this is what we tell ourselves so our self-image is related to the reputation of the group, going back to Human Factors and InfoSec, one of the tropes that really bugs me is people like to say people are the weakest link, now I can't say that's actually wrong, because you know what everyone has a bad day, everyone makes a mistake, I remember last year when I was listening to Chris talk he told the story of how he actually fell for a phishing scam, an Amazon link because it came at the right time in the right place when he was stressed and busy and getting organized for DEF CON and he'd ordered things from Amazon, he was expecting emails from Amazon, he got an email from Amazon and he fell for it, it doesn't matter how well informed you are, how much you're expecting it, all it needs is the wrong moment, something to go wrong, you can be having a bad day, it doesn't mean that you're not smart to understand, so although people are the weakest link and some people really, really do need more education on it, we need to give ourselves more credit as a species, we've done quite a lot with technology, I mean even just coming to DEF CON, you can see people being so inventive and creative, basically I'm just being a little cheerleader for the human race, it's not all terrible, one thing that's emphasized in InfoSec and when thinking about human factors is the fact that there are very different ways of thinking, so there is the stereotype that computing likes to be more logical, calculated, analytical and you know, psychology is a bit sort of fluffy and it's all about emotions and talking about how you feel, I have to be honest I don't really want to know how any of you feel, but I think you can't have just one to make a good security, you need a team of both and as my slide shows I feel that Kirk and Spock are a good example of this, I know it's slightly flawed because Spock is half human, but go with it. So in terms of having the logic, you can have the most logical tool, you can create a perfect program, but as a comparison, what if people decided to make a hammer round instead of with a straight handle, because that way it's more efficient, you use more of the tree because you've got a hammer that a person can't use, that's not a useful tool, so although it may be less efficient in use of wood for the tree, a straight handle means more people can use it, more people are going to hit the nail on the head and that's what you want, so when you're making a good tool, it has to be understood that it's for human beings, and I think this is something that's coming to the front more and more in inflate sec discussions, I've been talking about this for years and things like that, and more and more they're driving home, you have to think about the people, it's the human element that needs to be worked on really. So this might be a little controversial, I fully understand that there are very different definitions and everyone has their own interpretations, but for the point of this talk and for simplicity, when I say hacker, I'm referring to a computer hacker to access a computer system without permission, without admission, they can find their way around, they can be creative. I put hacktivists there as well because I think it's a separate thing, political, social dissatisfaction means that they're using computers for a purpose related to that, they're not just doing it for the curiosity, they're not just doing it to get access, they have a different motive. Other thing, I definitely feel that a hacker is not the same as a cyber criminal, people that are doing their scams in order to get money, that's not a hacker. So when it comes to the hacker's social identity, it's quite a difficult thing to define because of course everyone has their own interpretation, there are so many different subcategories, black hat, white hat, gray hat, ethical skid, elite, there are some people that say that ethical hackers don't exist, there are some people that don't exist, it all gets very subjective. So hackers are an imagined community, this is a sociological term, it was coined by I want to say Benedict Anderson in Australia when he was talking about nationalism, because there were people all across Australia that were united in the idea that they were Australian, even if they were from different ethnic backgrounds, different political views, what it meant to be Australian, so there was no physical or geographical connection, it was a targeted community and it's created through the strong choice of interest and identity and if that doesn't fit to hacking, I don't know what does. And as you can see from being a part of this, hackers create groups, they give expertise, support, training, guidance, encouragement, so much to help people get further, which I think is amazing. So just briefly this is someone else's diagram, but I really like it, so I use it. He broke up into five basic categories, this does not cover all definitions, all possibilities, all motivations, but bear with me, breaking it up into these five basic categories, you can see the different reasons why people might get involved in hacking, those are in the brackets around the outside, the more sophisticated the level is, the closer to the edge of the circle and the type is by the dots, so for example if you hack for prestige, you're a coder, you're not doing it for any particular reason apart from to show that you are the best of the best, you're doing it to prove that you can. And it doesn't matter what the general public think, what the noobs think, you're doing it to show other people that you know who have the skills that you can do it to.  Revenge, there's crowd sources inside of threats, things like that. Profit, in my mind that's the most boring category, because it tends to just be the criminals, although I feel there should be some sort of sub-category for people who are in the business of information security, but there you go. And then ideology, you've got the hacktivist cyber warriors, people fighting for a cause. So, back to the social psychology of individuals and groups. I just thought this quote was quite apt from Men in Black, Agent K saying to Jay, a person is smart. People are dumb, panicky, dangerous animals, and you know it. I don't think that's the entire truth, but I think it can be agreed that people behave very differently by themselves versus in a big group. When it comes to the panic, I'm not going to be discussing mass panic behavior changes in that, because that's a fairly different thing. But you bring people together in a group, it changes things. So, for example, I'm going to say you guys a group A, you guys a group B. I'm going to come back to that. So, one of the things, more common things that you might have heard of when it comes to group changes is group think from the 1970s. And basically, it's a psychological need to have consensus. It doesn't matter if you have to suppress disagreement, it doesn't matter if you have to ignore individuals' opinions. You don't look at all the information, but you want consensus. You want agreement. Symptoms of it are the group thinks that they're invulnerable, regardless of the reality. They collectively rationalize their decisions. Even if there is evidence to the contrary, they, you know, disregard that. They have stereotyped views of different groups, rather than, you know, looking at what they're actually made up of. There is the group pressure to conform and people tend to self-censorship. So even if they don't agree, they will suppress their own views. No one else has to say anything to you them, but to stay in the group, they will stay quiet. Group thinks been found to be more common when the groups are tightly bonded, more cohesive, especially in a high-pressure situation. If there's a lot of pressure on, they need a decision quickly. Group think emerges. However, group think also reduces the possibility of success. So they come to a conclusion it's more likely to be wrong. And the pressure for agreement makes people think more rationally, it makes them vulnerable. It's just generally not a good thing. Informational influence. So this is the desire to be correct. No one wants to be wrong. No one wants to stand up in front of a crowd like this and say the wrong thing. This is why I have names and dates in there. So I can say it wasn't me that said this. This is the study. The sources are important. We instinctively look to other people to see how we should behave, what is acceptable, what is the norm. So, for example, if you go to the UK and you see people queuing, you queue properly. Not that that's a pet peeve or anything. You get the information and news from the group.  Therefore, the group view is the correct view. You don't want to be excluded from the group. You don't want to be the old one out. You don't want to be the difficult one. You want to be accepted as part of a group. Therefore, you behave as they would want you to. Similarly, you've got the normative influence. Pressure conform to the norms. So, for example, online, you have this by obeying the laws of a forum. I don't know if anyone's actually set down and read them, but I go on a lot of hacking forums. I read all the rules. They're very similar. All of them saying, don't do this. Don't do this. It's illegal. No money. No anything else. And then everyone ignores it, obviously. But they say it. That's not how they behave, though.  So even if an individual doesn't agree with the norm of the group, they still won't speak up because they want to stay in the group. It's also been found that if people express an opinion and other people say, yeah, no, I agree, then that will encourage the person to give a stronger opinion, a more polarized opinion. And there are links to group think and the conflict between groups. Also, a very important factor as to whether or not people conform to the norm, which rhymes, is whether or not they're being watched by a larger group. You behave better if you think there are security cameras around. This is why people have fake cameras. Yeah. So it's interesting how we can ascribe certain behaviors to other people because that's who they are. But ourselves, no, we're different. We're better. We know our motives. We judge others by their actions, ourselves by our intentions. And I love this cartoon, XKCD, for those that don't know but you probably do. Because, yeah, everyone might be thinking exactly the same thing as you. Why is no one saying anything? But you don't. Why don't you? So you're in this group. You want to stay in this group. You belong to this group. Because you belong to the group, you want to feel good about being in this group. So group A, you guys are some snappy dresses. You're all looking good there. That's very nice. So you find good things about the group. But then you have to also discriminate and find negative things about the other group. No offence, guys. I love the bunny ears. That becomes a them versus us. Just social categorization. So by putting you in two groups and saying slightly different things, you might feel more like a group than you would if I'd just left you all alone and not said anything about it. But just by putting people into a group, they assume the group identity. If I'd said all blue-eyed people go to the left, all brown-eyed people go to the right, they would be a bigger group. They would be the majority. The minority might feel that it's not so fair. Everyone in the brown-eyed group could have a chair, but all the blue-eyes have to stand. That's not fair. Why would you do that? You can create tensions and rivalry and competitiveness that doesn't need to be there just by arbitrarily grouping and categorizing people. Stereotyping also exaggerates the difference. It can also make you think you're more in common with another group than you actually have. So groups, as with giving a stronger opinion because you're in a group, they become more polarized. So you can go to more of an extreme. I think politics is a great example of this. But I'm not going to go into politics. So when you're in a group, especially online, how do you know if you're in a group or not? There's no list where you sign up your name, there's no... You can actually register for forums and you can be a group member in that sense. But for example, 4chan, triforcing, they've come up with a way to signal whether you are in or out. And I quite like this as an example because I think it's quite clever. So the triforce, I'm sure most people are familiar with, it's from a video game and it's basically placing those three little red triangles correctly. If you copy and paste it, it will come out incorrectly. So what they like to do is someone starts the thread with the triforce, someone copies and pastes, it looks correct until they hit Submit, then it comes out wonky. Everyone can see that they don't know how to triforce. It's a way of outing yourself. Not that it particularly matters on 4chan because everyone's called anonymous. But in this picture, in this example, someone had said, oh, here's one that you can copy and paste. Another person did the correct triforcing to make it seem believable. Then someone tried to copy and paste, got it wrong, everyone laughed. So there's subtle ways that you show whether you're in the group or not. People that are wearing Def Con t-shirts from previous years, they're saying I've been coming to here for years. People with loads of badges around their neck, I'm involved in all these different villages and I've been to all these different talks, I've done these different challenges. There's ways that you are telling people you are part of the group. When it comes to conflict within groups, why does it happen? You've got a big happy group A, why would you guys all fall out? You could disagree about what's acceptable. You could say, sitting there playing on your phone, that's not what group A does. You need to go to group B if you want to do that. I'm not sure I'm not sure you should start doing that. This is the conflict within groups. We've done that against groups. People can have different motivations, different goals when it came to 4chan merging into becoming anonymous because the hacktivist group anonymous it started on 4chan, started out people trolling and pranking and generally having a good time. Some people were like, hey, let's use this for a cause. Let's do this to wind up people that we don't like, like Scientology, Church of Scientology. It got to a point where the original prankers were like I don't want to be doing this for a good cause. I just wanted to be a nuisance. They had to split between the people that wanted to prank and the people that wanted to have a good cause. When a group gets too big and too diverse it's natural that it falls apart to a degree. There's only so many resources around and cooperation can turn into competition. It's also especially in the hacking situation it's interesting how people divide along what isn't acceptable in order to achieve the goals. So it's black hat hackers versus white hat hackers how real it is can be hard to tell from my point of view. One of the other things that a group process that affects people is impression management. Groups want to control how they're seen. They have a brand. They have a reputation and they have to maintain it. They have to control the information that goes out and the perception that other people have. The use of this in online media is really interesting. Twitter's great for it. Some people are very careful about what they tweet. It has to be approved. Others, Donald Trump, not so careful. Not so... I know, sorry I said I wouldn't do politics but it's hilarious. So even when you're just coming to DEFCON presenting yourself you are presenting yourself. There is no two ways about it. Also when you come to these groups, trust. It's an interesting one in hacking communities. Oh, I've got so much fun with this. Trust requires the individual to relinquish control. You put yourself in the hands of another somehow. So for example, if you got the plane here you put yourself in the trust of the pilot. You trusted that the airline had checked that he was qualified. He'd actually done the test. He could actually fly. Everyone made it as we know, so that's looking good. There is also the expectation that others will reciprocate. So for example, getting on the airplane they expect that you will behave as a good airplane passenger and not get really drunk and harass flight attendants. Online, you don't get the visual cues of trust. You can't see how a person is standing, how they're talking, if they're doing shifty eye movements.  It might be a photo, it might be text but it can be manipulated so much more easily. And it's really interesting looking at what does and doesn't encourage trust online. One of the things is reciprocation of information. So if you're sat there talking to a stranger on a chat and you're telling them all about your life and they're just responding like, yep, okay, alright. At some point you're going to think well either they're not interested or this is just a really weird interaction. If they start telling you things about their life you feel a lot closer to them. You feel that there's more of a bond, there's more trust. And this is how people can be manipulated so easily. I think in the UK at least there's been a big rise in dating scams because people are looking for these sort of connections for friendships and they trust. One of the sad things about social engineering is that I mean a lot of people I really like here that they emphasise that it's not the person's fault. It's that they're not taught or prepared well enough but there is an element of taking advantage of someone's naivety and good nature and their trust and it's quite sad. But going back to hacking, group membership is a strong predictor of trust behaviour. If you belong to the same group as someone else you are more likely to trust them. So for example, walking around Las Vegas if you see people with their DEF CON badge you might be more inclined to start a conversation with them say hey you're at DEF CON, watch your background, what do you do? Is DEF CON, some people will be a little bit more wary of what they say but there's still the element of we are in this same group this group within the wider group of all tourists and workers in Las Vegas. So the fact that you are all here at DEF CON means that you already have something here in common. What's been interesting in the research I've been doing and interviews I've been doing when I ask about trust everyone immediately says don't trust on the internet no trust, don't trust anyone there could be a dog but how far does that actually go? How far can you actually get interacting with other people if you have literally zero trust? When I've pointed this out to them and given examples it's been quite interesting how they found that very hard to reconcile with their idea of I don't trust anyone. There was one person I was talking to who had created their own forum and it was towards the darker side and he was quite openly talking with me and I said so do you run it all yourself like 24 hours a day he said no no I have admin but you said you don't trust anyone he was like no I don't trust them but do you check what they're doing all the time and he said no no okay yeah I trust them to do the admin so where does the line of trust stop you trust them with your website what you have created you trust that they will uphold the rules and the norms so what don't you trust them with and if it comes down to you know your personal identity well you wouldn't trust most people on the internet with that so it's interesting trust is tricky so how is this relevant to why hackers are going to hack basically I just wondered how many of you were really aware of all the different things that might be influencing you without you actually thinking about it so for example what you've chosen to wear today if you're wearing a deaf con t-shirt like I said before maybe you want to tell others previously you know what you're doing if you're wearing a company t-shirt you're saying yep I'm a part of this company I support what they do if you're wearing I don't know a sports brand then maybe you're saying you're sporty I'm not sure why did you choose the talks that you went to if you've come to this talk then hopefully you've got some vague interest in social engineering or social psychology human factors if you've gone to one of the really technical ones then you're saying that you're technical because your friends wanted to go or the people that you're with or you just didn't want to go sit in a room by yourself you wanted to be with other people so you let them influence your decision have you had any disagreements with the people that you came here with if you didn't come here with anyone you have so much freedom it's wonderful if you did there's peer pressure what if you don't want to go out and party what if you want to go sleep because let's be honest it's tiring I disagree with that which also there's disagreement so there's all these different things what keeps you coming back to DEF CON in the different days is it's that you want to be a part of this social identity is it the curiosity you want to find out you want to learn is it the sense of community that you want to be a part of there are all these different group factors that keep people coming back to hacking and that's it's one of the things that my research really aims to get into so again how does this affect you well when it comes to trust would you trust the person next to you not for example with your home address or your mother's maiden name which I've never understood because my surname is my mother's maiden name but would you give them your wallet and go to the toilet the person who said yes so you sat next to someone you know okay well that's married to trusting your wallet with your wife that's anyway before I get before I start a domestic so when you're talking to other people at DEF CON how much do you tell them about yourself about where you're from about what you're doing I have to say I'm always a little bit wary telling people about what I do because mostly because I have to say yeah I'm here to study you I get a mixed response to that but how you present yourself is also important so group influence is it good is it bad I'm going to give a very psychological answer it depends it can be it depends cybersecurity they'd say it depends on what the group is doing if they're encouraging you to do naughty bad things then they are bad but more importantly regardless of whether you're doing good or bad can you recognize when you're being influenced do you actually think critically when your friends are trying to persuade you to do something that you don't want to do do you stop and think maybe this isn't a great idea maybe I should just go and do what I want to do and I think this is especially important in the whole error of fake news and social media tunnel vision don't dismiss information from other groups in fact sometimes it's really useful to look at information from other groups to see where they're coming from you might not agree but you get a better overall perspective so little bit of self-promotion briefly my research so as I said I'm in the second year of a three-year studentship at Bournemouth University I have no qualifications in psychology or computing but I'm actually doing alright at this I'm so glad this is being recorded so my research is on the psychological influence of group processes online all the things I've been talking about I want to see how far they go from offline to online because that's something that we really are not understanding at the moment how psychology changes when people go online how the human behavior changes there's things like online disinhibition people behave differently because they think they're protected by anonymity because they're behind a computer screen you can become a keyboard warrior or in the instance of that famous YouTube comment Navy Seal Commando the other thing is what is the hacker identity there is a lot of different opinion misconceptions people do think a hacker is a cyber criminal it's not the case, some people can hack without actually breaking the law I don't know if they enjoy it but they do you don't have to accept the negative stereotypes as fact the hooded figure crouching over a keyboard you know what, lots of people wear hoodies they're damned comfortable so what's the point of my research I want to inform and educate not just the general public because they do need it but also people that are involved in these communities people that might be vulnerable to influence people that come looking for a sense of belonging and then are at risk of manipulation they had it in Anonymous where there were people that got prosecuted for taking part in the DDoS attacks they later said they were told to download the software, click the button they didn't really understand what they were doing I mean partly that's their fault because don't trust people in the internet but there is also an element of they were being manipulated they wanted to be a part of a cause they wanted to do something worthwhile they wanted to help and people took advantage of this to use them basically as cannon fodder I also think we're raising a generation of coding there's so much emphasis on computer science learning, all of these things we also need to teach the younger generation responsibility for online behavior and your online actions it's not disconnected from the real world there are consequences you can end up in jail for something you tweet I think it's also really important to emphasize human factors in cyber security it's not just about the programs it's about people I think there's a definite need for informing policy and legislation possibly this is me just being cynical but I don't like the idea that governments and corporations would be in charge of the internet because as we all know he who controls the internet controls the universe and I think that research such as this it's you can go with evidence and say you know you think that all the bad people are doing this here's what they're actually doing they're creating things to help locate and find people that are trafficking children they're doing good things it's the biggest evil just because you don't understand it the last latest thing to really annoy me was Theresa May's words about encryption and how she wanted to backdoor and I think you just don't understand you know there is no backdoor that only lets in the good guys and finally I think it's really important for cyber sociological knowledge to be expanded it's new it's interesting I'm sorry but you guys are a really fascinating community to do it with so how does the internet change the behaviour I've already been able to write a paper on how to go about this sort of research how to expand it it's bizarre but that this is such a new area how am I doing my research well I work on forums a lot I don't know if I've mentioned that I observe I come to conferences like this I talk I watch I make notes always anonymous never write down names dates or anything like that I do online surveys I ask people to fill in things and I'm currently doing interviews so and when I'm doing all these things what I'm looking for is examples of trust decision making risk taking looking for similarities differences patterns in behaviour one thing that I really feel that is important in my research is the privacy and anonymity of hackers I want to know how far they are aware of the group processes I'm very aware of the possibility of low participation and being trolled in one of my early surveys I had someone respond that they identified as a dolphin and when asked why they use the internet it was to hide their flippers someone else also gave their sexual identity as a jar of mayonnaise I could be behind with the times I don't know there's also the potential risk of backlash I'm standing up here with these opinions people might not like it they could decide to prank me dox me whatever so far it hasn't happened abuse on the forums yes there has been some of that I have been referred to with various four letter words and some people have said quite mean things about my mum but she has assured me that they are not true the data I'm collecting has been through online surveys I've got really good responses from them I've asked questions about it they want to know about the ethics why I'm doing the research what it's going to be used for some people obviously very cynical that my research can be used to infiltrate groups by agencies and law enforcement and things like that the trouble with research is once it's out there it's available to everyone it's not my intention I don't like the surveillance state but it's a risk just briefly I'm going to share some of my initial results that I've got so far I did an online survey across 30 websites and subreddits I had over 150 responses which I thought was pretty good considering that not everyone wants to tell a researcher everything they do online four forums banned me entirely but they were forums related to cracking so I get the feeling that they didn't really care about anything that I might want to say surprisingly the majority were male 6% female 2% transgender the age range was 16 to 63 which I thought was a pretty good spread one thing that I think is often overlooked is that there is an older generation of hackers hacking and computers have been around for 30, 40 years some people don't stop some people just get older, have families, children legitimate jobs they can still enjoy hacking so the stereotype of teenagers messing around in their room is pretty true but I think it's missing the point the average age of all the people that took my survey was 30 so I don't know what that tells you millennials so hopefully you can see this alright one of the questions that I asked was do you consider yourself a hacker bearing in mind every single forum or subreddit I posted this on I had found through searching for hacking, cracking, coding white hat, black hat, skids all these different things, as many different variables as I could think of everything was related in some way to hacking over 150 did the survey 52% said that they would say that they were a hacker just over half I found that really interesting on these websites specifically for hacking most of the people just under half the people didn't think that they were a hacker so of the people that said yes 52% I asked them to categorise themselves further so grey hat, white hat cyberpunk, hacktivist, other I disagree black hat, script kitty, elite and cracker to be honest I thought I disagree would have more responses just to say they could select more than one option so please don't try and make sense of the percentages it's the percentages of that participants not of so obviously a lot of people categorise themselves as a grey hat as well as other things that's kind of fascinating for me because that's such an ill-defined thing black hat, yes, you can say black you do nefarious things dark, white hat, you have to be ethical pure, everything else grey it could be anywhere in between you could be bang in the middle you could be just a shade lighter you could be categorising themselves as so I also did a couple of questions on privacy anonymity, shockingly people in hacking communities think that privacy is important and it should be protected and they take precautions with it the same with anonymity anonymity is an important feature of the internet it should be protected and they take steps to make sure that they are anonymous online then it got a bit more interesting online security should take priority over personal privacy there was a mixed feeling about this and then I asked if people try and find flaws and weaknesses and a lot of people said yes now this next slide, when I presented this to the computing side they had more of a surprised reaction so I don't know how well you can see but the blue lines are that the weaknesses and flaws should be exposed the green lines are that they should be exploited bearing in mind the idea that all hackers are bad and evil and do bad things it's very surprising that actually a lot of them, the majority say that they should be exposed but exploited there's not a strong agreement there it's obviously not as black and white as people would like to believe which ties in nicely with the grey hats category so what am I doing next I'm conducting interviews with volunteers if anyone would like to volunteer then that would be super if you think I've said something really ridiculous tell me but tell me why don't just send me messages saying that you think I'm an idiot that's rude and I've been taught not to be rude my next surveys are going to focus more on trust, decision making how people work in groups but tell me I can only do better research which will go out to the general public if people help me and of course I'm always going to lurk more so my conclusion for my research so far hackers are actually interested in informed groups people want to share their thoughts people want to improve the internet and security I worry about where the internet is going I like that there are people that take an active interest in making sure it goes in a fair and equal direction being a hacker being aware of security, being aware of the risks it doesn't make you infallible to the influence being aware of the group processes you can still be vulnerable I think it's important to highlight the significance of social psychology especially in online communities and social engineering it's right there and just to bear in mind that you can have different identities but ultimately we're all in the same social space thank you very much for listening four minutes left does anyone have any questions yes? naughty you just said one more time you can't then say another naughty so did everyone hear that what are the differences between groups are there any interesting results so far when people have categorized themselves they tend to be dismissive of the other groups which fits with the traditional I like my group I don't like anyone that's not in my group the easiest obvious most obvious one of that is black hats versus white hats it's interesting actually there's quite a lot of derision towards script kiddies in forums that's often used in a derogative term but people still identify themselves as script kiddies which is kind of interesting I mean it's not supposed to be something that you aspire to but they're still saying yep that's me so I'm sure there's a lot more to come okay yeah at what point are you comparing contrast how the behaviors are going different there's the aim to mostly I'm using social psychological theory to see if the behaviors match in terms of comparing it's quite difficult to think of scenarios where it would be I mean I've had people there's a forensic psychologist at my university who started talking to me about criminology and how you compare hacking communities and crime gangs and I was like that's not that's not quite what we're doing here so I think there's definitely research area there but you've got to be careful with it because you could go down the wrong track do you cross check your data that you got from surveys with non-survey based data and be less objective the trouble is there isn't a whole lot of data about hackers you guys are kind of secretive I am I am trying and there are various other studies out there there was a paper from a few years back where people had done data collection here at DEF CON it's a terrible paper I'm not going to say what it is actually because I'm still being recorded but no I disagree with their methodology I disagree with their conclusions I think the whole thing was very poorly thought through and that's the trouble even when you can find other data is that it might not actually have been as well done as it could have been one more question but I ask about offline extensions and I treat it as such so I ask how they got into it whether they were introduced by an offline connection or if they made the offline connections through the online so I try and find it out that way I think that's it if anyone has any other questions feel free to come find me all my contact details are up there and I love getting messages thank you


Hi, welcome to nursing school explain in this video on epidural and subdural hematoma. While they are both similar and caused by head injuries, they might be different and it's very important to know what distinguishes them. But first of all, let's review the anatomy here. So we have the head that's protected by our skull and inside there are several layers that are designed to protect the brain. Now the first layer underneath in blue is the duramatter and then underneath that we have the subarachnoid membrane and then below that we have the pia matter which just lines the immediate surface of the brain. So now depending on where the bleeding occurs is an epidural above the duramatter or a subdural below the duramatter hematoma, a bleeding. Now I've also drawn out here a subarachnoid hemorrhage which is below that subarachnoid membrane or an intracranial hemorrhage which is within the brain. All four of those really cause increase in intracranial pressure but depending on the layer and what causes it or what type of bleeding causes it, the patient might have different symptoms. So keep in mind that any kind of trauma to the head can cause bleeding inside the head so that most of them occur due to motor vehicle crashes or falls and specifically older patients have an increased risk because their brain atrophies over time so there's a lot more room for the brain to be jarred around if there is a fall and therefore there are increased risk because of falls. And so the other drawing that I have here is that we need to keep in mind that in our head in our cranial cavity there are three compartments which first we have the brain that consists about 78 percent of the intracranial contents. We have blood all the blood vessels that supply the brain and then we have cerebral spinal fluid which is about 10 percent and our bodies are designed in such a way that the skull protects the head from outside injury which is a nice design but now if one of those compartments brain blood or CSF takes up too much space there's nowhere else for the other compartments to go because the skull is a closed cavity which is why in children when they have increased intracranial pressure and their sutures, their fontanelles have not fused yet you might see bulging fontanelles so now the brain has somewhere to move but in adults or once the fontanelles have closed the brain really has nowhere to go if there is a bleed let's say so now there is a big hematoma in there the brain might shift to one side or the other which then leads to increased intracranial pressure and I'll have a separate video about intracranial pressure and how to manage that so now let's focus on subdural and epidural hematoma so over here an epidural hematoma occurs like we said above the dura mater in the brain it is a neurologic emergency because it is a blood vessel tear and it usually is an artery that ruptures and recall that arteries are much higher pressure than veins and so the bleeding occurs much faster than it would and so the blood the bleeding rapidly expands and the tale tale signs and symptoms is that there is some sort of a traumatic injury on the scene if somebody observed it there is a positive loss of consciousness so the patient loses their consciousness and then they have a brief lucid period where they appear to be completely abnormal and then all of a sudden their level of consciousness decreases again so that is kind of the tale tale signed because of this arterial bleeding and as with any kind of intracranial pathology there might be a headache there might be nausea and vomiting as the meninges get irritated treatment for an epidural hematoma it's an arterial bleed so we need to stop the bleeding so it involves rapid surgical intervention to evacuate the hematoma and prevent herniation and herniation basically happens so when now we have a bleed like over here we have this epidural hematoma on the left side if we had that here that would mean that the brain moves over or gets pushed over towards the other side because that blood the bleeding now is taking up too much space and when there's the bleeding extends then the brain can only move so far and then eventually it will get pushed down on the brain stem and then there will be basically dire consequences as the main the basic functions that the brain stem controls start to cease not working anymore and i'll go over that in the intracranial pressure video so rapid surgical intervention is needed to evacuate that hematoma that usually involves a kerinolomy so basically drilling a hole inside the skull and draining that blood out and then manage the intracranial pressure and like i said you can wash it in a different video now in contrast the subdural hematoma is an injury to the brain tissue and the blood vessels and those are usually venous you know in origin that means that the bleeding usually occurs a little bit slower that doesn't mean that subdural hematomas are not as dangerous as epidural hematomas but because the bleeding occurs a little bit slower we have a little bit more time to treat the patient and detect this when an epidural hematoma just is an arterial bleed that rapidly expands really we only have a maybe an hour or two to get this patient to the OR to get this epidural hematoma evacuated otherwise they are basically going to be brain dead and for subdural hematoma we have to distinguish between acute subacute and chronic and that basically just means the when the hematoma occurs and the symptoms that you'll see so acute is between 24 to 48 hours after injury subacute is in between two to 14 days and chronic can be weeks or months after what might only seem to be a minor head injury so this might be an older person getting inside the car bump in the head on the car door they are fine initially but then maybe weeks down the road they start to develop decreased level of consciousness or some very strange symptoms while it turns out that they had a very small blood vessel that ruptured that just slowly leaked inside their brain or inside that subdural space and now they're exhibiting signs and symptoms and like I stated before older adults and also patients with alcoholism are an increased risk for subdural hematomers specifically the chronic ones because their brain tends to be atrophied so again when the brain gets jarred inside the skull there's a lot more room for it to move around and a lot more chance for these blood vessels to rupture signs and symptoms for subdural hematoma include signs and symptoms of intracranial pressure decreased level of consciousness and again headache nausea and or vomiting now treatment because it depends on how significant and how big the bleeding is might range from what for waiting to evacuation of the hematoma like we saw the epidural hematoma and a lot of times these are patients that get admitted to the hospital with a small subdural hematoma they might not have any neurological signs and so they get admitted and they get repeated CAT scans maybe initially every four hours and maybe after the fact every day to see is it expanding is it shrinking is it staying the same can we just watch this and observe the patient very closely or do we have to eventually treat it and evacuate it and again here we want to manage the increased ICP now for nursing care in general for patients with any of these epidural or subdural hematomas we want to maintain cerebral oxygenation and perfusion and that really depends on the cerebral perfusion pressure and please watch my separate video that goes into the details of how to obtain that and then we want to do frequent neural checks and Glasgow coma scale as well as the entire cranial nerve and peripheral neurovascular assessments to see is the patient getting better worse or staying the same and then frequent monitoring of vital signs and the temperature is especially important to monitor if there is an injury to the hypothalamus because again that is the center of the brain that regulates the temperature and if there's an injury it might not be working appropriately and the patient might have very spiking or low body temperatures that you can that you could maybe mistaken for other things like infection so we need to very closely monitor the vital signs and then we need to check for CSF cerebral spinal fluid, otorrhea and rhinorrhea and rhea always means just fluid coming and otto either from the ears or rhino from the nose and so that means that CSF could be leaking out of the patient's nose or ears and that would be if there's an interruption to the skull or to the to the meninges that that protect the brain because the CSF usually shouldn't be coming out of the nose and ears and the way we do that is the patient all of a sudden you know has nasal drainage or ear drainage then you could collect that with a piece of gauze and then there will be the the what's called the halo sign so if you put and a lot of times it won't be just clear fluid it will be mixed with blood so you put that on a piece of gauze and then in the middle you can see that there is blood and then around it the CSF will separate and will make a halo around that piece around that drop of blood or that area of blood that's in the middle and that's a very of course informal test so if we're really concerned about that we need to collect some of that fluid and send it off to the lab for analysis to see if it's really a cerebral spinal fluid and then of course if there is maybe an infection associated with it because now if we have this interruption of the meninges and all these layers that protect the brain that are intended to protect the brain and now cerebral spinal fluid is leaking out foreign bodies bacteria viruses can get in there and then causing um meningitis so that would be a major concern here so if we witness the CSF otorrhea or rhinorrhea we definitely cannot pack the nose or ears we don't want to pack anything in there and then basically just pushing that CSF back because it might increase our intracranial pressure we definitely don't want to place an NG tube in there if there is drainage from the nose we will be very very careful with suction or we don't want to perform any kind of nasal suctioning and again because there's this risk for meningitis so hopefully this video has helped you determine between epidural arterial and subdural more venous type bleeding inside the brain that's caused by any kind of head injuries please also watch the video on increased intracranial pressure as well as intracranial pressure and cerebral perfusion pressure and how those two relate to one another to maintain the patient's neurologic status please give me a thumbs up if you've enjoyed this video subscribe to my channel follow me on instagram to stay up to date on the latest releases thanks for watching


Hello and welcome to this presentation on the STM32 Timers. It will cover their main features, which are useful for handling any timing-related events, generating waveforms, and measuring the timing characteristics of input signals. The STM32 embeds multiple timers, providing timing resources for software or hardware tasks. The software tasks mainly consist of providing time bases, time-out event generation, and time triggers. The hardware tasks are related to IOs. The timers can generate waveforms on their outputs, measure incoming signal parameters, and react to external events on their inputs. The STM32 timers are very versatile and provide multiple operating modes to offload the CPU from repetitive and time-critical tasks, while minimizing interface circuitry needs. All STM32 timers, with the sole exception of the low-power timer, are based on the same scalable architecture. Once the timer-operating principles are known, they are valid for any of the timers. This architecture includes interconnection features and allows several timers to be combined into larger configurations. Lastly, some of the timers feature specific functions for electrical motor control and digital power conversion, such as lighting or digital switch mode power supplies. Here are the key features of the STM32 timers. All timers are based on the same architecture and are available in several derivatives listed later in this presentation. The timers mainly differ in the number of inputs and outputs they have, from a pure time-base without any IOs to an advanced control version with 9 IOs. Most of the timers feature 16-bit counters, some have 32-bit counters. Some features may not be present on the smallest timer derivatives, for example, DMA, synchronization, and up-and-down counting modes. Most of the timers can be linked and synchronized to build larger time-base timers, have a higher number of synchronous waveforms, or handle complex timing and waveforms. Within a timer, each and every channel can be configured independently as an input, typically for capture or as an output, typically for a PWM. The timers can serve as a trigger for other peripherals, for instance, to start ADC conversions or to monitor the internal clocks thanks to the interconnect matrix. This slide provides the block diagram of the medium-featured TIM-15 timer. The timer kernel consists of a 16-bit up-counter coupled with an auto-reload register to perform the counting period and a repetition counter to adjust the counter-rollover interrupt rate. The two timer channels are controlled by two capture-compare registers. The counter is fed by the clock and trigger control, also responsible for the timer chaining. Shown on the left are the input stage and the input conditioning circuitry, while on the right we have the output stage. It includes dead-time insertion for providing complementary PWM outputs suitable for half-bridge power stages. Note that TIM-XCH1 and TIM-XCH2 appear on both sides to indicate that they are both input and output capable. Finally, a TIM-XBKIN input can be used for a PWM emergency shutdown. The timer features multiple clocking options. The clock and trigger control, also responsible for the timer chaining, handles the clock for the counter. The default clock comes from the reset and clock controller, linked to one of the APB clock domains. The various timers are shared on the two APB domains to implement low-power schemes, typically one high-speed APB and one low-speed APB to limit the current drawn by the peripherals, including the timers. External timer clocking allows counting of external events, or to have a counting period externally adjusted. The clock source can be provided by other on-chip timers, using one of the four internal trigger inputs, ITR1 through ITR4. The input pins 1 and 2 can also serve as external clocks, with the option of including digital filters to remove spurious events. The external trigger input, ETR, can be configured as an external clock with a digital filter, programmable edge sensitivity, and a first basic pre-scaler stage to reduce the frequency of incoming signals, if needed. Lastly, the quadrature signals from an encoder can be processed to provide a clock and a counting direction, as described later in this presentation. This slide explains how to adjust the timer counting period. Each timer embeds a linear clock pre-scaler, which allows you to divide the clock by any integer between 1 and 65,536. This allows the counting pace to be precisely adjusted. For instance, a division by 80 will yield a precise 1 MHz counting rate when the APB clock is 80 MHz. The auto-reload register defines the counting period. In down counting mode, the counter is automatically reloaded with the period value when it underflows. In up counting mode, the counter rolls over and is reset when it exceeds the auto-reload value. An update event is issued when the counter underflows or overflows and a new period starts. It triggers an interrupt or DMA request that is used for adjusting time parameters synchronously with its period, which is useful for real-time control. This update event triggers the transfer from preload to active registers for multiple parameters, and in particular for the clock pre-scaler auto-reload value compare registers and PWM mode. An 8-bit programmable repetition counter allows you to decouple the interrupt issuing rate from the counting period, and have, for instance, one interrupt every single, second, third, and up to 256th PWM periods. This is particularly useful when dealing with high PWM frequencies. Some of the STM32 timers feature up and down counting modes. The advanced control timers, 1 and 8, and the general-purpose timers, 2, 3, 4, and 5. The counting direction can be programmed by software or automatically managed by the timer in center-aligned PWM mode. In this mode, the counting direction changes automatically on counter overflow and underflow. For a given PWM switching frequency, this mode reduces the acoustic noise by doubling the effective current ripple frequency, thus providing the optimum trade-off between the power stage's switching losses and noise. The counting direction can also be automatically handled when the timer is in encoder mode. Quadrature encoders are typically used for high-accuracy rotor position sensing in electrical motors or for digital potentiometers. From the two outputs of a quadrature encoder sensor, also called an incremental encoder, the timer extracts a clock on each and every active edge and adjusts the counting direction depending on the relative phase shift between the two incoming signals. The timer counter thus directly holds the angular position of the motor or the potentiometer. The simplest use case for a timer is to provide an internal time-base. This is commonly used by software routines either to provide periodic interrupts or single-shot timeout protection. The timer can also provide periodic triggers to other on-chip peripherals such as the ADC, DAC, and other timers. The update event from the timer, typically on counter overflow, is the usual means to have a software time-base interrupt or to trigger a periodic event. The basic timers, Tim6 and Tim7, are best suited for such a task as they are the simplest timer derivatives with no input output channel. It is also possible to generate internal timings using any other timer using compare events or using the trigger outputs on any other timer. It is possible to generate multiple timing events with a single timer using multiple compare channels. This slide describes the input capture features. Each channel can be individually configured as an input capture with a number of signal conditioning options. An input can be mapped on two capture channels, typically to differentiate rising edge from falling edge capture. The edge sensitivity is programmable and can be rising edge, falling edge, or both edges. An event prescaler allows capture of one event every two, four, or eight events. This decreases the CPU burden when processing high-frequency signals and allows the measure to be more accurate since it is performed over multiple input signal periods. Spurious transition events due to noise or bounces can be removed using a programmable digital filter. The figure shows how a signal is filtered when the filter acceptance is set to four. In the upper case, a clean rising edge capture is triggered four sampling periods after the rising edge, as one can notice looking at the internal counter value. In the lower case, a glitch causes the filter counter to be reset and the capture to happen after four successive samples at high level have been counted. Once the capture trigger is issued, the timer's counter is transferred into the capture counter and an interrupt or a DMA request can be issued. If a new capture occurs before the previous one had been read, the capture register is overwritten and an overcapture flag is set for the software to manage this condition if needed. This slide presents some more advanced capture related functions. The clear on capture mode causes a counter reset immediately after the capture has been triggered. This allows a direct measurement of the period while a traditional free running counter would require additional computation to obtain the period following the trigger. In PWM input mode, the timer is able to capture both the period and the duty cycle of an incoming PWM signal. The input signal is internally routed to two capture channels. The signal's rising edge is captured on input capture two to provide the period value with the clear on capture mode. The falling edge is captured by the capture one channel, which provides the pulse length duration. The duty cycle then simply corresponds to the ratio between input capture one and input capture two. Lastly, the timer includes an XOR function to combine the three input channels with XOR logic. This is typically used to handle the three 120 degree phase shifted signals coming from the hall sensors in electrical motors. This allows you to have a clear on capture happening on each and every edge three signals and have a capture value directly usable for speed regulation. This slide presents the output compare features. A compare event is generated when the counter matches the value of the compare register. This event can trigger an interrupt or a DMA request and can be reflected on the corresponding output pin by an output set, output reset or output toggle. The compare register can be preloaded. Preload must be disabled if multiple compare values must be written during accounting period. On the contrary, the preload mode must be preferred for applications with real time constraints since this gives a higher time margin for the software to update the compare register with the next value. The transfer from the preload to the active value is triggered by an update event when the counter overflows or underflows. The output compare mode can also be preloaded so as to allow glitchless transition from a PWM mode to a forced on or off state for instance. One pulse mode is used to generate a pulse of a programmable length in response to an external event. The pulse can start as soon as the input trigger arrives or after a programmable delay. The compare one register or CCR one value defines the pulse start time while the auto reload register or ARR value defines the end of pulse. The effective pulse width is then defined as the difference between the ARR and CCR one register values. The waveform can be programmed to have a single pulse generated by the trigger or to have a continuous pulse train started by a single trigger. One pulse mode also offers a re-triggerable option. In this case a new trigger arriving before the end of the pulse will cause the counter to be reset and the pulse width to be extended accordingly. This slide presents some of the PWM modes. The standard edge aligned PWM mode is programmed with the auto reload register defining the period and the compare register defining the duty cycle the counter being in up only or down only counting mode. A single timer can generate up to four PWM signals with independent duty cycles and identical frequency. When multiple PWM waveforms are generated by the same counter all falling edges occur at the same time hence the term edge aligned. On the contrary the rising and falling edges of center aligned PWMs are not synchronized with the counter rollover so that switching time varies with the duty cycle value. This is achieved by programming the counter in up down mode. This mode is interesting as it spreads the switching noise when multiple PWMs are generated with the same timer. This is a key feature for three phase PWM generation for electric motor drives since it allows you to double the frequency of the current ripple for a given switching frequency. For instance a 10 kilohertz PWM will generate inaudible 20 kilohertz current ripple. This minimizes the switching losses due to the PWM frequency while guaranteeing silent PWM operation. A variant of the center aligned mode is the asymmetric PWM mode where two compare registers define the turning on and off of the PWM signal. This provides higher resolution for pulse width setting since turn on and turn off times are individually defined. It also allows the generation of phase shifted PWM signals necessary to drive DC to DC converters based on the full bridge phase shifted topology. In this case the timer provides two PWM signals with identical frequency, 50% duty cycle and a phase shift varying from 0 to 180 degrees. This slide presents the combined PWM modes. This mode allows a logic combination of two PWM signals to be generated by adjacent channels, output compare 1 and 2 or output compare 3 and 4. The PWMs can be OR-ed or AND-ed to create complex waveforms. Typically this allows you to have two periodic pulses generated with any pulse width and any phase relationship value. The combined three phase mode specifically targets three phase motor control applications. In this case channel 5 of the timer can be combined with any of the three channels 1, 2 or 3 to insert a low state in the middle of a centered pattern PWM signal. This mode greatly simplifies the implementation of low cost current sensing techniques for three phase motor control using a technique usually referred to as zero vector insertion. This slide presents some more specific PWM modes where either the frequency or the duty cycle can be driven by external signals. The timer can provide variable frequency signals using an external reset signal connected either on the ETR or on the channel 1 or 2 inputs. The purpose of this mode is to provide a signal with a fixed on or off time and a continuously adjusted frequency controlled by the hardware. The timer provides control for the on or off time using the compare register while the auto reload register guarantees that the PWM will not stop if the external reset is missing thus providing a safe control in boundary conditions. This technique is used for a variety of purposes such as transition mode PFC or power factor controller for mains supplied applications and current controlled digital LED lighting. Another mode for the timer is to have the duty cycle controlled by hardware with either an on chip comparator or an off chip comparator. The PWM is operating at fixed frequency with maximum duty cycle being set by the compare register and the actual value controlled cycle by cycle. This is used for applications requiring current controlled PWMs typically for driving DC motors or solenoids. In this case a comparator monitors the peak current value into the load. As soon as the current exceeds a program threshold the comparator resets the PWM output which is then automatically restarted at the next PWM period thus providing a controlled peak current value. This slide presents the timer's synchronization features. The trigger controller allows you to cascade multiple timers in a master slave configuration. A timer can control one or more timers as the master timer or be controlled by another timer as a slave. The clock and trigger controller acts as a link between the timers. In master mode it can redirect outside the timer multiple internal control signals to an on-chip TRGO trigger output. In slave mode it gathers multiple inputs on TRGI the main trigger input coming from the external trigger pin or ETR or from one of the four internal trigger inputs ITR1 to ITR4 connected to the other TRGO outputs. Additionally the input capture one and two pins can also be used as an internal trigger typically to reset the counter. The slave and master modes can be programmed independently. A given timer can thus simultaneously be operating in slave and master modes in a cascaded configuration accepting input triggers while providing output triggers. This slide lists the various operating modes and the signals exchanged between timers. In master mode eight options are given for selecting the trigger to be sent on the TRGO output. The output can be a single synchronization pulse issued upon counter reset, counter enable which corresponds to the counter start, the update event, or the compare one match event. Alternatively the TRGO output can also transmit one of four waveforms generated including PWM signals to the other timer modules. In slave mode the timer operating mode is controlled by the TRGI input. In triggered mode the counter start is externally controlled. This mode is used for simultaneously starting multiple timers. In reset mode the counter is reset by a rising edge on the TRGI input typically for variable frequency PWM operation. A combined mode including reset and trigger can be used for re-triggerable one pulse mode generation. In gated mode shown in the figure the counter is active only while the level on the input signal is high. This signal is either coming from an input or from another timer in waveform generation mode. In this case synchronization pulses issued on reset, enabled, update or compare match cannot be used. Lastly the slave mode selection includes clock related modes such as quadrature encoder decoding or external clocking modes mentioned earlier in this presentation. This slide gives two examples of synchronized operation. The first example shows how four timers can be simultaneously started. A mechanism allows the master timer to start slightly delayed to compensate for the master slave link delay and have all timers synchronized with cycle accuracy. By combining the channels of timers 2, 3, 4 and 15 as shown it is possible to have up to 14 synchronized PWM channels. The second example shows how to create a 48-bit timer by cascading three timers. Here the update event generated on counter rollover is used as the input clock for the following slave timer. So that timer 3's counter holds the least significant 16-bits timer 2's counter holds the medium bits bits 16 to 31 and timer 15 holds the upper bits from bit 32 to bit 47. This slide summarizes the timers four main electrical motor control features. The timer includes specific PWM modes for controlling power switches. In addition to center aligned and combined three phase PWMs previously described, the timer features dead time insertion for complementary PWM generation and six step mode for driving brushless DC motors. It includes power stage protection circuitry with a dual level emergency stop mechanism to disable the PWM outputs by hardware in case of a fault. It is able to handle the most common sensors found in motor control systems. Quadrature encoders and hall sensors are used for fine and coarse position feedback while tachometer generators are used for cost effective speed feedback and just require a clear on capture mode. Lastly the timer includes synchronized ADC triggering options necessary to properly manage voltage and current sensing and avoid any acquisition issues due to switching noise in power stages. This slide presents the dead time function. A hardware dead time generator provides two non-overlapping complementary PWMs from a reference PWM signal. The STM32 timers include up to three dead time generators for OC1, OC2 and OC3 channels. The dead time duration is programmed with an 8 bit value. This value can be locked by the user to prevent this critical value from being corrupted during run time. This is done by setting a right once lock bit which switches the dead time register into read only mode until the next MCU reset. Dead time insertion is necessary when driving half bridges where a pair of transistors are connected in series between two power rails. In this case it is necessary to insert some time before the switch on of one side to allow the other side to switch off taking into account physical switching characteristics. Half bridges are usually found in DC to DC converters for DC or stepper motor drive using the full bridge topology shown here for three phase inverters with three PWM pairs. This slide shows how the six step drive also called block commutation is managed with the STM32 timer. It consists of chaining two timers, one handling the three hall sensor signals while the other manages the PWM generation synchronized with rotor angular position generating six successive steps. The first timer operates in clear on capture mode triggered by the three inputs. A compare register here compare two is responsible for adding a programmable delay between the raw angular position and the commutation time. The capture register one holds the timing interval between successive hall sensor edges and is necessary for the speed regulation loop. The compare two match event is propagated to the slave timer through the TGRO output. These events serve as commutation events and trigger changes for PWM generation. For each of the six steps of the sequence, the states of the six outputs are defined to be either forced active or inactive or generating a PWM signal. The transition from one step to the other is preloaded by software in the commutation interrupt routine and automatically transferred by hardware to reprogram the output operating mode when the next commutation arrives. The figure at right shows the six PWM signals for two consecutive complete six step sequences together with the current in one of the motor phases. This slide presents the break function. A break event triggers a hardware protection mechanism that automatically disables the PWM outputs and forces them to a user configurable state either low impedance with high or low level or high impedance. The logic circuitry works asynchronously without any clock. This guarantees the functionality even in case of a system clock failure and avoids any clock related propagation time that would tend to delay the protection. This feature is available on all timers having complimentary PWM outputs which are capable of performing power conversion tasks on timers 1, 8, 15, 16, and 17. Timers 1 and 8 have two separated break channels. This provides a dual level protection scheme where for instance a low priority protection with all switches off can be overridden by a higher priority protection with low side switches active. Furthermore a dead time delay can be inserted immediately before entering the fault mode for safely disabling the power stage. This prevents potential shoot through conditions. Let's consider for instance that the fault occurs when the high side PWM is on while the safe state is programmed to have high side switched off and low side switched on.  This slide presents how the break function sources are managed. Multiple break sources can be combined for triggering a break event. Five system level sources can be selected. The core lockup Cortex-M4 internal error, the PVD or programmable voltage detector under voltage error, the SRAM parity error, the flash memory ECC error, and the clock security system or CSS indicating an external clock failure. All these features can be individually selected including the CSS. Break inputs can also be detected with the alternate function controller on the MCU pinout. Last, the two comparators and the digital filter or DFSDM can also serve as emergency shutdown sources when they detect out of range signals. External sources or on-chip comparator signals can be conditioned before entering the break detection unit. This allows selection of the proper polarity and discarding of spurious glitches by means of a digital filter. Besides the regular digital break inputs and internal break events coming from the comparators, Timers 1 and 8 feature bi-directional break inputs and outputs combining the two sources as shown in the figure. These pins combine the comparator output configured as open drain and the timer's break inputs. With a single pin, they allow global break information to be available to external MCUs and external gate drivers to shut down the inputs. This also provides the option to have an internal comparator and multiple external open drain comparator outputs to be ordered together and trigger a break event when several internal and external break inputs must be merged. This slide presents the ADC triggering options related to the timers. The ADCs can be triggered with most of the STM32 timers with three options. This can be done using compare events. The ADC conversion will start on a given compare frame. The list of supported compare events varies from one timer to the other as shown on the table. The TRGO event can also be used on certain timers. This gives extra flexibility since the TRGO can be any of the compare events or timer internal control signals such as register update, counter reset or trigger input. On the other hand, this prevents the TRGO from being used for synchronization purposes. For this reason, timers 1 and 8 also have an additional TRGO 2 output fully devoted to ADC triggering. TRGO 2 offers 16 possibilities including the six compare events and the possibility to have a dual trigger per PWM period by combining the compare 4 and 6 events. This also leaves the TRGO free for multiple timer synchronization schemes. This slide presents an example of PWM synchronized ADC trigger. For a three phase motor control, it is mandatory to have ADC readings synchronized with the PWM generated for controlling the power stage. This allows extraction of the average value out of the current waveform ripple and make sure the ADC reading is done at an adequate distance from the ringing due to the power switches. Shown here on the left is a three phase motor inverter. The six switches are controlled by three complementary PWM pairs with dead time inserted. While the current in the motor windings is measured using shunt resistors placed in the three half bridges bottom side. The right side shows the timers counter compare 1 and compare 2 values and corresponding PWM outputs for the low side switches controlled by CH1N and CH2N. The two bottom waveforms represent the current in the motor phase and the image of this current obtained on the shunt resistors. With this low cost topology the voltage can only be measured when the low side switches are on which explains the square wave shaped signal obtained on the ADC input. In this case the ADC trigger is generated on the counter rollover. This allows the reading to be done precisely in the middle of the period and get the average value of a signal with a significant ripple. Additionally, using a PWM synchronized ADC trigger also guarantees that the ADC conversion will be done away from the ringing noise present on the shunt voltages. This slide lists the interrupts and DMA requests sources. Most of the events are able to generate either an interrupt or a DMA request and even the two simultaneously. The update is issued when the counter overflows or underflows. This allows to refresh the timer's runtime settings at the beginning of the PWM period and maximize the interval before the next register update. The repetition counter allows you to skip some PWM periods and decrease the number of interrupts or DMA requests at high PWM frequency. Each of the four capture and compare events have their own interrupt and DMA. A trigger event on TRGI input regardless of the trigger source can also trigger an interrupt or DMA request. Lastly, additional sources of interrupts and DMA requests are the commutation and break events on timers 1, 8, 15, 16, and 17 only. Note that the break event does not generate DMA requests. The timer includes a DMA burst mode to have multiple registers reprogrammed with a single DMA stream. This allows the modification of several runtime parameters simultaneously, for instance duty cycle and frequency of several channels, or dynamically change the timer configuration by writing the configuration registers. The example shows how a table containing three compare values can be transferred into the compare registers with a single DMA stream when a new PWM period starts. The DMA must be programmed in memory to peripheral mode, pointing to a unique location in the timer, virtual register, Timx underscore DMA-R. When the update event occurs, the timer sends a number of DMA requests corresponding to the programmed burst length. Each value is then automatically redirected from the virtual register into the active register targeted. On the next update event, three new compare values are transferred again. In this example, this mechanism saves two DMA streams that would normally be necessary for such an update scheme. The timer is active in any of the run and sleep modes, while it is frozen in stop mode. The timer state and register content are preserved and the timer directly resumes operation when the MCU is awakened. In standby and shutdown modes, the timer is powered down and must be completely re-initialized when exiting from these modes. The timer state in debug mode can be configured with one configuration bit per timer. If the debug bit is set, the timer clock is maintained during a break point. If the debug bit is set, the timer's counter is stopped as soon as the core is halted. Additionally, the outputs of the timers having complementary outputs are disabled and forced to an inactive state. This feature is extremely useful for applications where the timers are controlling power switches or electrical motors. It prevents the power stages from being damaged by excessive current or the motors from being left in the state when hitting a break point. This slide explains how to set the timer's PWM frequency. This parameter is defined using the auto-reload value, or ARR, programmed in the TIM-X-ARR register and the clock pre-scaler programmed in the TIM-X-PSC register. The PWM frequency is given by the timer operating frequency, FTIM, divided by ARR plus 1 times clock pre-scaler plus 1. Practically, finding both register values is an iterative process where one must start from PSC equals 0. In other words, no clock division. This guarantees that the PWM will have the finest possible resolution. In this case, the ARR value is simply the ratio between the timer clock frequency and the PWM frequency, the whole minus 1. If this equation yields an ARR value above the timer's ARR range, either 16-bit or 32-bit, depending on the selected timer, the computation must be redone with a higher pre-scaler value with the following sequence. An ARR value equal to timer clock frequency, divided by 2 over PWM frequency, the whole minus 1, then an ARR value equal to timer clock frequency, divided by 3 over PWM frequency, the whole minus 1, and so on up to the point where the ARR value fits within the programmable range. This slide explains how to program a duty cycle for a given PWM frequency. This parameter is defined using the auto-reload value, or ARR, programmed in the TIMEX-ARR register and the compare value programmed in the TIMEX-CCR-X register. The duty value does not depend on the PWM frequency and is given by compare value plus 1 over the auto-reload value plus 1. Another useful indication is the PWM resolution. This gives the number of possible duty cycle values and indicates how fine the control on the PWM signal will be. The resolution, expressed in number of duty cycle steps, is simply equal to the ratio between the timer clock frequency and the PWM frequency, the whole minus 1. Another way of expressing it is in bits, as for giving a DAC converter output resolution. In this case, the resolution is the base 2 logarithm of the ratio between the timer clock frequency and the PWM frequency, the whole minus 1. This slide shows a simple practical example of PWM usage, for dimming a low power LED. This can be done directly using a PWM output, as long as the current does not exceed the rated output current. The first step is to program the frequency to be set to 1 kHz. When doing the ARR value computation with no prescalar and a timer operating frequency of 80 MHz, the value obtained is 79999, which is above the 16-bit range that can be used with timer 1. The timer prescalar must be set to 1 to have the timer operating at 40 MHz, and this results in a valid value of 3999 for the ARR register. The second step consists of computing the register value to have a 20% duty cycle. This yields a value of 7999. Lastly, the dimming resolution can be computed from formulas presented in the previous slides. With a timer running at 40 MHz, a 1 kHz PWM provides 40,000 dimming steps, which corresponds to an equivalent resolution of 15.3 bits. This slide explains a common support case, where the whole timer is configured, the PWM mode is enabled as well as the corresponding outputs, but still there's no activity on the pins. Usually this is because the MOE bit was not set. For timers equipped with dead-time generators, timers 1, 8, 15, 16 and 17, a main output enable or MOE bit in the TIMEX BDTR registers, controls all outputs, and acts as a circuit breaker in case of fault detection on the break input, global disable of all PWM outputs. The MOE bit must be set or armed to have the outputs enabled. This is valid even if the timer is used without dead-time insertion, and the timer is used for general purpose applications. The timer is linked with multiple on-chip peripherals. It serves as a trigger source for the ADC and the DAC converter. It also receives signals from the ADC's analog watch the comparator or the DF-STM filter that can be used to shut down PWM signals. This slide lists the timer instances present in the STM-32L4. Timers 1 and 8 are full-featured timers, motor control capable, including all PWM options and six compare channels for being able to simultaneously generate three-phase PWM signals and have two independent ADC triggers. Timers 2, 3, and 4 are general-purpose timers, including all PWM modes, up-down counting capability, and four channels. Timers 2 and 5 additionally offer 32-bit counting range. Timers 15, 16, and 17 are light timers with support for standard PWM only with one or two channels and up-counting mode only. They complement the other timers whenever additional independent time bases are necessary. They also have dead time insertion and break input for driving simple power systems with one PWM pair only. Lastly, timers 6 and 7 are pure time bases with no outputs, aimed principally to trigger the DAC converters or to provide software time bases. Three application notes complement the timer sections in the reference manual. AN-2592 gives a practical timer made of two synchronized 16-bit timers and is useful for better understanding the overall timer synchronization mechanism. It comes with a software example. AN-4013 provides a more detailed overview of all timer features and available firmware examples. AN-4507 presents an implementation of PWM resolution enhancement by means of dithering techniques. It comes with a software example.


Al Pacino, Keanu Reeves, Shirley Theron movie, The Devil's Advocate. Anybody ever seen The Devil's Advocate? Quite a movie, quite an intense movie. But in the movie there's all these temptations. Al Pacino plays the devil quite well. All the things that Jesus talks about in the Course in Genius and all these things. Al Pacino really is an amazing performance. And Keanu Reeves and Shirley Theron are in a relationship. They go through enormous temptations for everything. Greed, power, pleasure, status, the whole deal. And winning in the courtroom, not losing a case, competition. It's got the whole thing in there. And basically there's just enormous temptations that they seem to go through. At the very end it's like they're talking in the restroom and there's this other lawyer talking to him. And he's kind of come back full circle to where he was at the beginning. And then the other lawyer just morphs into Al Pacino. And Al Pacino says vanity. Get some every time. That's like the eighth pride in the vanity. That self-recognition that, you know, look at me or look at what I've done or, you know, putting an emphasis onto something on the timeline. Even a story or something that's supposed to, you know, have you stand out a little bit more than the rest. Which is where the hierarchy thing comes in. And wanting to be different. Even though the Course keeps telling us, make this year different by making it all the same. It keeps encouraging us to go for sameness. Saying sameness isn't boring. It's not monotonous or anything. It's actually quite joyful to have perfect equality to see everything and everyone the same. And also it says it takes lots of mind training. So what's happening is, you know, you give yourself over to a desire to really practice the Course and live the Course and transfer the training, like the workbook talks about.  That desire for recognition. That desire to be just a little different. Just to be a little distinguished from the rest. And that's why we're giving a curriculum, really, to teach what we would learn and to practice and practice and practice so much that it's part of like a rinsing that goes on in the mind. You know, where you have more of that experience like Ana was talking about that experience where you don't know where, you said, I don't know where I begin and where anything ends. There's no end. It's just a vast experience. You've been having a lot of those kind of vast, vast experiences and everything. And those are like glimpses.  You get a glimpse of the happy dream of the forgiven world.  And yet, the core of the training and the practice is to put the purpose out front, to come into an awareness of a purpose, you know, in terms of willingness for what, readiness for what, mastery through love of what, of changing your mind about your mind, of changing your mind from believing that you are an ego, changing your mind from believing that everything is changing to an experience of the constancy of divine mind to the constancy of spirit to the unchanging quality of spirit. You know, that's the course of saying you have to change your mind about your mind. And that, you start off thinking, how will I accomplish that? Well, the Holy Spirit is the only way that that gets accomplished. You may think of changing your behavior.  That is more of, you know, tinkering with the deck chairs and the Titanic, you know, just moving the chairs around. All of that. It's so important in this world, self-improvement, self-help books, you know, be all that you can be. And all this in terms of like the Army or some kind of a program of self-improvement, you start to realize that all of that is still involving pride and is still trying to come up with a better self instead of opening humbly and seeing that God created me perfect. And maybe I just need to release and forget everything that I've been trying to do to improve upon that perfection. So it's, you're on for, it's a deep journey and really the one right use of judgment is how do you feel. You know, when you feel just a little bit closed off or maybe even when you notice that need for attention, you notice that underneath that there's like a sense of neediness or a sense of needing to prove something or prove worth or demonstrate worth or whatever. And this whole curriculum is designed to show you that you don't have to go down that road anymore. And anything that it seems to involve that anything is with people or public or whatever, you just have a lot of mirrors.  And so you pay attention and you notice and you notice and you notice and you just trust that you'll be carried through into that purity and that innocence. That's what you're really here for.