{"action":"created","issue":{"url":"https://api.github.com/repos/grbl/grbl/issues/735","labels_url":"https://api.github.com/repos/grbl/grbl/issues/735/labels{/name}","comments_url":"https://api.github.com/repos/grbl/grbl/issues/735/comments","events_url":"https://api.github.com/repos/grbl/grbl/issues/735/events","html_url":"https://github.com/grbl/grbl/issues/735","id":88369395,"number":735,"title":"Pin13 as \"enable\" with PWM during bootloader is a problem","user":{"login":"lkarlslund","id":8929787,"avatar_url":"https://avatars.githubusercontent.com/u/8929787?v=3","gravatar_id":"","url":"https://api.github.com/users/lkarlslund","html_url":"https://github.com/lkarlslund","followers_url":"https://api.github.com/users/lkarlslund/followers","following_url":"https://api.github.com/users/lkarlslund/following{/other_user}","gists_url":"https://api.github.com/users/lkarlslund/gists{/gist_id}","starred_url":"https://api.github.com/users/lkarlslund/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/lkarlslund/subscriptions","organizations_url":"https://api.github.com/users/lkarlslund/orgs","repos_url":"https://api.github.com/users/lkarlslund/repos","events_url":"https://api.github.com/users/lkarlslund/events{/privacy}","received_events_url":"https://api.github.com/users/lkarlslund/received_events","type":"User","site_admin":false},"labels":[],"state":"closed","locked":false,"assignee":null,"milestone":null,"comments":4,"created_at":"2015-06-15T09:29:06Z","updated_at":"2015-07-02T14:03:53Z","closed_at":"2015-07-02T14:03:53Z","body":"I am currently implementing GRBL on an Arduino Nano 5V 16MHz for a used 80W laser engraver I just bought (with defective controller).\r\n\r\nThe plan is to skip Z-axis completely, by taking it out of the homing cycle.\r\n\r\nAlso the laser can to variable power, but sending PWM to a pin on the laser PSU. It has also both active low enable and active high enable pins. I am planning on using the active high enable pin, so if a wire gets disconnected, at least it fails by turning off the laser.\r\n\r\nUsing \"use direction as enable\" I can get both.\r\n\r\nBut ...\r\n\r\nWhen the arduini bootloader starts, it signals success and waits for firmware upload, meanwhile BLINKING the LED on pin13. The PSU I have assumes that no PWM on power and enable high = FULL POWER.\r\n\r\nSo the laser gets toggled 6-8 times rapidly during boot, which is a disaster waiting to happen.\r\n\r\nI know this is not a GRBL problem, rather a bootloader problem. But the choice of pins is a problem.\r\n\r\nSuggestions are welcome - moving the enable to another pin would solve it, and I can hack the source ot do so. But I'd rather get an official solution, so others can benefit too."},"comment":{"url":"https://api.github.com/repos/grbl/grbl/issues/comments/118043532","html_url":"https://github.com/grbl/grbl/issues/735#issuecomment-118043532","issue_url":"https://api.github.com/repos/grbl/grbl/issues/735","id":118043532,"user":{"login":"chamnit","id":948029,"avatar_url":"https://avatars.githubusercontent.com/u/948029?v=3","gravatar_id":"","url":"https://api.github.com/users/chamnit","html_url":"https://github.com/chamnit","followers_url":"https://api.github.com/users/chamnit/followers","following_url":"https://api.github.com/users/chamnit/following{/other_user}","gists_url":"https://api.github.com/users/chamnit/gists{/gist_id}","starred_url":"https://api.github.com/users/chamnit/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/chamnit/subscriptions","organizations_url":"https://api.github.com/users/chamnit/orgs","repos_url":"https://api.github.com/users/chamnit/repos","events_url":"https://api.github.com/users/chamnit/events{/privacy}","received_events_url":"https://api.github.com/users/chamnit/received_events","type":"User","site_admin":false},"created_at":"2015-07-02T14:03:53Z","updated_at":"2015-07-02T14:03:53Z","body":"@lkarlslund : I'm closing this issue, since there are no other output pins that I can put into pin 13 that won't have this potential issue and pin 13 can only be used as an output due to that LED. IMO, using the spindle PWM as an enable when 0V is read is already a solution. I'll place a disclaimer in the config.h file to make people aware of this potential issue. \r\n\r\nFWIW, I'm still pretty sure that if you flash Grbl directly with a programmer and overwrite the boot loader, so that that is no boot loader, this problem shouldn't exist. You can use the Arduino as a ISP and upload with a programmer option. If you have time, please test this theory."}}