08-27-2016, 09:11 PM
(08-27-2016, 08:46 PM)AidenH Wrote: Hi,
Today I decided to add a power button to my Pine64. I have a momentary push button switch with a red LED that I got off eBay that I was going to use and I soldered some header wires to use the switch with the EXP connector pins (using pin 5). However, I cannot get the switch to work. It works as a reset switch (using pin 4), but not as a power switch. I also soldered on the included switch to the holes at the front of the board but that does work either. I tired using the System LED pin (pin 2) on the EXP connector for the LED on my button, but that is not working as well. I have the latest release of Ubuntu installed. I don't see what is wrong, the button I have works, but connected to the Pine64 it doesn't? Any ideas?
Hi Aiden
In a nutshell, from my understanding, the power button is of use for two main use cases 1) when you have the battery attached and 2) if you are using an android image. Rest of the time, it will simply confuse and not be of much help. To expand on use case 1, if you don't have the battery connected, the pine 64 will start up... and a few seconds later promptly shut down when it realises there is no battery to be found. With use case 2, the power button can be used to both power on the pine64 (with or without a battery), and also give access to the power off menu... otherwise powering the sucker off will be a bit tricky!
Thankfully, you don't have to worry about switch contact bouncing (which means the pine64 thinks the button is pressed multiple times) as the power management IC has built-in hardware denouncing, so you just give it a tap for a short press, and hold it for a second or two for a long one. There is a third instance you can use it, as if you have linux running, pressing the power button will trigger an event you can have code respond to, but I haven't bothered doing anything with that myself (other than to prove it can work).
With the system LED, that probably doesn't do what you think it does. It's a user programmable LED, and can be controlled just like any of the other GPIO ports. Like xalius demonstrates here.
Hope that clears that up for you. Yell out if you're still confused about anything...
