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google-coral / edgetpu

Coral issue tracker (and legacy Edge TPU API source)
https://coral.ai
Apache License 2.0
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Automatically switching on Dev-Board Mini with power supplied over GPIO 5V #442

Closed FHermisch closed 3 years ago

FHermisch commented 3 years ago

Hi,

I provide power to the DevBoard-Mini from the GPIOs via our own custom-made PCB HAT (which additionally just features some LEDs and a Fan-Control for an industry-fair showcase). I seams like I misunderstood 5.1.2 of the DevBoard-Mini technical manual - thinking it would power up automatically like having power supplied via USB OTG.

Is there any way to make the DevBoard-Mini boot automatically in this case? - like e.g. having some registers of some I2C chips updated, having a special firmware update (like the one with the 'orange' LED during bootup).

Would be great if there is a software solution, as otherwise we have to reconstruct our casing to spare a hole for reaching that button.

Thanks, Florian

hjonnala commented 3 years ago

Hi Florian,

This is not possible without hardware changes. There are two ways to boot the system, via the power button or via charger detection. If you look at page 5 of the schematic (https://github.com/google-coral/electricals/blob/master/dev_board_mini/Coral-Dev-Board-Mini-schematic.pdf) you'll see the detect signal (VCDT) is only sourced when the USB OTG 5V is applied (VBUS_TYPC). This would need to be reworked in order to tie VCDT to the VBUS on the GPIO connector.

Thanks

FHermisch commented 3 years ago

Hi Hemanth, thank you. As you searched, I also had a look into the schematics. The VCDT you mentioned as well as the PWRKEY signal is connected to the MT6392 chip. The functionality of this chip is steered by a multitude of register settings via system drivers / device tree overlays. Sadly there is no open available documentation of that chip - it might feature some persistent registers which steer the functionality of the PWRKEY as well as the behaviour of "ON POWER" - like every regular PC bios has. If you do have access on these documentations, it would be great if you have a short look. If it is a one-time-setting (like electronic fusing) - this would also be ok for me. Greetings, Florian

hjonnala commented 3 years ago

Hi Florain,

The documentation for MT6392 chip is not open sourced. I have checked with internal team got to know that even the documentation of chip won't help in this case.

Thanks

FHermisch commented 3 years ago

Thanks a lot for checking this!