[beagleboard] Booting BeagleBone Black without a Power Button

2017-10-11 Thread Joe Kleespies 
Hey All,

I'm in the process of designing a custom version of the BeagleBone Black. 
In my application, I don't want a power button. I'd like the board to boot 
as soon as the AC or USB signal is energized on the PMIC. I know that, by 
default, the BeagleBone Black looks for the PB INT bit in the PMIC INT 
register before asserting the PMIC_PWR_EN. In my application, I assume I'd 
need to modify boot code to look for the AC or USB INT bits in the PMIC INT 
register. My question is whether or not this requires a modification of the 
SPL or if the processor handles this in the primary boot code in ROM.

Any advice is much appreciated.

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[beagleboard] Modifying BeagleBone Black Boot Code to Eliminate Power Button

2017-10-10 Thread Joe Kleespies 
Hey All,

We're in the process of making a custom version of the BeagleBone Black. 
Because this is a custom board, I assume that some sort of boot code needs 
to be flashed to the processor ROM, which handles initial booting of the 
processor before passing control to an image in eMMC or SD. Does anyone 
know where this primary boot code for the BeagleBone Black can be found and 
how it is flashed to the processor?

Also, in our application, we don't want a power button. We'd like the board 
to begin booting as soon as power is applied on either the AC or USB inputs 
of the PMIC. I assume that, by default, the BeagleBone Black boot code 
reads the INT register on the PMIC and asserts the PMIC_PWR_EN line only 
when it reads a set PB INT bit. We'd like to modify this code such that the 
processor asserts PMIC_PWR_EN when it reads the AC or USB INT bits.

Does anyone know where the boot code can be found and where it should be 
modified to suit this application?

Thanks in advance,

Joe

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