Modifying BeagleBone Black Boot Code to Eliminate Power Button

[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

[Gerald Coley]

Boot ROM code is already in the processor. Nothing to flash.

 

BBB already powers up when power is applied. Power button is for power shutdown.

 

If you are doing  a custom board, it might be a good idea to review the System Reference Manual to get a better understanding of how the board works to help with your design.

 

https://github.com/beagleboard/beaglebone-black/wiki/System-Reference-Manual

 

 

Gerald

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