I have this problem with my bbb:
I have two DACs made of ressistor ladder connected to pins P8 39-46 (PRU1_0 - PRU1_7).
When I try to power on my bbb and the DACs are connected then bbb doesn’t boot. Only
power led is on (next to the DC barel). Serial output also doesn’t print anything at all.
Just to elaborate a bit the Dacs are not actually connected to any output during boot, so just the pins
are connected via resistors (4K, 2K, 1K, 500ohm).
The schmeatics looks like this:
o----[4k]---------±--------> out —> 75 Ohm —>GND
When I unplug the DACs my bbb boots normally. Serial output prints kernel messages etc. so everything is fine.
Is this expected? If not, what can be the issue ? If yes, do I have to use some sort of switch on/ off
mechanism that will disable my DAC during power on to let bbb to boot ?