Setting GPIO Values "from cold" startup???


I’m developing a system that uses PRU 1 to send a PWM to a switched mode power converter.

When I first turn the system on, I want the PWM signal to be low. If the pin is high, I will pretty much surely blow my mosfets as current surges through my circuit.

For some reason, when I first turn things on the pin runs to high… I’m not sure why.

This is before I start messing around with the device tree or anything. Cold boot. I apply power and even before the LEDs light up I can see that the pin in question runs high.

Is there anyway I can control this behavior?



The datasheet tells you the default for all the pins on power up. Some are high and some are low. Until the SW changes that, they stay and the preset levels.



Thanks so much.

How interesting! I suppose I can just cold boot the BBB and see which pins are where to figure out where things start, but I would love to read up more on this given that my hardware could get bricked if something were to change.

Since I got your reply I’ve been pouring over the Technical Reference Manual, but I am not able to find a discussion of default pin states anywhere… could you throw me another clue to where I can find this info?

Thanks again.


It is in the Datasheet.


It is in the data sheet, not the TRM.

Table 4-1, columns 7 and 8.



Thanks Gerald.

Interesting that this is not configurable.

Great to know what to expect though.