On Mon, Apr 18, 2016 at 8:12 PM, Greg <[email protected]> wrote: > I'm trouble shooting a problem on a simple cape for a BeagleBone Black. > > I have a bipolar switch for an LED, very similar to that used for the "User > LEDS". > So I have added an approximately 10Kohm load to one of the "boot pins", > which > in header lingo is P8_44. > > P8_44 is also one of the "boot" pins. I'm interesting in using the PRU > connection mode of this pin. > > The System Reference Manuals says the boot pins must not be driven prior to > coming out of reset (SYS_RESET goes high). > > So maybe my understanding of the term "driven" in this context is incorrect, > and it could also be interpreted as "loading", > as in excessive resistive loading? > > I tried an experiment on both BBB and BBG with a 10kohm resistor to ground > on P8_44. Both refused to boot up and run. > So is it a requirement to keep resistive loads off this pin during the boot > process? > > Regards, > Greg >
Yes. You should avoid applying any voltage to any pin before SYS_RESET goes high, or you'll likely permanently break something. In your case it looks like you are changing the boot pin configuration (maybe it defaults to an internal weak pullup?) and preventing your system from booting. If that isn't what you intended you'll want to avoid loading the pin until after SYS_RESET goes high. What are you trying to accomplish with your cape and that io pin? There are approaches that may let you both use the pin and avoiid changing the boot strapping but it would really help to see the circuit you are trying to use with that pin. Chris -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/CAAPegz1YBbVrb-4Lbvf%3DMS40UjizfZxArtm%3DCRv_EQXc4368Lg%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
