BeagleBone PWM Sinking and Sourcing

Hello all,

I have a BeagleBone design I am working on, for interfacing with an external LED light array via the PWM outputs.

The current hardware has all of the LEDs sharing a common 3.3V power source, but the current default PWM setup is to output power to the PWM after the pins have been muxed.

I see that there is a Polarity attribute in the AM335x PWM Driver’s Guide, but I am not clear if that actually changes the current flow or just outputs 3.3V with the inverse waveform. I am thinking about jumpering a GPIO pin to provide the necessary shared 3.3V power between all of the LEDs, but I don’t want the magic smoke to escape from my BeagleBone so I thought I would ask the group first.

So to summarize, using for example a four conductor plug that has shared power, and with each conductor tied to a separate cathode on an LED:

  1. Does the Polarity attribute for the AM335x PWM allow current to flow in the opposite direction?
  2. If so, what are the dangers with jumpering a GPIO to pull 3.3V for that shared power? Should there be current limiting resistors in this design?
  3. What would the appropriate Angstrom filesystem command be to provide power via GPIO?

Thanks in advance