EHRPWM1A and 1B in Debian Jessie 4.1

Hello All,

I’m using Kernel 4.1.18-bone-19 in Debian Jessie. I’ve got my LCD cape running currently and I’m happy with how the backlight is functioning on EHRPWM1A. I currently have a piezo buzzer attached to EHRPWM1B, and I can’t for the life of me figure out how to get the PWM to work on the second channel.

I’ve been using the cape-universal overlay that has been modified to remove the pins that I’m using for my UART2 cape and my LCD4 cape. The trouble with this approach is that it exports all PWM options, and I’m not sure which one I need to use.

My guess for the PWM chip to use is pwmchip4. This is because when I try to export pwm0 it tells me it is in use, but it will allow me to export pwm1. This is pure speculation that I’m even using the right channel. I don’t know enough about this OS to find out which pin is mapped where (still new to this environment).

I’ve been following the instructions here: https://groups.google.com/d/msg/beagleboard/dkS51WbicTo/tZ13PZChCgAJ to try different PWM channels.

I’ve been through all of the pwmchips (0, 1, 2, 4, 6) and none of them trigger my piezo buzzer. pwm1 in pwmchip4 is particularly nasty, it won’t let me export a period or a duty cycle, it just says that the arguments are invalid.

There don’t appear to be many tutorials on how to use PWM in the 4.1 kernel, and even fewer examples on how to use EHRPWM1A and EHRPWM1B simultaneously, although from what I’ve been reading it should be possible.

Any thoughts/pointers/help is appreciated.