I think there are only three PWM units (ehrpwm0, ehrpwm1, and ehrpwm2), but two of them have an A and a B. I didn't dig too far, but I suspect there are some constraints on how the A and B can be used, such as maybe they have to both be at the same frequency, but they could have different duty cycles. The question about which pwmchipN to export is a good one, and I think this is where the documentation is the weakest. I think that when I had all the PWMs enabled in the device tree, ehrpwm2B was pwmchip6. I think it just starts with a base of zero and increments for each enabled pwm unit. When I only had ehrpwm2A enabled, I saw only pwmchip0, so I knew that was it. An remember, you are not exporting the pin, but the PWM itself, to user space. I finally realized that's what 'export' means. The pinmux table handles the routing of the PWM output to the physical pin. I'm pretty sure you are right about P8_13 and P8_19, but I don't recall the other ehrpwm pins. I found these tables ( http://www.embedded-things.com/bbb/beaglebone-black-pin-mux-spreadsheet/) by googling "beaglebone black pin mux table".
On Thu, Oct 1, 2015 at 2:13 AM, Khanh Nguyen <[email protected]> wrote: > Hey Kevin, > > Thanks for the guide on enabling PWM on kernel 4.1. I'm a little confused > with PWM now though,...Based on the values that you provide, are you saying > that, there are only 3 PWM's on the Beagleboard? I thought there were more > than that or maybe I was wrong. > > The 2nd question would be, is this right? > > 0x024 0x4 corresponds to ehrpwm2B = P8_13 > 0x020 0x4 corresponds to ehrpwm2A = P8_19 > 0x150 0x3 corresponds to ehrpwm0A = P9_14 > (Are we missing some pins) > > Also, how do you know it's pin 0 to export? I thought this were more like > exporting GPIO, whereas you'd need to know which pin is which to export? > > Thanks, > Khanh > > > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to a topic in the > Google Groups "BeagleBoard" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/beagleboard/dkS51WbicTo/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- 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]. For more options, visit https://groups.google.com/d/optout.
