Hi there, I've just gone through this myself, and you've already figured out all you need to know. The pwmchipX mapping can change on boot so you can't rely on the /sys/class/pwm structure. Figure out which address maps the epwmss device you want to use and navigate down the /sys/device tree as you have already posted. i.e. /sys/devices/platform/ocp/48302000.epwmss/48302200.pwm/pwm/pwmchipX
See Roberts response to my question here https://groups.google.com/forum/#!category-topic/beagleboard/software/uAHEiJTkE5E FWIW I found the Technical Reference Manual for the AM335x which has all the addresses for the peripherals here https://blog.dest-unreach.be/wp-content/uploads/2017/07/AM335x-TRM.pdf - it doesn't seem to be on the TI site anymore, at least not that I could find. HTH, James Fitzsimons On Thursday, 22 February 2018 17:58:22 UTC+13, Co M wrote: > > Hi, > > I am using C blacklib to handle some i2c and spi devices. Also I have few > PWM's P9_14 and 16 let's say. > > I learned the hard way that P9_14 and P9_16 are to be found in > '48302200'. For P9_14 for example > > /sys/devices/platform/ocp/48302000.epwmss/48302200.pwm/pwm/pwmchipX > > > > which is a link from > > /sys/class/pwm/pwmchip3/ > > > > became available as pwm0 after echoing 0 to /sys/class/pwm/pwmchip3/export > > as > > root@beaglebone:/sys/class/pwm/pwmchip3/pwm0# pwd > /sys/class/pwm/pwmchip3/pwm0 > root@beaglebone:/sys/class/pwm/pwmchip3/pwm0# ls -l > total 0 > -rw-rw-r-- 1 root pwm 4096 Feb 22 03:14 capture > -rw-rw-r-- 1 root pwm 4096 Feb 22 03:14 duty_cycle > -rw-rw-r-- 1 root pwm 4096 Feb 22 03:14 enable > -rw-rw-r-- 1 root pwm 4096 Feb 22 03:14 period > -rw-rw-r-- 1 root pwm 4096 Feb 22 03:14 polarity > drwxrwxr-x 2 root pwm 0 Feb 22 03:14 power > -rw-rw-r-- 1 root pwm 4096 Feb 22 03:14 uevent > root@beaglebone:/sys/class/pwm/pwmchip3/pwm0# > > > > The blacklib still doing old slot way of finding out which /sys/... files > are matching for P9_14 pwm, going > from symbolic links to some hardcoded PXY->1,2,3 mapping finally to find > out the /sys/class/.../pwm/period.. and such... > > My question is: > > How do I determine which X,Y from /sys/class/pwm/pwmchip*X*/pwm*Y* > maps to (X,Y) of a pwm pin P*X*_*Y* > > Thank you > > > > -- 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 beagleboard+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/4df438c2-3352-4a99-8f3f-044e50957571%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
