linux 3.8 PWM guide?

GoogleGroups
21

Just a short comment:

Using Beagleboard bone, and ubuntu 3.8 with kernel:

  • Linux ubuntu-armhf 3.8.13-bone28: pwm IS working
  • Linux ubuntu-armhf 3.8.13-bone20: pwm is NOT working

Probably because the driver (pwm_test.ko) is not included

  • MBA
22

and for some reason, users seem to not want to upgrade from bone20 to
bone28... Not sure why. :wink:

Regards,

23

Just my two cent,

after some struggling with the eQep support

I’m currently using BBB with 3.8.13-bone28 xenomai patched and both of PWM and encoder reading are working well.

24

what did you do to get it to work on the new kernel? did you simply follow the steps here:

modprobe pwm_test
echo am33xx_pwm > /sys/devices/bone_capemgr.9/slots
echo bone_pwm_P9_14 > /sys/devices/bone_capemgr.9/slots
echo 500 > /sys/devices/ocp.2/pwm_test_P9_14./period
echo 250 > /sys/devices/ocp.2/pwm_test_P9_14./duty

?

25

Was this using Ubuntu?

26

Yes I’m using Ubuntu 13.04 as my userland.

It is working faily well but sometimes (once in a second) I have latancies that approaces 1 ms… I’m reasoning about writing a xenomai kernel space driver for PWM/eqep…

27

Is it because of the pwm_test.c that kind of thing?
I’m just don’t know what’s the connection between the device overlay tree and c/cpp driver?