bbb-pwm

python pwm for the beaglebone black

This PWM library overrides the hardware specifics of pwmpy to allow its use with the BeagleBone Black.

On BBB, the PWM related sysfs filenames in version 4.4 (and others?) of the linux kernel can sometimes change with reboot. This library sorts out the sysfs filenames and allows access to the pwm devices using pwmpy by device name rather than chip/channel definition.

The little snippit of code that adapts to the shifting filenames is thanks to samual.bucquet. The rest is just dressing.

dependencies:

Scott's pwmpy class which handles the sysfs interface.

installation:

copy pmwpy.py to your work folder.
copy bbb_pwm.py to your work folder.

two methods of use are:

as a class
```
import bbb_pwm
pwm = bbb_pwm.PWM("EHRPWM0A")
```
The user mananges the opening and closing of the resource and handles any events appropriately to ensure the pwm device is left in the state desired on program exit.
as a context handler
```
import bbb_pwm
with bbb_pwm.PWM("EHRPWM0A") as pwm:
```
The context manager handles the opening and closing of the resource and makes a best effort to cleanup/shutdown any pwm resources used.

If the user either doesnt care or intends that the pwm is left running after program exit, then used as a simple class may be appropriate. Otherwise, use as a context handler to ensure pwm's are off and unexported if an exception should happen to trickle to the top.

See cape expansion headers for pwm device names.

caveat:

this library assumes that altho the pwmchip file suffix values may change, the order of the pwmchip filenames does not.

TODO: