Hardware PWM using lightweight rpi_hardware_pwm library

[shortbloke]

Lightweight hardware PWM implementation with GUI configuration, allowing 25000 Hz PWM signal suitable for controlling Noctua PWM fans.

Another PR #442 but was criticised for needing pigpio and lacking UI configuration. This PR attempts so address the requirement whilst:

• Using a lightweight rpi-hardware-pwm library not pigpio
• Does not require everyone install the library, only if you enable this option in the UI

Fixes: #349

[GerhardMassenbichler]

Great Work. I like the small and lightweight rpi_hardware_pwm library instead of pigpio.

[pipersw]

Could you provide a binary for Raspbian ?

[joh]

Hi, what remains for this PR to be merged? :)

[joh]

Just tested this and it works great, thank you! Only snag was that installing rpi-hardware-pwm system-wide (as per instructions) didn't work on OctoPi, since OctoPrint runs in a virtual environment and won't see system-wide packages. Instead I had to install it in the virtual environment, like so:

source ~/oprint/bin/activate
pip install rpi-hardware-pwm

Perhaps the docs can be updated, or even better, that the package can be installed on demand by the plugin?