[FEATURE] Support 6-channel PWM with only TC4 on ATmega32u4

[cinderblock]

I'd like to use some existing ATmega32u4 based driver boards. Theses are wired up to the 6-channel PWM output that is unique to the ATmega32u4's 10-bit High Speed Timer/Counter4.

AVR Pin	Output Compare	Arduino Pin
PC7	OC4A	D13
PC6	OC4A~	D5
PB6	OC4B	D10
PB5	OC4B~	D9
PD7	OC4D	D6
PD6	OC4D~	D12

Looking at the sources in atmega32u4_mcu.cpp, it's clear that the code is only set up for a couple dedicated pins that don't fully overlap with the Timer 4 hardware outputs.

I realize this is an older IC but is there any interest in supporting this mode?

My very old implementation: https://github.com/cinderblock/3-Phase-Controller/blob/master/src/ThreePhase/Driver.cpp

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PS, great to meet you at OpenSauce!

[askuric]

Hey, this could be a nice addition, would you be interested to do a PR for this?

[cinderblock]

Yes, I'm interested. But I won't have time to look much at this for the next 2, maybe 6+ weeks! (Moving offices, Burning Man, traveling to a wedding) So if anyone else wants to get started, be my guest!

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To be sure, would this (new) code live in this repo or in the drivers repo?

[runger1101001]

From my point of view it would be one of the PWM drivers in the main repository, or a modification to one of the existing AVR drivers…

[askuric]

Yep, I agree. This would go the the main library inside the file atmega32u4_mcu.cpp.
I am going to try to provide you with a starting point @cinderblock, maybe even implement it completely, if I manage to get the time. Otherwise, don't hesitate to contact us when you start implementing it if you need some assistance.