No timers and PWM functions for AVR

[asmfreak]

References #23.

What are the steps towards enabling support for AVR timers?
Is it manageable to add support for timers to a small handful of devices (like mega328p, mega32u4, mega2560)?

[salkinium]

For any AVR timer code you would implement a new lbuild module in modm/src/modm/platform/timer/avr/ similar (but less complicated) to the existing stm32 timer implementation including Timer instances as submodules (modm:platform:timer:1 etc).
You will want to check the modm-devices AVR data for device specific instances and type of peripheral.

You would limit the module to AVR platforms only, or even further to only the few devices that you want to support, by returning True or False in the module’s prepare step:

def prepare(module, options):
    device = options[":target"]
    if not device.has_driver("tc:tc*"):
        return False
    if device.identifier.string not in ["atmega328p", "atmega32u4", "atmega2560"]:
        return False
    return True

Make sure to provide at least one example for these devices using this timer, otherwise your code may never be compiled on the CI.

As far as the actual C++ API is concerned, modm doesn’t have an interface for Timers, since we’ve always used them for motor control and that application has always been very specific to the hardware. So for the STM32 timers we’ve created a STM32-specific abstraction, which may not be very useful for AVRs. So don’t feel like you need to provide the same interface, if you’ve found something better. For simple use-cases like PWM an architecture interface would be nice to have though.

Just open a PR and we and the CI can guide you along.

[asmfreak]

I'm working on this, soon to release first mwp pr.

[mbait]

What's the status of this? I'm mostly intereste in PWM. If PWM has been already implemented in AVR or if there's another discussion - please, let me know.

[salkinium]

There's one PR with some of the work and then another with maybe some more work:

• WIP: Better AVR support #163
• [avr] Add AVR Timer support via lbuild module #593

They don't seem very complete, but at least it's something to look at.

[salkinium]

There isn't really a Timer interface, so feel free to implement just PWM on just one AVR. There's no need to complete the whole API for every AVR (since that's annoying). Someone else can then continue the work.