PwmPin from embedded_hal

[zignig]

Thanks for the cool library Rahix !

Still attempting to get my rust FU together , but programming micros has always been fun.

I am trying to write a differential drive controller. I have got pwm control working in main (using the pwm example mostly).

So .. I have a construct that I am trying to build in a generic struct.

use embedded_hal::PwmPin;

pub struct DiffDrive<E, P1, P2>
where
    E: PwmPin,
    P1: OutputPin,
    P2: OutputPin,
{
    en: E,
    p1: P1,
    p2: P2,
    config: Config,
}

impl<E, P1, P2> DiffDrive<E, P1, P2>
where
    E: PwmPin,
    P1: OutputPin,
    P2: OutputPin,
{
    pub fn new(mut en: E, mut p1: P1, mut p2: P2) -> Self {
        let conf = Config::default();
        Self {
            en: en,
            p1: p1,
            p2: p2,
            config: conf,
        }
    }
}

Constructed with

    // Create the drive parts
    // left drive

    let timer0 = Timer2Pwm::new(dp.TC2, Prescaler::Prescale64);
    let mut pwm_pin = pins.d3.into_output().into_pwm(&timer0);
    let mut en_pin1 = pins.d8.into_output();
    let mut en_pin2 = pins.d9.into_output();
    let mut left_drive = diff_drive::DiffDrive::new(pwm_pin, en_pin1, en_pin2);

The output pins work fine, but the PwmPin ( from embedded HAL ) give me a weird trait error.

error[E0277]: the trait bound `avr_hal_generic::port::Pin<PwmOutput<arduino_hal::simple_pwm::Timer2Pwm>, PD3>: PwmPin` is not satisfied
  --> src/main.rs:48:26
   |
48 |     let mut left_drive = diff_drive::DiffDrive::new(pwm_pin, en_pin1, en_pin2);
   |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `PwmPin` is not implemented for `avr_hal_generic::port::Pin<PwmOutput<arduino_hal::simple_pwm::Timer2Pwm>, PD3>`

This seems to be covered by PwmPinOps<TC>.

I cannot work out why the trait is not covered...

Any hints ?

[Rahix]

I don't think we implement the PwmPin trait from embedded-hal right now. So you'll have to be generic over the PwmPinOps instead, as you noticed. Maybe this works:

use arduino_hal::port::{Pin, PinOps, mode};
use arduino_hal::simple_pwm::PwmPinOps;

#[derive(Default)]
struct Config;

pub struct DiffDrive<TC, E, P1, P2> {
    en: Pin<mode::PwmOutput<TC>, E>,
    p1: Pin<mode::Output, P1>,
    p2: Pin<mode::Output, P2>,
    config: Config,
}

impl<TC, E: PwmPinOps<TC>, P1: PinOps, P2: PinOps> DiffDrive<TC, E, P1, P2> {
    pub fn new(
        en: Pin<mode::PwmOutput<TC>, E>,
        p1: Pin<mode::Output, P1>,
        p2: Pin<mode::Output, P2>,
    ) -> Self {
        let config = Config::default();
        Self { en, p1, p2, config }
    }
}

One important sidenote: The import use arduino_hal::simple_pwm::PwmPinOps; requires the latest version as I just pushed commit 3b8f39f ("mcu: Re-export PwmPinOps through the HALs") to make this work.

[zignig]

Excellent, Thanks @Rahix , that worked a treat. I did actually try doing it with PwmPinOps , but it was missing the pub that you fixed in the release.

Thanks for answering so promptly with a quick fix, much appreciated.

I will continue to build my robot and publish here on github once I have cleaned it up a bit.