Migrating Async ADC abstraction from 0.23.1 to 1.0.0-beta.0

[renkenono]

Hello,

First, thanks for the amazing work done on esp-hal.

For the current project I am working on, I implemented a quick abstraction to facilitate implementing ADC value conversion per-device in which a device is defined by a type, to make use of Rust's type safety.

// esp-hal = "0.23.1"
use core::marker::PhantomData;
use esp_hal::analog::adc::{Adc, AdcCalScheme, AdcChannel, AdcPin, RegisterAccess};
use crate::driver::sensor::{Metering, Sensor};

trait Converter {
    /// Converts the raw ADC value to a valid metering.
    fn raw_to_metering(raw_value: u16) -> Metering;
}

pub struct AdcSensor<'d, ADCI, PIN, CS, MC> {
    adc: Adc<'d, ADCI>,
    pin: AdcPin<PIN, ADCI, CS>,
    _phantom: PhantomData<MC>,
}

impl<'d, ADCI, PIN, CS, MC> AdcSensor<'d, ADCI, PIN, CS, MC> {
    pub fn new(adc: Adc<'d, ADCI>, pin: AdcPin<PIN, ADCI, CS>) -> Self {
        let _phantom = PhantomData::<MC> {};
        Self { adc, pin, _phantom }
    }
}

impl<'d, ADCI, PIN, CS, MC> Sensor for AdcSensor<'d, ADCI, PIN, CS, MC>
where
    ADCI: RegisterAccess + 'd,
    PIN: AdcChannel,
    CS: AdcCalScheme<ADCI>,
    MC: Converter,
{
    async fn measure(&mut self) -> Metering {
        let raw_value = self
            .adc
            .read_oneshot(&mut self.pin)
            .expect("failed to read metering");

        MC::raw_to_metering(raw_value)
    }
}

However, when upgrading to esp-hal 1.0.0-beta.0, the compiler reported the following error.

error[E0277]: the trait bound `ADCI: esp_hal::analog::adc::implementation::asynch::AsyncAccess` is not satisfied
   --> src/sensor/adc.rs:39:34
    |
39  |         let raw_value = self.adc.read_oneshot(&mut self.pin).await;
    |                                  ^^^^^^^^^^^^ the trait `esp_hal::analog::adc::implementation::asynch::AsyncAccess` is not implemented for `ADCI`
    |
note: required by a bound in `esp_hal::analog::adc::Adc::<'d, ADCI, Async>::read_oneshot`
   --> /home/renken/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/esp-hal-1.0.0-beta.0/src/analog/adc/riscv.rs:666:15
    |
664 |     pub async fn read_oneshot<PIN, CS>(&mut self, pin: &mut super::AdcPin<PIN, ADCI, CS>) -> u16
    |                  ------------ required by a bound in this associated function
665 |     where
666 |         ADCI: asynch::AsyncAccess,
    |               ^^^^^^^^^^^^^^^^^^^ required by this bound in `Adc::<'d, ADCI, Async>::read_oneshot`
help: consider further restricting type parameter `ADCI` with trait `AsyncAccess`
    |
33  |     ADCI: RegisterAccess + 'd + esp_hal::analog::adc::implementation::asynch::AsyncAccess,

The printed suggestion points to a rather private trait, esp_hal::analog::adc::implementation::asynch::AsyncAccess. I navigated the source code a bit and I cannot seem to find it exposed in any way, be it directly or indirectly. Perhaps I'm missing something? Or could it be that this abstraction cannot be achieved with the current state of 1.0.0-beta.0?

[MabezDev]

We have a migration guide for all our esp-hal releases: https://github.com/esp-rs/esp-hal/releases/tag/esp-hal-v1.0.0-beta.0 there is a section there about ADC. Essentially we made it so ADC can be initialized in blocking or async mode, you just need to add a Blocking parameter in your driver definition :).

[MabezDev]

Which chip are you targeting? Only the RISCV chips have async ADC support at the moment: #1643

[renkenono]

esp32c6 which should be supported. I also tested my previous implementation, based on 0.23.1, against it and it works.

[MabezDev]

Ah, so the esp32c6 is supported, but only in the main branch of esp-hal. There are a few breaking changes in main, but hopefully this will help: https://github.com/esp-rs/esp-hal/blob/main/esp-hal/MIGRATING-1.0.0-beta.0.md.

[renkenono]

Thanks, I will give it a try as soon as possible.

Closing this discussion as this should be the answer.

[renkenono]

@MabezDev for reference, I opened #3443 in response to this because I believe the fix should be exposing asynch module where applicable. Thanks again for your help!