Implement the `embedded-hal-async` Traits once stabilized

[jessebraham]

I believe it's still too early to begin work on this, but once a stable release (or at the very least a more stable alpha release) is available we can revisit this topic.

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In embedded-hal-async@0.2.0-alpha.1 the traits to implement are:

• embedded_hal_async::delay::DelayUs
• embedded_hal_async::digital::Wait
• embedded_hal_async::i2c::I2c
• embedded_hal_async::spi::SpiBus
• embedded_hal_async::spi::SpiBusFlush
• embedded_hal_async::spi::SpiBusRead
• embedded_hal_async::spi::SpiBusWrite
• embedded_hal_async::spi::SpiDevice
• embedded_hal_async::spi::SpiDeviceRead
• embedded_hal_async::spi::SpiDeviceWrite
• embedded_hal_async::serial::Write

[bjoernQ]

I did that for another HAL and I agree it's too early since there are a lot of moving parts, still. But once it's (more) stable I'm happy to see this implemented

Commented on the wrong issue 😄

[bjoernQ]

I think we could and should do this in a separate crate which will use esp-hal under the hood.

That way

• we don't "destabilize" the HAL in case of (foreseeable) breaking changes
• we need interrupt handling for the wakers ... I think we would mixup things here if we implement it here
• we can experiment with it without breaking anything in HAL

For I2C and SPI we will need interrupt support which we don't have yet. But probably we could implement delay and wait for digital inputs any time since we have support for it

[bjoernQ]

I tried something here: https://github.com/bjoernQ/esp32c3-async-rs-experiment
Really just only async gpio input but at least it seems that implementing async HAL in a separate crate is possible and makes sense. The code is terrible but it proves what I wanted to check

[jessebraham]

Cool, thanks for sharing!

Should we just add an esp-hal-async package or something to this repo, or how did you want to go about doing this?

[bjoernQ]

Didn't even think about that - probably a good idea. I'm just not sure if we want one Async-HAL with features for each chip or one Async-HAL for each chip (similar to what we have for esp-hal). The later would be more consistent with esp-hal - really not sure what the best way would be. Also interesting what the progress for #57 and #80 is

[MabezDev]

Working on embedded_hal_async::digital::Wait.