Use DMA Transfer API in I2S module

[kalkyl]

I changed the I2S module to use a DMA Transfer API for TX and RX operations.
I also added support for full duplex transfers and the demos were updated according to the new API.

"Controller mode" demo (TX):
https://github.com/kalkyl/nrf-hal/blob/i2s-dma/examples/i2s-controller-demo/src/main.rs

"Peripheral mode" demo (RX):
https://github.com/kalkyl/nrf-hal/blob/i2s-dma/examples/i2s-peripheral-demo/src/main.rs

[jonas-schievink]

Thanks!

I think Pin might not be the right thing to use for DMA APIs (see rust-embedded/embedonomicon#64). The embedded-dma crate provides traits for DMA APIs though, I wonder if we should just use those.

[kalkyl]

Thanks!

I think Pin might not be the right thing to use for DMA APIs (see rust-embedded/embedonomicon#64). The embedded-dma crate provides traits for DMA APIs though, I wonder if we should just use those.

Ahh i see... I can't really figure out how to implement them for this at the moment, i guess i haven't fully understood how they're supposted to be used... Any hints?

[jonas-schievink]

I've also never used them so far, unfortunately.

[kalkyl]

I’ll do my homework ;)

[kalkyl]

Ok i have a working implementation using the embedded_dma traits. The only problem is embedded_dma doesn't implement Word for signed integer types, so we'd need upstream support for that to make it usable.
It works with my local patched version, so i submitted a PR to embedded-dma adding them in:
rust-embedded/embedded-dma#3

[eldruin]

FYI, I just published embedded-dma 0.1.1

[jonas-schievink]

Looks good, thanks!