Bidirectional I2S

[relic-se]

New class, audiobusio.I2S, which can be used to both record and playback audio over a unified I2S bus (single pair of bit clock and word select pins).

Notes:

• This functionality currently relies on PIO and is only functional on RP2xxx boards. I am not familiar with the architecture of other boards which implement the audiobusio module: Atmel SAMD, Espressif ESP32, or i.MX RT1020. Support for these boards (if possible) would likely have to come in later updates.
• The interface is mostly synonymous with audiobusio.I2SOut except that data pin direction needs to be specified in keyword, ie: data_out=..., data_in=....
• Keyword arguments are available to specify sample_rate, bits_per_sample, channel_count, etc, but are only necessary if utilizing input. Otherwise, the bus will use the parameters of the sample argument. If the bus is bidirectional and a sample is played that does not match the input parameters, a relevant ValueError will be thrown.
• The audio dma system has been modified to allow bidirectional or input-only operation.
• Testing has been conducted with a Pimoroni Pico Plus 2, an ICS43434 I2S microphone and a PCM5102A I2S DAC.

Comments:

• I worry about delays potentially caused by waiting on the input buffer during audiobusio_i2s_get_buffer.
• I'm calling RUN_BACKGROUND_TASKS when using the bus as an input only while waiting for the incoming buffer. When the bus is operating bidirectionally, it waits with a sample-length sleep loop. There is likely a better solution out there.
• I've created a separate audiobusio.I2SIn that I was testing with initially. I plan on removing this class before marking the PR as ready.

Todo:

• Support mono input with stereo output.
• Fix mismatched buffer sizes.
• (optional) Add record method (or similar) to get current input buffer. Could be useful for monitoring input level.

[relic-se]

I've located a new bug. When using a buffer size on audiomixer.Mixer or an audio effect that is less than that of audiobusio.I2S, the audio distorts significantly.

import board
import audiobusio
import audiomixer

codec = audiobusio.I2S(
    bit_clock=board.GP0,
    word_select=board.GP1,
    data_in=board.GP2,
    data_out=board.GP3,
    sample_rate=22050,
    buffer_size=1024,
)

mixer = audiomixer.Mixer(
    voice_count=1,
    sample_rate=22050,
    buffer_size=512,
)

codec.play(mixer)
mixer.play(codec)

[gamblor21]

Was this the PR you were looking at some help to get past some technical hurdles? I think I may have time to help if you wanted me to poke at this as well. I will have to get some hardware that can do I2S input still.

[relic-se]

Was this the PR you were looking at some help to get past some technical hurdles? I think I may have time to help if you wanted me to poke at this as well. I will have to get some hardware that can do I2S input still.

There have been a couple of changes to audio dma recently. I likely need to revise a lot of this before pushing for a review. I also think the recent changes to garbage collection may improve this feature and was likely why the performance was unacceptable in the first place.

As for compatible hardware, there are a few options:

• I've been using the WM8960 breakout by SparkFun, but the Adafruit Voice Bonnet would be a good option paired with either a Pico to Pi HAT converter or Waveshare RP2040-PiZero.
• The simplest option would be to use an I2S microphone and share the same bus as your DAC.
• I'd like to eventually make a breakout for the TLV320AIC310x, since I think that would be a good candidate and similar to the one on the Fruit Jam.

[ladyada]

hiya just FYI the WM8960 is totally end of line / disco'd - we're making a breakout for the tlv320aic3100 (& maybe friends) and thats what we should probably target long-term :)

[relic-se]

hiya just FYI the WM8960 is totally end of line / disco'd - we're making a breakout for the tlv320aic3100 (& maybe friends) and thats what we should probably target long-term :)

@ladyada I agree. Plus, I find the noise level in the output of that IC not ideal. I'm glad to hear y'all are working with that codec. I'll definitely want to try it out.

As for the rest of the family, have you considered the TLV320AIC3104? It adds stereo to the ADC and balanced line output, but loses the speaker amp. That's the one I'm planning to use in the future for my projects.

Thank you for your input! And I'll take another look at this PR soon with that in mind.