NAU88C22-rs

A Rust embedded-hal-async based driver for the Nuvoton NAU88C22 24-bit stereo audio codec.

The NAU88C22 audio codec includes drivers for speaker, headphone, differential and stereo line outputs, along with integrated preamps for stereo differential microphones. Along with having a low ADC SNR of 89dB @ 0dB gain and a DAC SNR of 89dB @ 0dB gain, and it's low price of $1CAD per unit makes it a very flexible and cost effective audio codec for stereo audio applications.

Uses libm to avoid requiring nightly and core_intrinsics.

Data Sheet

docs.rs Link

Codec Clock/PLL Configuration

I've copied the calculations from the manual for initializing the codec's IMCLK and PLL to work with any desired input MCLK frequency and put them in the clock module. These have been tested on my boards to output the correct values for a range of source clocks with a desired 48kHz sampling rate.

// Calculate the codec master clock divisor and PLL for the
// provided input clock frequency and desired sample rate.
let clock = clock::calculate_pll(config.mclk, config.sample_rate).unwrap();
// clock.pll_n, clock.pll_k1, etc..

These can be calculated and directly applied to the codec using the configure_pll convenience method:

codec.configure_pll(ClockConfig{
    // The frequency of the MCLK signal applied to the codec on pin 11.
    //
    // If this is matched closely to your desired sample rate frequency
    // (sample_rate*256) then you won't even need to configure the PLL.
    // 
    // I.e., for 48kHz sample rate you'd, want a clock at or slightly under
    // 12.288MHz (codec can't handle higher without audio quality issues).
    mclk: 2_884_000, // hz

    // Desired sample rate.
    //
    // Note that if you can't exactly match the sample rate on your digital audio
    // output, set this to the actual skewed sample rate to avoid sound glitches.
    sample_rate: 48_000, // hz
}, delay).await?;

Or all at once along with an audio config using codec.initialize(...).

Example

use nau88c22_rs::Nau88c22;

async fn main () {
    // Set up the I2C device based on your HAL.
    let i2c;

    // Initialize the codec using the I2C device.
    let codec = Nau88c22yg::new(i2c);

    // Software reset the codec to known default register values.
    codec.reset().await.unwrap();
}

License

This crate is licensed under the MIT license.