Yote - Year of the Ear

Experiments with the nrf5340 Audio Dk, CS47L63 DSP chip and Yote experimental hearing aid. For Rust firmware, open the firmware folder instead of working from this folder

Prerequisites

cargo install probe-rs --features="cli"

If probe-rs does not work then a known working version can be found here: https://github.com/probe-rs/probe-rs.git#ff2370fb

To run

NOTE on naming: All the examples prefixed with "yote" are for the custom built hearing aid device. Everything else is for the nRF5340 Audio-dk

IMPORTANT: be sure to set the appropriate runner in .cargo/config.toml

cargo run --bin blinky --release

Troubleshooting

You may get an "Arm specific error at runtime and the most likely cause is that you ran probe-run with the --erase-all flag set. Check the notes in .cargo/config.toml

Here are some commands you may find useful when working with the nrf5340 audio dk. You will need to install the nrfjprog command line tools from Nordic beforehand.

nrfjprog -i
nrfjprog --eraseall --snr 1050175639 (locks up)
nrfjprog --recover --coprocessor CP_APPLICATION --snr 1050175639
nrfjprog --recover --snr 1050175639 (same as application above)
nrfjprog --recover --coprocessor CP_NETWORK --snr 1050175639 (locks up)

Here is some code that you can use to flash the device without probe-run:

#! /usr/bin/env bash

cargo objcopy --release -- -O ihex test.hex
nrfjprog -f NRF53 --erasepage 0x00000000-0x00100000
nrfjprog -f NRF53 --program test.hex --debugreset
rm test.hex

How it works

This demo uses the mcu to generate a tone and plays it into the cs47l63 dsp chip. Before it can do that it has to configure the dsp chip correctly by writing to various registers over spi. There are multiple tasks running simultaneously so we need a mechanism to share the spi bus between them.

The demo runs three main tasks simultaneously:

1. Handle interrupts from the DSP chip which indicates that long running tasks on the DSP have been completed
2. Handle button presses to control playback and volume
3. Generate a waveform in real time and push the data to the DSP chip over the I2S sound bus

Project structure

The cs47l63 cargo library is responsible for booting up the cs47l63 chip correctly and providing a bunch of register address and constants to be used by the application. The hw_dsp (hardware digital signal processing) constrains a collection of helper functions that make calls to the cs47l63 driver to configure it. The main.rs application should use dsp module to exclusively communicate with the cs47l63 even though, in theory, it could communicate directly with it through the shared_bus module. Right now there is some code duplication because of some power saving experiments where we need to drop the spi bus after every use. The duplicated code should be consolidated as soon as an acceptable abstraction has been designed.

Chapro compilation

CC=arm-none-eabi-gcc AR=arm-none-eabi-ar CFLAGS = -W -Wall -Os -mthumb -ffunction-sections -fdata-sections -mcpu=cortex-m33 -DBR_ARMEL_CORTEXM_GCC -I$(INCDIR) -Wno-unused-local-typedef -fPIC -mfpu=fpv5-sp-d16 -mfloat-abi=hard

Notes on Power Consumption

Here are some of the things that seem to affect power consumption:

Logging: No effect unless a debugger is attached - then huge effect Core clock 64Mhz -> 128Mhz and Flash Cache enabled - 200uA consumption Setting all peripheral pins to Input Low on startup - no effect, they seem to already default to their lowest power setting anyway