WM8940 audio codec library for STM32

Useful links:

• Product page: https://www.cirrus.com/products/wm8940/
• Datasheet: https://statics.cirrus.com/pubs/proDatasheet/WM8940_v4.4.pdf

How to use

Write your implementation to write/read register from the device. For example:

// --- main.c ---

void MyI2C_Write(I2C_HandleTypeDef* i2c_handle, uint8_t i2c_address, uint8_t register, uint16_t value)
{
    // TODO
}

uint16_t MyI2C_Read(I2C_HandleTypeDef* i2c_handle, uint8_t i2c_address, uint8_t register)
{
    // TODO
}

// --- main.h ---

void MyI2C_Write(I2C_HandleTypeDef* i2c_handle, uint8_t i2c_address, uint8_t register, uint16_t value);
uint16_t MyI2C_Read(I2C_HandleTypeDef* i2c_handle, uint8_t i2c_address, uint8_t register);

Edit the wm8940.h to call your implementation

// --- wm8940.h ---

#include "main.h"    // The location of the function prototype for the implementation

#define WM8940_REG_WRITE(handle, reg, val) MyI2C_Write(handle, WM8940_I2C_ADDRESS, reg, val)
#define WM8940_REG_READ(handle, reg) MyI2C_Read(handle, WM8940_I2C_ADDRESS, reg)

Now you can initialize the audio codec, configure the Digital Audio Interface to transmit/receive audio data, and follow the Audio Signal Path from the datasheet.

// --- main.c ---

#include "wm8940.h"

WM8940_t wm8940;

int main(void)
{
    // ...

    wm8940.comm_handle = &hi2c1;
    WM8940_Init(&wm8940);

    // STM32 as I2S Master
    WM8940_Set_Clock(&wm8940, 0, WM8940_BCLKDIV_1, WM8940_MCLKDIV_1, WM8940_CLKSEL_MCLK);
    WM8940_Set_AudioInterfaceFormat(&wm8940, WM8940_AUDIO_IFACE_FMT_I2S, WM8940_AUDIO_IFACE_WL_16BITS);
    WM8940_Set_SampleRate(&wm8940, WM8940_SAMPLERATE_8KHZ);

    // Audio bypass from MICN to Speaker (BTL) and Mono
    WM8940_Set_PGA_Input(&wm8940, WM8940_INPUT_MICN);
    WM8940_Set_PGA_Mute(&wm8940, 1);
    WM8940_Set_PGA_Enable(&wm8940, 1);
    WM8940_Set_Boost_Enable(&wm8940, 1);
    WM8940_Set_MicBias_Enable(&wm8940, 1);
    WM8940_Set_Speaker_Source(&wm8940, WM8940_OUTPUT_FROM_BYPASS);
    WM8940_Set_Speaker_Mute(&wm8940, 0);
    WM8940_Set_Mono_Source(&wm8940, WM8940_OUTPUT_FROM_BYPASS);
    WM8940_Set_Mono_Mute(&wm8940, 0);
    WM8940_Set_Output_Enable(&wm8940, WM8940_OUTPUT_SPK | WM8940_OUTPUT_MONO);

    // ...
}

Implemented (based on device description):

• Input signal path
  • Microphone inputs
  • Input PGA volume control
  • Auxiliary input
  • Input boost
  • Microphone biasing
• Analogue to Digital Converter (ADC)
  • High pass filter
  • Notch filter
  • Digital ADC volume control
• Input limiter/Automatic Level Control (ALC)
  • Operation mode (Normal/Limiter)
  • Attack and decay times
  • Minimum and maximum gain
  • Hold time and ALC level
  • Noise gate
  • ALC zero cross
• Output signal path
  • Hi-Fi DAC volume control
  • Hi-Fi Digital to Analogue Converter (DAC)
  • Automute
  • DAC output limiter
  • Volume boost
• Analogue outputs
  • SPKOUTP/SPKOUTN outputs
  • Zero cross timeout
  • Enabling the outputs
  • Unused analogue inputs/outputs (VREF to analogue output resistance/VROI)
• Output switch
  • Thermal shutdown
• Digital audio interfaces
  • Set audio format
  • Set word length
  • Set frame clock and BCLK polarity
  • Set LOUTR
  • (ADC & DAC) data L&R swap
  • Clock generation control
• Audio sample rates
• Master clock and Phase Locked Loop (PLL)
  • Enable PLL
  • Set PLL power
  • Set PLL frequency
• Companding
  • (ADC & DAC) Loopback
  • (ADC & DAC) Companding
  • Enable 8-bit word length
• General Purpose Input/Output
• Control interface
  • Selection of control mode
  • Auto-incremental write setting
  • Readback
• Resetting the chip
• Power management
  • VMID control
  • BIASEN control
• POP minimisation
  • Power on Bias control (configured on init)
  • VMID soft start (configured on init)
  • Fast VMID discharge