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STM32F4 - I2S sending & receiving

Question asked by rohrauer.manuel on May 23, 2013
Latest reply on May 23, 2013 by waclawek.jan
Hi togehter,

I've some questions about the I2S interface of the STM32F405 microcontroller. I hope someone could help me I'm in a bit of a crisis here now.

First to my hardware setup:
I've the microcontroller, an audiocodec, a microphjone and a speaker. The microcontroller is connected to the codec via I2S. The speaker and the microphone is connected to the codec.
The codec is working fine; in fact sending data to the speaker is already working.

My Problem is now, I'm not able to receive any data from the microphone. I checked the input data (Pin I2S3ext_SD) with an oscilloscope. On the pin data is present so the codec works fine.
If I configure the I2S in receive mode, I always read zeros, no matter what data is on the I2S3ext_SD

I am also not sure whether I use the FullDuplexConfig right. What do I have to set in I2S_InitStructure.I2S_Mode D) if I use FullDuplex? I only get receiving Interrupts if I set it to MasterRx. Is that right?

Now to my code:
GPIO configuration:
GPIO_InitTypeDef GPIO_InitStructure;
// Enable peripheral clocks
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA | RCC_AHB1Periph_GPIOC, ENABLE);  // TODO: fix, enable alternate function clock
RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI3, ENABLE);
/* configure alternative functions */
GPIO_PinAFConfig(GPIOA, GPIO_PinSource15, GPIO_AF_SPI3);  // I2S3_WS
GPIO_PinAFConfig(GPIOC, GPIO_PinSource7,  GPIO_AF_SPI3);  // I2S3_MCK
GPIO_PinAFConfig(GPIOC, GPIO_PinSource10, GPIO_AF_SPI3);  // I2S3_CK
GPIO_PinAFConfig(GPIOC, GPIO_PinSource11, GPIO_AF_SPI3);  // I2S3_ext_SD
GPIO_PinAFConfig(GPIOC, GPIO_PinSource12, GPIO_AF_SPI3);  // I2S3_SD
// Configure pins as alternate function
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF; // TODO: fix
GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_15;
GPIO_Init(GPIOA, &GPIO_InitStructure);
GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7 | GPIO_Pin_10 | GPIO_Pin_11 | GPIO_Pin_12;
GPIO_Init(GPIOC, &GPIO_InitStructure);

Interrupt: configuration:
NVIC_InitTypeDef NVIC_InitStructure;
NVIC_InitStructure.NVIC_IRQChannel = SPI3_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

I2S3 configuration:
// I2S3 peripheral configuration
SPI_I2S_DeInit(SPI3); // ERRATA: deinitialize i2s3 aka. spi3
I2S_InitStructure.I2S_Standard    = I2S_Standard_Phillips;
I2S_InitStructure.I2S_DataFormat  = I2S_DataFormat_16b; // 16bextended
I2S_InitStructure.I2S_MCLKOutput  = I2S_MCLKOutput_Enable;
I2S_InitStructure.I2S_AudioFreq   = I2S_AudioFreq_8k;
I2S_InitStructure.I2S_CPOL        = I2S_CPOL_Low;
I2S_InitStructure.I2S_Mode        = I2S_Mode_MasterRx;
I2S_Init(SPI3, &I2S_InitStructure);
I2S_FullDuplexConfig(I2S3ext, &I2S_InitStructure);
/* Enable the I2S3 TxE interrupt */
/* Enable the Rx buffer not empty interrupt */
/* Enable the I2S3 */

IRQ Handler:
extern "C" void I2S3_IRQHANDLER(void) { 
  static uint32_t i = 2;
  static uint16_t div = 1;
  // Sending data
  if(SPI_GetITStatus(SPI3, SPI_I2S_IT_TXE) != RESET) {
    if(i <  BUFFER_SIZE) {
      if(i % 2) {
        SPI_I2S_SendData(SPI3,0x0000);  // no right channel cause speaker is mono
      } else {
        // Send square wave
        if((i/8) % 2) {         
          SPI_I2S_SendData(SPI3, 0x7FFF);
        } else {
          SPI_I2S_SendData(SPI3, 0x0000);
      } else {
        SPI_I2S_ITConfig(SPI3, SPI_I2S_IT_TXE, DISABLE);
        i = 2

  // Receiving data
    } else if(SPI_GetITStatus(SPI3, SPI_I2S_IT_RXNE) == SET) {
      static uint16_t bufferSize = 0;
      RAM_Buf[bufferSize++] = SPI3->DR;//SPI_I2S_ReceiveData(SPI3);
      if(bufferSize >= BUFFER_SIZE) {

So this is my code so far. If I debug and check the data of the RAM_Buf in the receiving part of the ISR, the whole array is zero.
I'm relatively new to the STM microcontrollers, so it' probably just a little mistakte you guys can find shortly. Hope you can help me.

Thanks & best regards,