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I am using STM32F4 discovery board and I am attempting to get SPI loopback with DMA.

I have successfully got an "SPI-only" loopback running, but now I want use DMA in addition with the SPI, here are the functions that I am using:

Initialisation of SPI

void init_SPI1(void){    
  NVIC_InitTypeDef NVIC_InitStructure;
  GPIO_InitTypeDef GPIO_InitStruct;
  SPI_InitTypeDef SPI_InitStruct ;

  RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);

  GPIO_InitStruct.GPIO_Pin = GPIO_Pin_7 | GPIO_Pin_6 | GPIO_Pin_5|GPIO_Pin_4;
  GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF;
  GPIO_InitStruct.GPIO_OType = GPIO_OType_PP;
  GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStruct.GPIO_PuPd = GPIO_PuPd_NOPULL;
  GPIO_Init(GPIOA, &GPIO_InitStruct);
  // connect SPI1 pins to SPI alternate function

  GPIO_PinAFConfig(GPIOA, GPIO_PinSource4, GPIO_AF_SPI1);
  GPIO_PinAFConfig(GPIOA, GPIO_PinSource5, GPIO_AF_SPI1);
  GPIO_PinAFConfig(GPIOA, GPIO_PinSource6, GPIO_AF_SPI1);
  GPIO_PinAFConfig(GPIOA, GPIO_PinSource7, GPIO_AF_SPI1);

  //Set chip select high 
  GPIOA->BSRRL |= GPIO_Pin_4; // set PA4 high

  // enable SPI1 peripheral clock
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_SPI1, ENABLE);
  /* configure SPI1 in Mode 0 
   * CPOL = 0 --> clock is low when idle
   * CPHA = 0 --> data is sampled at the first edge*/
  SPI_StructInit(&SPI_InitStruct); // set default settings 
  SPI_InitStruct.SPI_Direction = SPI_Direction_2Lines_FullDuplex; // set to full duplex mode, seperate MOSI and MISO lines
  SPI_InitStruct.SPI_Mode = SPI_Mode_Master;     // transmit in master mode, NSS pin has to be always high
  SPI_InitStruct.SPI_DataSize = SPI_DataSize_8b; // one packet of data is 8 bits wide
  SPI_InitStruct.SPI_CPOL = SPI_CPOL_Low;        // clock is low when idle
  SPI_InitStruct.SPI_CPHA = SPI_CPHA_1Edge;      // data sampled at first edge
  SPI_InitStruct.SPI_NSS = SPI_NSS_Soft ; // set the NSS management to internal and pull internal NSS high
  SPI_InitStruct.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_4; // SPI frequency is APB2 frequency / 4
  SPI_InitStruct.SPI_FirstBit = SPI_FirstBit_MSB;// data is transmitted MSB first
  SPI_Init(SPI1, &SPI_InitStruct); 

  NVIC_InitStructure.NVIC_IRQChannel = SPI1_IRQn;
  NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
  NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;
  NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
  NVIC_Init(&NVIC_InitStructure);  

  return;
}        

Configuration of DMA:

void DMA_Config()
{  
DMA_InitTypeDef DMA_InitStructure;   
NVIC_InitTypeDef NVIC_InitStructure;

RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2, ENABLE);

DMA_ClearFlag(DMA2_Stream2,        DMA_FLAG_FEIF2|DMA_FLAG_DMEIF2|DMA_FLAG_TEIF2|DMA_FLAG_HTIF2|DMA_FLAG_TCIF2);
DMA_Cmd(DMA2_Stream2, DISABLE);
while (DMA2_Stream2->CR & DMA_SxCR_EN);
DMA_DeInit(DMA2_Stream5);
DMA_StructInit(&DMA_InitStructure);

DMA_InitStructure.DMA_Channel = DMA_Channel_3;
DMA_InitStructure.DMA_PeripheralBaseAddr  = (uint32_t) &(SPI1->DR);
DMA_InitStructure.DMA_Memory0BaseAddr  = (uint32_t) &spiTxBuff;
DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToPeripheral;
DMA_InitStructure.DMA_BufferSize  = SPI_TX_MAX;
DMA_InitStructure.DMA_PeripheralInc  = DMA_PeripheralInc_Disable;
DMA_InitStructure.DMA_MemoryInc  = DMA_MemoryInc_Enable;
DMA_InitStructure.DMA_PeripheralDataSize  = DMA_PeripheralDataSize_Byte;
DMA_InitStructure.DMA_MemoryDataSize  = DMA_MemoryDataSize_Byte;
DMA_InitStructure.DMA_Mode  = DMA_Mode_Normal;
DMA_InitStructure.DMA_Priority  = DMA_Priority_High;
DMA_InitStructure.DMA_FIFOMode  = DMA_FIFOMode_Disable;

DMA_Init(DMA2_Stream5, &DMA_InitStructure); 

/**
configuration of the interrupts of DMA
******************************************************/
DMA_ITConfig(DMA2_Stream5, DMA_IT_TC, ENABLE);
NVIC_InitStructure.NVIC_IRQChannel = DMA1_Stream5_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 2;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);  
return;
}

SPI Write function:

void SPI1_Write(uint8_t *txBuff,int length,tSPI_Callback fct)
{
 DMA2_Stream5->M0AR = (uint32_t) &spiTxBuff;
 DMA_Cmd(DMA2_Stream5, ENABLE);
 SPI_I2S_DMACmd(SPI1, SPI_I2S_DMAReq_Tx, ENABLE);
 SPI_Cmd(SPI1, ENABLE);
}

The data received are written in the Rx Buffer using the SPI interrupt handler.

void SPI1_IRQHandler()
{
 spiRxBuff[spiRxCount] = SPI_I2S_ReceiveData(SPI1);
 spiRxCount++;
}

I am calling these functions in main() as follows:

main.c:

DMA_Config();
init_SPI1();
SPI1_Write(spiTxBuff,SPI_TX_MAX,(void*)0); 

Using a debugger I found that, in the DMA high interrupt status register, TCIF5 (Transfer Complete Flag) and HTIF5 (Half Transfer complete Flag) are set to 1, which means that the transfer is done successfully, in my opinion, however I didn't get any data in the SPI Rx Buffer. The second strange thing is that neither DMA Interrupt nor SPI Interrupt is triggered. Could you please help me figure out what is wrong in my code?

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  • \$\begingroup\$ What about the Tx, is it working? having you tried putting a breakpoint in the SPI interrupt handler, to check if it's ever triggered? \$\endgroup\$ – Florent May 9 '16 at 11:37
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There is some mistakes that i corrected and get the expected result:

1) SPI Rx interrupt is not configured,this line SPI_I2S_ITConfig(SPI1,SPI_I2S_IT_RXNE,ENABLE) was missed

2) In the function DMA_Config DMA1 interrupts are enabled instead of DMA2, this line NVIC_InitStructure.NVIC_IRQChannel = DMA1_Stream5_IRQn;

This is the working solution

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