Electronic – DMA completion interrupt not working for slave STM32 SPI

dmaspistm32

I am using stm32f103 to transmit some data over SPI while stm32 acts as slave. I need to use DMA for sending data to the SPI but the corresponding interrupt handler is never called.

The initialization code comes in the following:

DMA_InitTypeDef DMA_InitStructure;
/* DMA configuration */
DMA_DeInit(SPI_SLAVE_DMA);
DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t) SPI_SLAVE_DR_Adress;
DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t) SPI_Buffer;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
DMA_InitStructure.DMA_BufferSize = SPI_BufferSize;
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
DMA_InitStructure.DMA_Priority = DMA_Priority_VeryHigh;
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
DMA_Init(SPI_SLAVE_DMA, &DMA_InitStructure);
/* Enable DMA Transfer Complete interrupt */
DMA_ITConfig(SPI_SLAVE_DMA, DMA_IT_TC, ENABLE);
/* Enable DMA */
DMA_Cmd(SPI_SLAVE_DMA, ENABLE);

/* SPI_SLAVE configuration */
SPI_InitTypeDef SPI_InitStructure;
SPI_InitStructure.SPI_Direction = SPI_Direction_1Line_Tx;
SPI_InitStructure.SPI_Mode = SPI_Mode_Slave;
SPI_InitStructure.SPI_DataSize = SPI_DataSize_16b;
SPI_InitStructure.SPI_CPOL = SPI_CPOL_Low;
SPI_InitStructure.SPI_CPHA = SPI_CPHA_2Edge;
SPI_InitStructure.SPI_NSS = SPI_NSS_Hard;
SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_2;
SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;
SPI_InitStructure.SPI_CRCPolynomial = 7;
SPI_Init(SPI_SLAVE, &SPI_InitStructure);

/* Enable SPI_SLAVE Tx request */
SPI_I2S_DMACmd(SPI_SLAVE, SPI_I2S_DMAReq_Tx, ENABLE);
/* Enable SPI_SLAVE */
SPI_Cmd(SPI_SLAVE, ENABLE);

When I use SPI interrupt handler, my system works. But using the code written above, interrupt handler of SPI_SLAVE_DMA channel is never called.

Best Answer

I found the solution. In reference manual of STM32f103xx there is a table (No. 78) clarifying that which DMA channel can be used for which peripheral. According to that table, I had to use DMA1 channel3, while I was using channel6 instead.

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Electronic – Full duplex slave SPI, DMA and interrupts on STM32F103

Below a code that works for me. DMA channel assignment is critical. DMA1 channel 4 for SPI2 RX request and DMA1 channel 5 for SPI2 TX request. See here, page 147:

http://www.st.com/web/en/resource/technical/document/reference_manual/CD00246267.pdf

uint16_t SPIReceivedValue[2];
uint16_t SPITransmittedValue[2] = {0xFF00,0x00FF};

void SPI_Slave_and_DMA_Configuration(void)
{
    SPI_InitTypeDef SPI_InitStructure; //Variable used to setup the SPI
    DMA_InitTypeDef DMA_InitStructure; //Variable used to setup the DMA


    //--Enable the SPI2 periph
    RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI2, ENABLE);

    // Reset SPI Interface
    SPI_I2S_DeInit(SPI2);

    //== SPI2 configuration
    SPI_StructInit(&SPI_InitStructure);
    SPI_InitStructure.SPI_Direction = SPI_Direction_2Lines_FullDuplex;
    SPI_InitStructure.SPI_Mode = SPI_Mode_Slave;
    SPI_InitStructure.SPI_DataSize = SPI_DataSize_16b;
    SPI_InitStructure.SPI_CPOL = SPI_CPOL_Low;
    SPI_InitStructure.SPI_CPHA = SPI_CPHA_1Edge;
    SPI_InitStructure.SPI_NSS = SPI_NSS_Hard;
    SPI_InitStructure.SPI_FirstBit = SPI_FirstBit_MSB;
    SPI_InitStructure.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_2;
    SPI_InitStructure.SPI_CRCPolynomial = 7;
    SPI_Init(SPI2, &SPI_InitStructure);


    //--Enable DMA1 clock--
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE);

    //==Configure DMA1 - Channel4== (SPI -> memory)
    DMA_DeInit(DMA1_Channel4); //Set DMA registers to default values
    DMA_StructInit(&DMA_InitStructure);
    DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&SPI2->DR; //Address of peripheral the DMA must map to
    DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)&SPIReceivedValue[0]; //Variable to which received data will be stored
    DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralSRC;
    DMA_InitStructure.DMA_BufferSize = 2; //Buffer size
    DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
    DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
    DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
    DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
    DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
    DMA_InitStructure.DMA_Priority = DMA_Priority_High;
    DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
    DMA_Init(DMA1_Channel4, &DMA_InitStructure); //Initialise the DMA
    DMA_Cmd(DMA1_Channel4, ENABLE); //Enable the DMA1 - Channel4         

    //==Configure DMA1 - Channel5== (memory -> SPI)
    DMA_DeInit(DMA1_Channel5); //Set DMA registers to default values
    DMA_StructInit(&DMA_InitStructure);
    DMA_InitStructure.DMA_PeripheralBaseAddr = (uint32_t)&SPI2->DR; //Address of peripheral the DMA must map to
    DMA_InitStructure.DMA_MemoryBaseAddr = (uint32_t)&SPITransmittedValue[0]; //Variable from which data will be transmitted
    DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;
    DMA_InitStructure.DMA_BufferSize = 2; //Buffer size
    DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
    DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
    DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
    DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
    DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
    DMA_InitStructure.DMA_Priority = DMA_Priority_High;
    DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;
    DMA_Init(DMA1_Channel5, &DMA_InitStructure); //Initialise the DMA
    DMA_Cmd(DMA1_Channel5, ENABLE); //Enable the DMA1 - Channel5         

    // Enable SPI2
    SPI_Cmd(SPI2, ENABLE);

    // Enable the SPI2 RX & TX DMA requests
    SPI_I2S_DMACmd(SPI2, SPI_I2S_DMAReq_Rx | SPI_I2S_DMAReq_Tx, ENABLE);
}

Electronic – STM32 SPI w/ DMA “BUSY” flag set

What exactly is throttling the SPI transfers? If you're using DMA directly (rather than triggered by a timer or something else), then as soon as the SPI is free, the DMA peripheral would start another transfer. As a result, being busy all the time would be expected.

According to the manual for the STM32F1xx series, section 25.3.7 (other series should have similar behavior):

When communication is not continuous, the BSY flag is low between each communication.

When communication is continuous:

● in master mode, the BSY flag is kept high during all the transfers

Best Answer

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Electronic – Full duplex slave SPI, DMA and interrupts on STM32F103

Electronic – STM32 SPI w/ DMA “BUSY” flag set

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