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I have been trying to implement spi on STM32F407 discovery mode in DMA mode. I got the data, but the problem is that, I have 112 bits of data via Pulse Position Modulation, and the frequency of data is 1MHz. Since this info signal is arbitrary, I've configured my board as a slave (although there is no real master) and I make SCK from board itself via PWM. The thing is, that I am receiving data, but I get the whole 112 bits in 42 pulses. I am not sure of how the SPI is triggered by the SCK, since the durrations do not match. There is configuration of my SPI:

static void MX_SPI1_Init(void)
{
/* SPI1 parameter configuration*/
hspi1.Instance = SPI1;
hspi1.Init.Mode = SPI_MODE_SLAVE;
hspi1.Init.Direction = SPI_DIRECTION_2LINES;
hspi1.Init.DataSize = SPI_DATASIZE_8BIT;
hspi1.Init.CLKPolarity = SPI_POLARITY_HIGH;
hspi1.Init.CLKPhase = SPI_PHASE_1EDGE;
hspi1.Init.NSS = SPI_NSS_HARD_INPUT;
hspi1.Init.FirstBit = SPI_FIRSTBIT_MSB;
hspi1.Init.BaudRatePrescaler=SPI_BAUDRATEPRESCALER_4;
hspi1.Init.TIMode = SPI_TIMODE_DISABLE;
hspi1.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
hspi1.Init.CRCPolynomial = 7;
if (HAL_SPI_Init(&hspi1) != HAL_OK)
{
_Error_Handler(__FILE__, __LINE__);
}}

My msp.c file

void HAL_SPI_MspInit(SPI_HandleTypeDef* hspi)
{
GPIO_InitTypeDef GPIO_InitStruct;
if(hspi->Instance==SPI1)
{
/* USER CODE BEGIN SPI1_MspInit 0 */
    __HAL_RCC_GPIOA_CLK_ENABLE();
    __HAL_RCC_GPIOB_CLK_ENABLE();
/* USER CODE END SPI1_MspInit 0 */
/* Peripheral clock enable */
__HAL_RCC_SPI1_CLK_ENABLE();

/**SPI1 GPIO Configuration    
PA4     ------> SPI1_NSS
PA6     ------> SPI1_MISO
PA7     ------> SPI1_MOSI
PB3     ------> SPI1_SCK 
*/
GPIO_InitStruct.Pin = GPIO_PIN_4|GPIO_PIN_6|GPIO_PIN_7;
GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
GPIO_InitStruct.Alternate = GPIO_AF5_SPI1;
HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

GPIO_InitStruct.Pin = GPIO_PIN_3;
GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
GPIO_InitStruct.Pull = GPIO_NOPULL;
GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
GPIO_InitStruct.Alternate = GPIO_AF5_SPI1;
HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

/* SPI1 DMA Init */
/* SPI1_RX Init */
hdma_spi1_rx.Instance = DMA2_Stream0;
hdma_spi1_rx.Init.Channel = DMA_CHANNEL_3;
hdma_spi1_rx.Init.Direction = DMA_PERIPH_TO_MEMORY;
hdma_spi1_rx.Init.PeriphInc = DMA_PINC_DISABLE;
hdma_spi1_rx.Init.MemInc = DMA_MINC_ENABLE;
hdma_spi1_rx.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
hdma_spi1_rx.Init.MemDataAlignment = DMA_MDATAALIGN_BYTE;
hdma_spi1_rx.Init.Mode = DMA_NORMAL;
hdma_spi1_rx.Init.Priority = DMA_PRIORITY_LOW;
hdma_spi1_rx.Init.FIFOMode = DMA_FIFOMODE_DISABLE;
if (HAL_DMA_Init(&hdma_spi1_rx) != HAL_OK)
{
  _Error_Handler(__FILE__, __LINE__);
}

__HAL_LINKDMA(hspi,hdmarx,hdma_spi1_rx);

/* SPI1 interrupt Init */
HAL_NVIC_SetPriority(SPI1_IRQn, 0, 0);
HAL_NVIC_EnableIRQ(SPI1_IRQn);
/* USER CODE BEGIN SPI1_MspInit 1 */
/* USER CODE END SPI1_MspInit 1 */
}}

I start SPI via:

HAL_SPI_Receive_DMA(&hspi1, data, 14); //data is array uint8_t
HAL_GPIO_WritePin(GPIOA, GPIO_PIN_5, GPIO_PIN_RESET); //NSS out which is shortened with real NSS of Slave
HAL_TIM_PWM_Start(&htim3, TIM_CHANNEL_1); /clock

After I got the data I use this in SPI handler:

HAL_GPIO_WritePin(GPIOA, GPIO_PIN_5, GPIO_PIN_SET);
HAL_TIM_PWM_Stop(&htim3, TIM_CHANNEL_1);

In memory I got all of the 112 (14 bytes) Data

And there is the oscilogram Oscilogram

Any ideas? I have used CubeMX as a base of my code

  • 1
    I'm not sure this question can be answered without understanding the whole application, including schematics (in which case it should be asked on the electronics site instead of here). One question though... why does the signal look like complete crap on your scope picture? Did you not ground the probe? Otherwise it would seem you are suffering from some heavy EMI noise. – Lundin Nov 10 '17 at 12:07
  • I am currently simulating ADS-B packages via arbitrary function generator, and yeah, the ground cable came off of the ground pin. The goal is detecting 4 impulses which indicates that the package is incoming and I sync via it to decode the data. Since I have low resources, I am trying to use as little CPU as possible, because I will need to transmit the data elsewhere. – Almantas Karosevičius Nov 10 '17 at 12:30

0 Answers0