DMA-SPI triggered by Timer STM32G4

[JordiM]

Hello,

I have an STM32G474VEH6 and we have the main function running a code at 20kHz that takes almost all the period to be executed. We also use ADC and PWM synchronised to convert at the period start. Now we also have to read a 64bit SPI slave in master "read only" mode. As far as I know, I need to generate a dummy TX to start the transmission.

The SPI slave has a transmission has a minimum timeout after every transmission of 13.5us and the maximum clock frequency is 5MHz.

Since we want to increase the 20kHz frequency as much as possible, we would like to avoid overloading the CPU using the DMA for this.

We would like to do something like use a timer to trigger the transmission and the DMA can save the RX data in a circular buffer. Our main function is going to take the last updated value, but it does not need to be synchronised. So, we only need a buffer of one single value of 64bit.

I have been trying many ways to do it, but I do not get to trigger the SPI. This is the last code I have created using the graphical interface of STMCubeIDE and LL libraries trying to do a simple example that sends a byte just to see if the clock is generated at the output, but it does not seem to be doing anything.

Spoiler

#include "main.h"

/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */

/* USER CODE END Includes */

/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */

/* USER CODE END PTD */

/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
volatile uint8_t source = 123;
volatile uint8_t destination = 0;
/* USER CODE END PD */

/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */

/* USER CODE END PM */

/* Private variables ---------------------------------------------------------*/

/* USER CODE BEGIN PV */

/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_DMA_Init(void);
static void MX_TIM2_Init(void);
static void MX_TIM3_Init(void);
static void MX_SPI3_Init(void);
/* USER CODE BEGIN PFP */
/* USER CODE END PFP */

/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */

/* USER CODE END 0 */

/**
  * @brief  The application entry point.
  * @retval int
  */
int main(void)
{

  /* USER CODE BEGIN 1 */

  /* USER CODE END 1 */

  /* MCU Configuration--------------------------------------------------------*/

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  LL_APB2_GRP1_EnableClock(LL_APB2_GRP1_PERIPH_SYSCFG);
  LL_APB1_GRP1_EnableClock(LL_APB1_GRP1_PERIPH_PWR);

  /* System interrupt init*/
  NVIC_SetPriorityGrouping(NVIC_PRIORITYGROUP_4);

  /* SysTick_IRQn interrupt configuration */
  NVIC_SetPriority(SysTick_IRQn, NVIC_EncodePriority(NVIC_GetPriorityGrouping(),15, 0));

  /** Disable the internal Pull-Up in Dead Battery pins of UCPD peripheral
  */
  LL_PWR_DisableUCPDDeadBattery();

  /* USER CODE BEGIN Init */

  /* USER CODE END Init */

  /* Configure the system clock */
  SystemClock_Config();

  /* USER CODE BEGIN SysInit */

  /* USER CODE END SysInit */

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_DMA_Init();
  MX_TIM2_Init();
  MX_TIM3_Init();
  MX_SPI3_Init();
  /* USER CODE BEGIN 2 */
  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
  }
  /* USER CODE END 3 */
}

/**
  * @brief System Clock Configuration
  * @retval None
  */
void SystemClock_Config(void)
{
  LL_FLASH_SetLatency(LL_FLASH_LATENCY_4);
  while(LL_FLASH_GetLatency() != LL_FLASH_LATENCY_4)
  {
  }
  LL_PWR_EnableRange1BoostMode();
  LL_RCC_HSI_Enable();
   /* Wait till HSI is ready */
  while(LL_RCC_HSI_IsReady() != 1)
  {
  }

  LL_RCC_HSI_SetCalibTrimming(64);
  LL_RCC_PLL_ConfigDomain_SYS(LL_RCC_PLLSOURCE_HSI, LL_RCC_PLLM_DIV_4, 85, LL_RCC_PLLR_DIV_2);
  LL_RCC_PLL_EnableDomain_SYS();
  LL_RCC_PLL_Enable();
   /* Wait till PLL is ready */
  while(LL_RCC_PLL_IsReady() != 1)
  {
  }

  LL_RCC_SetSysClkSource(LL_RCC_SYS_CLKSOURCE_PLL);
  LL_RCC_SetAHBPrescaler(LL_RCC_SYSCLK_DIV_2);
   /* Wait till System clock is ready */
  while(LL_RCC_GetSysClkSource() != LL_RCC_SYS_CLKSOURCE_STATUS_PLL)
  {
  }

  /* Insure 1us transition state at intermediate medium speed clock*/
  for (__IO uint32_t i = (170 >> 1); i !=0; i--);

  /* Set AHB prescaler*/
  LL_RCC_SetAHBPrescaler(LL_RCC_SYSCLK_DIV_1);
  LL_RCC_SetAPB1Prescaler(LL_RCC_APB1_DIV_1);
  LL_RCC_SetAPB2Prescaler(LL_RCC_APB2_DIV_1);

  LL_Init1msTick(170000000);

  LL_SetSystemCoreClock(170000000);
}

/**
  * @brief SPI3 Initialization Function
  * @PAram None
  * @retval None
  */
static void MX_SPI3_Init(void)
{

  /* USER CODE BEGIN SPI3_Init 0 */

  /* USER CODE END SPI3_Init 0 */

  LL_SPI_InitTypeDef SPI_InitStruct = {0};

  LL_GPIO_InitTypeDef GPIO_InitStruct = {0};

  /* Peripheral clock enable */
  LL_APB1_GRP1_EnableClock(LL_APB1_GRP1_PERIPH_SPI3);

  LL_AHB2_GRP1_EnableClock(LL_AHB2_GRP1_PERIPH_GPIOB);
  LL_AHB2_GRP1_EnableClock(LL_AHB2_GRP1_PERIPH_GPIOC);
  /**SPI3 GPIO Configuration
  PB3   ------> SPI3_SCK
  PC12   ------> SPI3_MOSI
  PB4   ------> SPI3_MISO
  */
  GPIO_InitStruct.Pin = LL_GPIO_PIN_3;
  GPIO_InitStruct.Mode = LL_GPIO_MODE_ALTERNATE;
  GPIO_InitStruct.Speed = LL_GPIO_SPEED_FREQ_LOW;
  GPIO_InitStruct.OutputType = LL_GPIO_OUTPUT_PUSHPULL;
  GPIO_InitStruct.Pull = LL_GPIO_PULL_NO;
  GPIO_InitStruct.Alternate = LL_GPIO_AF_6;
  LL_GPIO_Init(GPIOB, &GPIO_InitStruct);

  GPIO_InitStruct.Pin = LL_GPIO_PIN_12;
  GPIO_InitStruct.Mode = LL_GPIO_MODE_ALTERNATE;
  GPIO_InitStruct.Speed = LL_GPIO_SPEED_FREQ_LOW;
  GPIO_InitStruct.OutputType = LL_GPIO_OUTPUT_PUSHPULL;
  GPIO_InitStruct.Pull = LL_GPIO_PULL_NO;
  GPIO_InitStruct.Alternate = LL_GPIO_AF_6;
  LL_GPIO_Init(GPIOC, &GPIO_InitStruct);

  GPIO_InitStruct.Pin = LL_GPIO_PIN_4;
  GPIO_InitStruct.Mode = LL_GPIO_MODE_ALTERNATE;
  GPIO_InitStruct.Speed = LL_GPIO_SPEED_FREQ_LOW;
  GPIO_InitStruct.OutputType = LL_GPIO_OUTPUT_PUSHPULL;
  GPIO_InitStruct.Pull = LL_GPIO_PULL_NO;
  GPIO_InitStruct.Alternate = LL_GPIO_AF_6;
  LL_GPIO_Init(GPIOB, &GPIO_InitStruct);

  /* SPI3 DMA Init */

  /* SPI3_RX Init */
  LL_DMA_SetPeriphRequest(DMA1, LL_DMA_CHANNEL_2, LL_DMAMUX_REQ_SPI3_RX);

  LL_DMA_SetDataTransferDirection(DMA1, LL_DMA_CHANNEL_2, LL_DMA_DIRECTION_PERIPH_TO_MEMORY);

  LL_DMA_SetChannelPriorityLevel(DMA1, LL_DMA_CHANNEL_2, LL_DMA_PRIORITY_LOW);

  LL_DMA_SetMode(DMA1, LL_DMA_CHANNEL_2, LL_DMA_MODE_NORMAL);

  LL_DMA_SetPeriphIncMode(DMA1, LL_DMA_CHANNEL_2, LL_DMA_PERIPH_NOINCREMENT);

  LL_DMA_SetMemoryIncMode(DMA1, LL_DMA_CHANNEL_2, LL_DMA_MEMORY_NOINCREMENT);

  LL_DMA_SetPeriphSize(DMA1, LL_DMA_CHANNEL_2, LL_DMA_PDATAALIGN_BYTE);

  LL_DMA_SetMemorySize(DMA1, LL_DMA_CHANNEL_2, LL_DMA_MDATAALIGN_BYTE);

  /* USER CODE BEGIN SPI3_Init 1 */
  LL_DMA_ConfigAddresses(DMA1, LL_DMA_CHANNEL_2, (uint32_t)&SPI3->DR, (uint32_t)&destination,LL_DMA_GetDataTransferDirection(DMA1, LL_DMA_CHANNEL_2));
  LL_DMA_SetDataLength(DMA1, LL_DMA_CHANNEL_2, 1);
  LL_DMA_EnableIT_TC(DMA1, LL_DMA_CHANNEL_2);
  LL_DMA_EnableChannel(DMA1, LL_DMA_CHANNEL_2);
  /* USER CODE END SPI3_Init 1 */
  /* SPI3 parameter configuration*/
  SPI_InitStruct.TransferDirection = LL_SPI_FULL_DUPLEX;
  SPI_InitStruct.Mode = LL_SPI_MODE_MASTER;
  SPI_InitStruct.DataWidth = LL_SPI_DATAWIDTH_8BIT;
  SPI_InitStruct.ClockPolarity = LL_SPI_POLARITY_LOW;
  SPI_InitStruct.ClockPhase = LL_SPI_PHASE_2EDGE;
  SPI_InitStruct.NSS = LL_SPI_NSS_SOFT;
  SPI_InitStruct.BaudRate = LL_SPI_BAUDRATEPRESCALER_DIV64;
  SPI_InitStruct.BitOrder = LL_SPI_MSB_FIRST;
  SPI_InitStruct.CRCCalculation = LL_SPI_CRCCALCULATION_DISABLE;
  SPI_InitStruct.CRCPoly = 7;
  LL_SPI_Init(SPI3, &SPI_InitStruct);
  LL_SPI_SetStandard(SPI3, LL_SPI_PROTOCOL_MOTOROLA);
  LL_SPI_DisableNSSPulseMgt(SPI3);
  /* USER CODE BEGIN SPI3_Init 2 */
  LL_SPI_Enable(SPI3);
  LL_SPI_EnableDMAReq_RX(SPI3);
  /* USER CODE END SPI3_Init 2 */

}

/**
  * @brief TIM2 Initialization Function
  * @PAram None
  * @retval None
  */
static void MX_TIM2_Init(void)
{

  /* USER CODE BEGIN TIM2_Init 0 */

  /* USER CODE END TIM2_Init 0 */

  LL_TIM_InitTypeDef TIM_InitStruct = {0};
  LL_TIM_OC_InitTypeDef TIM_OC_InitStruct = {0};

  LL_GPIO_InitTypeDef GPIO_InitStruct = {0};

  /* Peripheral clock enable */
  LL_APB1_GRP1_EnableClock(LL_APB1_GRP1_PERIPH_TIM2);

  /* USER CODE BEGIN TIM2_Init 1 */

  /* USER CODE END TIM2_Init 1 */
  TIM_InitStruct.Prescaler = 169;
  TIM_InitStruct.CounterMode = LL_TIM_COUNTERMODE_UP;
  TIM_InitStruct.Autoreload = 254;
  TIM_InitStruct.ClockDivision = LL_TIM_CLOCKDIVISION_DIV1;
  LL_TIM_Init(TIM2, &TIM_InitStruct);
  LL_TIM_EnableARRPreload(TIM2);
  LL_TIM_OC_EnablePreload(TIM2, LL_TIM_CHANNEL_CH1);
  TIM_OC_InitStruct.OCMode = LL_TIM_OCMODE_PWM1;
  TIM_OC_InitStruct.OCState = LL_TIM_OCSTATE_DISABLE;
  TIM_OC_InitStruct.OCNState = LL_TIM_OCSTATE_DISABLE;
  TIM_OC_InitStruct.CompareValue = 255;
  TIM_OC_InitStruct.OCPolarity = LL_TIM_OCPOLARITY_HIGH;
  LL_TIM_OC_Init(TIM2, LL_TIM_CHANNEL_CH1, &TIM_OC_InitStruct);
  LL_TIM_OC_DisableFast(TIM2, LL_TIM_CHANNEL_CH1);
  LL_TIM_OC_EnablePreload(TIM2, LL_TIM_CHANNEL_CH2);
  LL_TIM_OC_Init(TIM2, LL_TIM_CHANNEL_CH2, &TIM_OC_InitStruct);
  LL_TIM_OC_DisableFast(TIM2, LL_TIM_CHANNEL_CH2);
  LL_TIM_OC_EnablePreload(TIM2, LL_TIM_CHANNEL_CH3);
  LL_TIM_OC_Init(TIM2, LL_TIM_CHANNEL_CH3, &TIM_OC_InitStruct);
  LL_TIM_OC_DisableFast(TIM2, LL_TIM_CHANNEL_CH3);
  LL_TIM_SetTriggerOutput(TIM2, LL_TIM_TRGO_RESET);
  LL_TIM_DisableMasterSlaveMode(TIM2);
  /* USER CODE BEGIN TIM2_Init 2 */
  LL_TIM_CC_EnableChannel(TIM2, LL_TIM_CHANNEL_CH1);
  LL_TIM_CC_EnableChannel(TIM2, LL_TIM_CHANNEL_CH2);
  LL_TIM_CC_EnableChannel(TIM2, LL_TIM_CHANNEL_CH3);
  LL_TIM_EnableCounter(TIM2);
  /* USER CODE END TIM2_Init 2 */
  LL_AHB2_GRP1_EnableClock(LL_AHB2_GRP1_PERIPH_GPIOD);
  LL_AHB2_GRP1_EnableClock(LL_AHB2_GRP1_PERIPH_GPIOA);
  /**TIM2 GPIO Configuration
  PD4   ------> TIM2_CH2
  PD7   ------> TIM2_CH3
  PA15   ------> TIM2_CH1
  */
  GPIO_InitStruct.Pin = LL_GPIO_PIN_4;
  GPIO_InitStruct.Mode = LL_GPIO_MODE_ALTERNATE;
  GPIO_InitStruct.Speed = LL_GPIO_SPEED_FREQ_LOW;
  GPIO_InitStruct.OutputType = LL_GPIO_OUTPUT_PUSHPULL;
  GPIO_InitStruct.Pull = LL_GPIO_PULL_NO;
  GPIO_InitStruct.Alternate = LL_GPIO_AF_2;
  LL_GPIO_Init(GPIOD, &GPIO_InitStruct);

  GPIO_InitStruct.Pin = LL_GPIO_PIN_7;
  GPIO_InitStruct.Mode = LL_GPIO_MODE_ALTERNATE;
  GPIO_InitStruct.Speed = LL_GPIO_SPEED_FREQ_LOW;
  GPIO_InitStruct.OutputType = LL_GPIO_OUTPUT_PUSHPULL;
  GPIO_InitStruct.Pull = LL_GPIO_PULL_NO;
  GPIO_InitStruct.Alternate = LL_GPIO_AF_2;
  LL_GPIO_Init(GPIOD, &GPIO_InitStruct);

  GPIO_InitStruct.Pin = LL_GPIO_PIN_15;
  GPIO_InitStruct.Mode = LL_GPIO_MODE_ALTERNATE;
  GPIO_InitStruct.Speed = LL_GPIO_SPEED_FREQ_LOW;
  GPIO_InitStruct.OutputType = LL_GPIO_OUTPUT_PUSHPULL;
  GPIO_InitStruct.Pull = LL_GPIO_PULL_NO;
  GPIO_InitStruct.Alternate = LL_GPIO_AF_1;
  LL_GPIO_Init(GPIOA, &GPIO_InitStruct);

}

/**
  * @brief TIM3 Initialization Function
  * @PAram None
  * @retval None
  */
static void MX_TIM3_Init(void)
{

  /* USER CODE BEGIN TIM3_Init 0 */

  /* USER CODE END TIM3_Init 0 */

  LL_TIM_InitTypeDef TIM_InitStruct = {0};

  /* Peripheral clock enable */
  LL_APB1_GRP1_EnableClock(LL_APB1_GRP1_PERIPH_TIM3);

  /* TIM3 DMA Init */

  /* TIM3_UP Init */
  LL_DMA_SetPeriphRequest(DMA1, LL_DMA_CHANNEL_1, LL_DMAMUX_REQ_TIM3_UP);

  LL_DMA_SetDataTransferDirection(DMA1, LL_DMA_CHANNEL_1, LL_DMA_DIRECTION_PERIPH_TO_MEMORY);

  LL_DMA_SetChannelPriorityLevel(DMA1, LL_DMA_CHANNEL_1, LL_DMA_PRIORITY_LOW);

  LL_DMA_SetMode(DMA1, LL_DMA_CHANNEL_1, LL_DMA_MODE_CIRCULAR);

  LL_DMA_SetPeriphIncMode(DMA1, LL_DMA_CHANNEL_1, LL_DMA_PERIPH_NOINCREMENT);

  LL_DMA_SetMemoryIncMode(DMA1, LL_DMA_CHANNEL_1, LL_DMA_MEMORY_NOINCREMENT);

  LL_DMA_SetPeriphSize(DMA1, LL_DMA_CHANNEL_1, LL_DMA_PDATAALIGN_BYTE);

  LL_DMA_SetMemorySize(DMA1, LL_DMA_CHANNEL_1, LL_DMA_MDATAALIGN_BYTE);

  /* USER CODE BEGIN TIM3_Init 1 */
  LL_DMA_ConfigAddresses(DMA1, LL_DMA_CHANNEL_1, (uint32_t)&source, (uint32_t)&SPI3->DR,LL_DMA_GetDataTransferDirection(DMA1, LL_DMA_CHANNEL_1));
  LL_DMA_SetDataLength(DMA1, LL_DMA_CHANNEL_1, 1);
  LL_DMA_EnableIT_TC(DMA1, LL_DMA_CHANNEL_1);
  LL_DMA_EnableChannel(DMA1, LL_DMA_CHANNEL_1);
  /* USER CODE END TIM3_Init 1 */
  TIM_InitStruct.Prescaler = 16999;
  TIM_InitStruct.CounterMode = LL_TIM_COUNTERMODE_UP;
  TIM_InitStruct.Autoreload = 9999;
  TIM_InitStruct.ClockDivision = LL_TIM_CLOCKDIVISION_DIV1;
  LL_TIM_Init(TIM3, &TIM_InitStruct);
  LL_TIM_DisableARRPreload(TIM3);
  LL_TIM_SetClockSource(TIM3, LL_TIM_CLOCKSOURCE_INTERNAL);
  LL_TIM_SetTriggerOutput(TIM3, LL_TIM_TRGO_UPDATE);
  LL_TIM_DisableMasterSlaveMode(TIM3);
  /* USER CODE BEGIN TIM3_Init 2 */
  LL_TIM_EnableCounter(TIM3);
  LL_TIM_EnableDMAReq_UPDATE(TIM3);
  /* USER CODE END TIM3_Init 2 */

}

/**
  * Enable DMA controller clock
  */
static void MX_DMA_Init(void)
{

  /* Init with LL driver */
  /* DMA controller clock enable */
  LL_AHB1_GRP1_EnableClock(LL_AHB1_GRP1_PERIPH_DMAMUX1);
  LL_AHB1_GRP1_EnableClock(LL_AHB1_GRP1_PERIPH_DMA1);

  /* DMA interrupt init */
  /* DMA1_Channel1_IRQn interrupt configuration */
  NVIC_SetPriority(DMA1_Channel1_IRQn, NVIC_EncodePriority(NVIC_GetPriorityGrouping(),0, 0));
  NVIC_EnableIRQ(DMA1_Channel1_IRQn);
  /* DMA1_Channel2_IRQn interrupt configuration */
  NVIC_SetPriority(DMA1_Channel2_IRQn, NVIC_EncodePriority(NVIC_GetPriorityGrouping(),0, 0));
  NVIC_EnableIRQ(DMA1_Channel2_IRQn);

}

/**
  * @brief GPIO Initialization Function
  * @PAram None
  * @retval None
  */
static void MX_GPIO_Init(void)
{
  LL_GPIO_InitTypeDef GPIO_InitStruct = {0};
  /* USER CODE BEGIN MX_GPIO_Init_1 */

  /* USER CODE END MX_GPIO_Init_1 */

  /* GPIO Ports Clock Enable */
  LL_AHB2_GRP1_EnableClock(LL_AHB2_GRP1_PERIPH_GPIOB);
  LL_AHB2_GRP1_EnableClock(LL_AHB2_GRP1_PERIPH_GPIOD);
  LL_AHB2_GRP1_EnableClock(LL_AHB2_GRP1_PERIPH_GPIOC);
  LL_AHB2_GRP1_EnableClock(LL_AHB2_GRP1_PERIPH_GPIOA);

  /**/
  GPIO_InitStruct.Pin = LL_GPIO_PIN_8;
  GPIO_InitStruct.Mode = LL_GPIO_MODE_INPUT;
  GPIO_InitStruct.Pull = LL_GPIO_PULL_NO;
  LL_GPIO_Init(GPIOB, &GPIO_InitStruct);

  /* USER CODE BEGIN MX_GPIO_Init_2 */

  /* USER CODE END MX_GPIO_Init_2 */
}

Then I have this simple function in the interruption of the DMA RX to check if the DMA has received something. Using the debug and a breakpoint I can check it.

Spoiler

void DMA1_Channel2_IRQHandler(void)
{
  /* USER CODE BEGIN DMA1_Channel2_IRQn 0 */
  if (LL_DMA_IsActiveFlag_TC1(DMA1)) {
	LL_DMA_ClearFlag_TC1(DMA1);
  }
  /* USER CODE END DMA1_Channel2_IRQn 0 */
  /* USER CODE BEGIN DMA1_Channel2_IRQn 1 */

  /* USER CODE END DMA1_Channel2_IRQn 1 */
}

Thank you in advanced.