Configuring Timer3 for capture Compare input with DMA on CH4. STM32H750

Hi AScha.3

Thanks for checking CubeMX, it looks like I needed to put PINB_1 into AF2_TIM3_CH4 before the other UI would recognize and use PB1.

Regarding your question about the trigger, I'm actually unsure what it is triggering on currently, the mux seems to be setup for CH4 output (code below). What I want it to trigger on is: both edges of the signal on PB1 input capture (the input signal is about 1Mhz). So on both edges I want the DMA to capture the (tim3) counter value and write it into a buffer in sram, while incrementing the offset.

#define SRAM1_DATA __attribute__((section(".sram1_bss")))

SRAM1_DATA uint16_t SDataBuffer[160];

TIM_ClockConfigTypeDef sClockSourceConfig = {0};

  TIM_MasterConfigTypeDef sMasterConfig = {0};

  TIM_IC_InitTypeDef sConfigIC = {0};

  TIM_SlaveConfigTypeDef sSlaveConfig = {0};

  htim3.Instance = TIM3;

  htim3.Init.Prescaler = 0;

  htim3.Init.CounterMode = TIM_COUNTERMODE_UP;

  htim3.Init.Period = 65535;

  htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;

  htim3.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;

  if (HAL_TIM_Base_Init(&htim3) != HAL_OK)

  {

    Error_Handler();

  }

  sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;

  if (HAL_TIM_ConfigClockSource(&htim3, &sClockSourceConfig) != HAL_OK)

  {

    Error_Handler();

  }

  if (HAL_TIM_IC_Init(&htim3) != HAL_OK)

  {

    Error_Handler();

  }

  sMasterConfig.MasterOutputTrigger = TIM_TRGO_ENABLE;

  sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;

  if (HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig) != HAL_OK)

  {

    Error_Handler();

  }

  sConfigIC.ICPolarity = TIM_INPUTCHANNELPOLARITY_BOTHEDGE;

  sConfigIC.ICSelection = TIM_ICSELECTION_DIRECTTI;

  sConfigIC.ICPrescaler = TIM_ICPSC_DIV1;

  sConfigIC.ICFilter = 0;

  if (HAL_TIM_IC_ConfigChannel(&htim3, &sConfigIC, TIM_CHANNEL_4) != HAL_OK)

  {

    Error_Handler();

  }

  GPIO_InitTypeDef GPIO_InitStruct = {0};

  HAL_DMA_MuxSyncConfigTypeDef pSyncConfig;

  __HAL_RCC_TIM3_CLK_ENABLE();

  GPIO_InitStruct.Pin = GPIO_PIN_1;

  GPIO_InitStruct.Mode = GPIO_MODE_INPUT;

  GPIO_InitStruct.Pull = GPIO_PULLUP;

  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;

  GPIO_InitStruct.Alternate = GPIO_AF2_TIM3;

  HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);

  hdma_tim3_ch4.Instance = DMA1_Stream5;

  hdma_tim3_ch4.Init.Request = DMA_REQUEST_TIM3_CH4;

  hdma_tim3_ch4.Init.Direction = DMA_PERIPH_TO_MEMORY;

  hdma_tim3_ch4.Init.PeriphInc = DMA_PINC_DISABLE;

  hdma_tim3_ch4.Init.MemInc = DMA_MINC_ENABLE;

  hdma_tim3_ch4.Init.PeriphDataAlignment = DMA_PDATAALIGN_HALFWORD;

  hdma_tim3_ch4.Init.MemDataAlignment = DMA_MDATAALIGN_HALFWORD;

  hdma_tim3_ch4.Init.Mode = DMA_CIRCULAR;

  hdma_tim3_ch4.Init.Priority = DMA_PRIORITY_LOW;

  hdma_tim3_ch4.Init.FIFOMode = DMA_FIFOMODE_ENABLE;

  hdma_tim3_ch4.Init.FIFOThreshold = DMA_FIFO_THRESHOLD_FULL;

  hdma_tim3_ch4.Init.MemBurst = DMA_MBURST_SINGLE;

  hdma_tim3_ch4.Init.PeriphBurst = DMA_PBURST_SINGLE;

  if (HAL_DMA_Init(&hdma_tim3_ch4) != HAL_OK)

  {

    Error_Handler();

  }

  __HAL_RCC_DMA1_CLK_ENABLE();

  __HAL_LINKDMA(&htim3, hdma[TIM_DMA_ID_CC4], hdma_tim3_ch4);

  HAL_TIM_IC_Start_DMA(&htim3, TIM_CHANNEL_4, (uint32_t*)&(SDataBuffer[0]), sizeof(SDataBuffer) / sizeof(SDataBuffer[0]));

  // GPIOC_PIN4 is connected to GIOPB_PIN1 for test purposes.

  while (1) {

    GPIOC->BSRR = (1 << 4) << 16;

    volatile uint32_t x = 540;

    while (x--) {}

    GPIOC->BSRR = (1 << 4);

    x = 540;

    while (x--) {}

  }

@AScha.3​ 

>> just: what you want to do with this ?

I'm attempting to time the polarity changes on PinB_1 which are encoded bits based on pulse width. I want to offload the timing from the CM7, with a maximum transfer size being 10 bytes. At maximum: 10 * 8 * 2 = 160 captures (2 edges per bit) this way the CM7 can defer handling the data instead of missing it or having to interrupt something else important.

I do not have IOs left that connect to any CH1/CH2 combo and TIM3_CH4 (on PB1) seems to be the only pin that I have left connecting to a timer.

The timing is 4us per bit, 1us minimum pulse width.

After enabling the "internal clock" on the timer through Cube, I now do not see the DMA occurring at all.

I also do not see the CCR4 register change, while I know the signal on PB1 is changing (verified through a logic analyzer).

Do I need slave mode?

TIxFPy seem to all need a second IO pin which I do not have. Is there any way around this?