I'm using STM32F100RBT6. The goal is to use TIM3 CH3 to generate a PWM signal with different duty cycle using DMA transfer.

[costi]

I have configured TIM3 (using CubeIDE) in such a way that it generates an event that is used to transfer measurements on the ADC channels to memory using DMA. This works.

But in the same time, I want to transfer to TIM3 CH3 the values in a table. The values are different. But this does not happen. The PWM signal generated is always with the 50% duty cycle as set using CubeIDE.

I can't figure out what else I need to do to execute the transfer of values from the table to the timer via DMA.

I want to use LL library or direct register configuration.

In the attached code in the user section I have added the necessary code to start timer 3 and DMA.

Excluding the use of HAL for now.

Some advice is welcome.

Thanks

below is TIM3 settings

pheripheral clock is 24KHz and the PWM signal is 8KHz

void MX_TIM3_Init(void)

{

 /* USER CODE BEGIN TIM3_Init 0 */

 /* USER CODE END TIM3_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_TIM3);

 /* TIM3 DMA Init */

 /* TIM3_CH3 Init */

 LL_DMA_SetDataTransferDirection(DMA1, LL_DMA_CHANNEL_2, LL_DMA_DIRECTION_MEMORY_TO_PERIPH);

 LL_DMA_SetChannelPriorityLevel(DMA1, LL_DMA_CHANNEL_2, LL_DMA_PRIORITY_LOW);

 LL_DMA_SetMode(DMA1, LL_DMA_CHANNEL_2, LL_DMA_MODE_CIRCULAR);

 LL_DMA_SetPeriphIncMode(DMA1, LL_DMA_CHANNEL_2, LL_DMA_PERIPH_NOINCREMENT);

 LL_DMA_SetMemoryIncMode(DMA1, LL_DMA_CHANNEL_2, LL_DMA_MEMORY_INCREMENT);

 LL_DMA_SetPeriphSize(DMA1, LL_DMA_CHANNEL_2, LL_DMA_PDATAALIGN_HALFWORD);

 LL_DMA_SetMemorySize(DMA1, LL_DMA_CHANNEL_2, LL_DMA_MDATAALIGN_HALFWORD);

 /* USER CODE BEGIN TIM3_Init 1 */

 /* USER CODE END TIM3_Init 1 */

 TIM_InitStruct.Prescaler = 0;

 TIM_InitStruct.CounterMode = LL_TIM_COUNTERMODE_UP;

 TIM_InitStruct.Autoreload = 3000;

 TIM_InitStruct.ClockDivision = LL_TIM_CLOCKDIVISION_DIV1;

 LL_TIM_Init(TIM3, &TIM_InitStruct);

 LL_TIM_EnableARRPreload(TIM3);

 LL_TIM_SetClockSource(TIM3, LL_TIM_CLOCKSOURCE_INTERNAL);

 LL_TIM_OC_EnablePreload(TIM3, 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 = 1500;

 TIM_OC_InitStruct.OCPolarity = LL_TIM_OCPOLARITY_HIGH;

 LL_TIM_OC_Init(TIM3, LL_TIM_CHANNEL_CH1, &TIM_OC_InitStruct);

 LL_TIM_OC_DisableFast(TIM3, LL_TIM_CHANNEL_CH1);

 LL_TIM_OC_EnablePreload(TIM3, LL_TIM_CHANNEL_CH3);

 LL_TIM_OC_Init(TIM3, LL_TIM_CHANNEL_CH3, &TIM_OC_InitStruct);

 LL_TIM_OC_DisableFast(TIM3, LL_TIM_CHANNEL_CH3);

 LL_TIM_SetTriggerOutput(TIM3, LL_TIM_TRGO_UPDATE);

 LL_TIM_DisableMasterSlaveMode(TIM3);

 /* USER CODE BEGIN TIM3_Init 2 */

 LL_TIM_CC_EnableChannel(TIM3, LL_TIM_CHANNEL_CH1);      // EVENT for DMA

 LL_TIM_CC_EnableChannel(TIM3, LL_TIM_CHANNEL_CH3);      // PWM

 //LL_TIM_EnableUpdateEvent(TIM3);

 LL_TIM_EnableCounter(TIM3);

 /* prepare DMA*/

 /* buffer contains 22 diferrent values */

 LL_DMA_SetDataLength(DMA1, LL_DMA_CHANNEL_2, 22);   // number of data to transfer

 LL_DMA_ConfigAddresses(DMA1, LL_DMA_CHANNEL_2, (INT32U)&(TIM3->CCR3), (INT32U)(&buffer), LL_DMA_DIRECTION_MEMORY_TO_PERIPH); // buffer to transmit to the TIM3_CH3 using DMA

 LL_TIM_EnableDMAReq_UPDATE(TIM3);

 LL_TIM_GenerateEvent_UPDATE(TIM3);

 /* USER CODE END TIM3_Init 2 */

 LL_APB2_GRP1_EnableClock(LL_APB2_GRP1_PERIPH_GPIOB);

   /**TIM3 GPIO Configuration

   PB0    ------> TIM3_CH3

   */

 GPIO_InitStruct.Pin = PWM_SENSOR_Pin;

 GPIO_InitStruct.Mode = LL_GPIO_MODE_ALTERNATE;

 GPIO_InitStruct.Speed = LL_GPIO_SPEED_FREQ_LOW;

 GPIO_InitStruct.OutputType = LL_GPIO_OUTPUT_PUSHPULL;

 LL_GPIO_Init(PWM_SENSOR_GPIO_Port, &GPIO_InitStruct);

}

[gbm]

I can't see any call actually enabling/starting the DMA channel - this should be the last DMA config call.

[waclawek.jan]

I don't see DMA clock to be enabled in RCC, either.

At any case, always start debugging by reading out and checking the related peripherals' registers' content.

JW

[costi]

OK, thank you for your fast answer.

I forgot about this line

LL_DMA_EnableChannel(DMA1, LL_DMA_CHANNEL_2);

although a siilar one I'm used to start DMA CH1 for ADC

but it's not enough

I have to understand how the transfer can be start

[costi]

Thank you for the answer,

the clock is configured in another section of my cod.

void MX_DMA_Init(void)

{

 /* Init with LL driver */

 /* DMA controller clock enable */

 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(),2, 0));

 NVIC_EnableIRQ(DMA1_Channel1_IRQn);

}

As I explained I am using the DMA for ADC and it is working well.

And also I want to use it for TIM3 CH3.

In the init phase the function MX_DMA_Init() is called before ti init ADC and TIM pheripherals