STM32 DAC Trigger

Question

I am Trying to use the DAC output on my STM32L053R8 NUCLEO Board. I generate the corresponding Sin-Wave values to set the DAC Values like this.

 // Resolution for DAC
 for(i=0; i<= 249; i++)
 {
 dacVal[i]= 2048*(sin(i*2*pi/250)+1);
 } 

In the Main function i use the while loop to write the values to the DAC.

 while (1)
 { 
 for(i=0; i<=249; i++)
 { 
 HAL_DAC_SetValue(&hdac, DAC1_CHANNEL_1,DAC_ALIGN_12B_R, dacVal[i]);
 }
 i=0; 
 } 

The Result is a nice Sine Wave with a peak-peak Voltage of 3.3V and a Frequency of 200Hz. I generated the init code with CubeMX.

Now i want to increase the Frequency of the DAC output. I initialized the DAC with this Function:

static void MX_DAC_Init(void)
{
 DAC_ChannelConfTypeDef sConfig = {0};
 /*DAC Initialization*/
 hdac.Instance = DAC;
 if (HAL_DAC_Init(&hdac) != HAL_OK)
 {
 Error_Handler();
 }
 /*DAC channel OUT1 config*/
 sConfig.DAC_Trigger = DAC_TRIGGER_NONE;
 sConfig.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE;
 if (HAL_DAC_ConfigChannel(&hdac, &sConfig, DAC_CHANNEL_1) != HAL_OK)
 {
 Error_Handler();
 }
}

And my TIM6 like this:

static void MX_TIM6_Init(void)
{
 TIM_MasterConfigTypeDef sMasterConfig = {0};
 htim6.Instance = TIM6;
 htim6.Init.Prescaler = 2;
 htim6.Init.CounterMode = TIM_COUNTERMODE_UP;
 htim6.Init.Period = 1000;
 htim6.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
 if (HAL_TIM_Base_Init(&htim6) != HAL_OK)
 {
 Error_Handler();
 }
 sMasterConfig.MasterOutputTrigger = TIM_TRGO_ENABLE;
 sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
 if (HAL_TIMEx_MasterConfigSynchronization(&htim6, &sMasterConfig) != HAL_OK)
 {
 Error_Handler();
 }
}

The code generates a Sin-Wave like i need it. But if i change

sConfig.DAC_Trigger = DAC_TRIGGER_NONE;

to

sConfig.DAC_Trigger = DAC_TRIGGER_T6_TRGO;

There is no Output anymore. I Assume that the Output is triggered by the Timer TIM6 but its somehow not working like that. I think there is something wrong with my Timer init function. At the end i just want to put my ouput frequency of the Sin-Wave to 40khz.

• Marcus Müller: hint: 3/4 of your table are superfluous, since sin is odd-symmetric to \$\pi\$ and within \$[0;\pi]\$ even-symmetric to \$\frac\pi2\$. Use the extra space for a better resolution, or reduce the necessary memory bandwidth if you have caches (the stm32l0 probably has no caches, though)

Answer 1

STMCubeMX has generated the TIM6 Init code for you but it has not started the timer, you need to call the HAL_TIM_Base_Start() function after calling MX_TIM6_Init so that TIM6 CR1 has CEN bit set which starts the timer running.

• Walter Nazarenus: I did start the Timer and the DAC after i initialized all the peripheral. HAL_TIM_Base_Start_IT(&htim6); HAL_DAC_Start(&hdac, DAC_CHANNEL_1)