I want to use the Discovery kit with STM32H745XI MCU to generate sawtooth waves.

[Ateam]

The Discovery kit with STM32H745XI MCU outputs a triangle wave, but how can I make it output a sawtooth wave instead of a triangle wave?
Please let me know the specific improvement and source code.
Looking forward to your answer.

[KDJEM.1]

Hello @Ateam and welcome to the community 🙂,

You can use DAC to generate a sawtooth wave.

For that, I advise you to take a look to this wiki page Getting started with DAC - stm32mcu.

This wiki example used NUCLEO-L476RG board but it can be easily tailored to any other board.

I hope this help you!

Kaouthar

[Tesla DeLorean]

The DAC will output any waveform you describe in the pattern buffer.

[SofLit · Accepted solution]

Hello,

Triangle wave generation is a DAC HW feature.

Sawtooth you need to generate it by software by samples using a lookup table like done for the escalator wave generation.

The escalator wave generation is the one you need:

const uint8_t aEscalator8bit[6] = {0x0, 0x33, 0x66, 0x99, 0xCC, 0xFF};

static void DAC_Ch1_EscalatorConfig(void)
{
  /*##-1- Initialize the DAC peripheral ######################################*/
  if (HAL_DAC_Init(&DacHandle) != HAL_OK)
  {
    /* Initialization Error */
    Error_Handler();
  }

  /*##-1- DAC channel1 Configuration #########################################*/
  sConfig.DAC_Trigger = DAC_TRIGGER_T6_TRGO;
  sConfig.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE;

  if (HAL_DAC_ConfigChannel(&DacHandle, &sConfig, DACx_CHANNEL) != HAL_OK)
  {
    /* Channel configuration Error */
    Error_Handler();
  }

  /*##-2- Enable DAC selected channel and associated DMA #############################*/
  if (HAL_DAC_Start_DMA(&DacHandle, DACx_CHANNEL, (uint32_t *)aEscalator8bit, 6, DAC_ALIGN_8B_R) != HAL_OK)
  {
    /* Start DMA Error */
    Error_Handler();
  }
}

Meanwhile, you need to increase the samples as much as possible with a short time between samples to be nearest as much as possible to a sawtooth wave.