STM32U5: in Stop 2 mode, ADC sampling abnormal when waking periodically by LPTimer

[lsc]

"In the STM32U5, the LPTimer is used to periodically wake up from Stop 2 mode to sample ADC data. After the ADC samples the data via DMA and generates an interrupt, the system re-enters Stop 2 mode. When using a debugger, the sampled data is normal. However, when the device is running, the sampled data is not correct.

[lsc]

ADC:

 hadc1.Instance = ADC1;

  hadc1.Init.ClockPrescaler = ADC_CLOCK_ASYNC_DIV1;

  hadc1.Init.Resolution = ADC_RESOLUTION_14B;

  hadc1.Init.GainCompensation = 0;

  hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;

  hadc1.Init.ScanConvMode = ADC_SCAN_ENABLE;

  hadc1.Init.EOCSelection = ADC_EOC_SEQ_CONV;

  hadc1.Init.LowPowerAutoWait = DISABLE;

  hadc1.Init.ContinuousConvMode = DISABLE;

  hadc1.Init.NbrOfConversion = 2;

  hadc1.Init.DiscontinuousConvMode = DISABLE;

  hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;

  hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;

  hadc1.Init.DMAContinuousRequests = ENABLE;

  hadc1.Init.TriggerFrequencyMode = ADC_TRIGGER_FREQ_HIGH;

  hadc1.Init.Overrun = ADC_OVR_DATA_PRESERVED;

  hadc1.Init.LeftBitShift = ADC_LEFTBITSHIFT_NONE;

  hadc1.Init.ConversionDataManagement = ADC_CONVERSIONDATA_DMA_CIRCULAR;

  hadc1.Init.OversamplingMode = ENABLE;

  hadc1.Init.Oversampling.Ratio = 3;

  hadc1.Init.Oversampling.RightBitShift = ADC_RIGHTBITSHIFT_NONE;

  hadc1.Init.Oversampling.TriggeredMode = ADC_TRIGGEREDMODE_SINGLE_TRIGGER;

  hadc1.Init.Oversampling.OversamplingStopReset = ADC_REGOVERSAMPLING_CONTINUED_MODE;

  if (HAL_ADC_Init(&hadc1) != HAL_OK)

  {

    Error_Handler();

  }

  /** Configure Regular Channel

  */

  sConfig.Channel = ADC_CHANNEL_9;

  sConfig.Rank = ADC_REGULAR_RANK_1;

  sConfig.SamplingTime = ADC_SAMPLETIME_20CYCLES;

  sConfig.SingleDiff = ADC_SINGLE_ENDED;

  sConfig.OffsetNumber = ADC_OFFSET_NONE;

  sConfig.Offset = 0;

  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)

  {

    Error_Handler();

  }

  /** Configure Regular Channel

  */

  sConfig.Channel = ADC_CHANNEL_10;

  sConfig.Rank = ADC_REGULAR_RANK_2;

  if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)

  {

    Error_Handler();

  }

[Andrew Neil]

Please see the posting tips for how to properly post source code; also details needed - what board, etc:

https://community.st.com/t5/community-guidelines/how-to-write-your-question-to-maximize-your-chances-to-find-a/ta-p/575228

 

---

@lsc wrote:

When using a debugger, the sampled data is normal. However, when the device is running, the sampled data is not correct.

---

In what way, "not correct" ?

One key difference when running under debug is that the target probably doesn't actually enter the STOP mode...

[lsc]

Below is the ADC configuration. After being awakened from Stop 2 mode by the LPTimer, the ADC data sampling results are higher than expected

ADC:

 hadc1.Instance = ADC1;
 hadc1.Init.ClockPrescaler = ADC_CLOCK_ASYNC_DIV1;
 hadc1.Init.Resolution = ADC_RESOLUTION_14B;
 hadc1.Init.GainCompensation = 0;
 hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
 hadc1.Init.ScanConvMode = ADC_SCAN_ENABLE;
 hadc1.Init.EOCSelection = ADC_EOC_SEQ_CONV;
 hadc1.Init.LowPowerAutoWait = DISABLE;
 hadc1.Init.ContinuousConvMode = DISABLE;
 hadc1.Init.NbrOfConversion = 2;
 hadc1.Init.DiscontinuousConvMode = DISABLE;
 hadc1.Init.ExternalTrigConv = ADC_SOFTWARE_START;
 hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
 hadc1.Init.DMAContinuousRequests = ENABLE;
 hadc1.Init.TriggerFrequencyMode = ADC_TRIGGER_FREQ_HIGH;
 hadc1.Init.Overrun = ADC_OVR_DATA_PRESERVED;
 hadc1.Init.LeftBitShift = ADC_LEFTBITSHIFT_NONE;
 hadc1.Init.ConversionDataManagement = ADC_CONVERSIONDATA_DMA_CIRCULAR;
 hadc1.Init.OversamplingMode = ENABLE;
 hadc1.Init.Oversampling.Ratio = 3;
 hadc1.Init.Oversampling.RightBitShift = ADC_RIGHTBITSHIFT_NONE;
 hadc1.Init.Oversampling.TriggeredMode = ADC_TRIGGEREDMODE_SINGLE_TRIGGER;
 hadc1.Init.Oversampling.OversamplingStopReset = ADC_REGOVERSAMPLING_CONTINUED_MODE;
 if (HAL_ADC_Init(&hadc1) != HAL_OK)
 {
 Error_Handler();
 }

 /** Configure Regular Channel
 */
 sConfig.Channel = ADC_CHANNEL_9;
 sConfig.Rank = ADC_REGULAR_RANK_1;
 sConfig.SamplingTime = ADC_SAMPLETIME_20CYCLES;
 sConfig.SingleDiff = ADC_SINGLE_ENDED;
 sConfig.OffsetNumber = ADC_OFFSET_NONE;
 sConfig.Offset = 0;
 if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
 {
 Error_Handler();
 }

 /** Configure Regular Channel
 */
 sConfig.Channel = ADC_CHANNEL_10;
 sConfig.Rank = ADC_REGULAR_RANK_2;
 if (HAL_ADC_ConfigChannel(&hadc1, &sConfig) != HAL_OK)
 {
 Error_Handler();
 }