ADC just giving raw value of 4095 on all channels

[harshpanchal_6]

Hello Community,

I’m working on a custom board using the STM32G474VET3 MCU and encountering an issue with the ADC readings. I’m consistently getting a raw value of 4095 on all the ADC channels I’m using. It seems like something might be misconfigured, but I haven’t been able to pinpoint the cause.

Any insights or suggestions would be greatly appreciated.

Thank you!

[Hl_st]

Hello,

can you please share your ADC settings.

[Ozone]

If you talk about the "usual" 12-bit successive-approximation ADC most STM32 implement, notice the value.
This 4095 is the maximal possible value, so it looks like the input voltage exceeds the range.

Post the relevant init code, and details about attached circuitry and voltages applied to the ADC inputs.

[Andrew Neil]

As the others have said, you need to give more details - please see How to write your question to maximize your chances to find a solution.

In particular, please post your code (see How to insert source code) & the schematics of this "custom board".

Have you checked at the STM32 pins that your ADC inputs are actually getting good signals?

Have you looked at ST's examples?

Have you tried this on a known-good ST board?

You still haven't marked the solutions to your previous threads.

[harshpanchal_6]

Sure

 

  

[harshpanchal_6]

static void MX_ADC3_Init(void)
{

  /* USER CODE BEGIN ADC3_Init 0 */

  /* USER CODE END ADC3_Init 0 */

  ADC_MultiModeTypeDef multimode = {0};
  ADC_ChannelConfTypeDef sConfig = {0};

  /* USER CODE BEGIN ADC3_Init 1 */

  /* USER CODE END ADC3_Init 1 */

  /** Common config
  */
  hadc3.Instance = ADC3;
  hadc3.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV2;
  hadc3.Init.Resolution = ADC_RESOLUTION_12B;
  hadc3.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc3.Init.GainCompensation = 0;
  hadc3.Init.ScanConvMode = ADC_SCAN_DISABLE;
  hadc3.Init.EOCSelection = ADC_EOC_SINGLE_CONV;
  hadc3.Init.LowPowerAutoWait = DISABLE;
  hadc3.Init.ContinuousConvMode = DISABLE;
  hadc3.Init.NbrOfConversion = 1;
  hadc3.Init.DiscontinuousConvMode = DISABLE;
  hadc3.Init.ExternalTrigConv = ADC_SOFTWARE_START;
  hadc3.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
  hadc3.Init.DMAContinuousRequests = DISABLE;
  hadc3.Init.Overrun = ADC_OVR_DATA_PRESERVED;
  hadc3.Init.OversamplingMode = DISABLE;
  if (HAL_ADC_Init(&hadc3) != HAL_OK)
  {
    Error_Handler();
  }

  /** Configure the ADC multi-mode
  */
  multimode.Mode = ADC_MODE_INDEPENDENT;
  if (HAL_ADCEx_MultiModeConfigChannel(&hadc3, &multimode) != HAL_OK)
  {
    Error_Handler();
  }

  /** Configure Regular Channel
  */
  sConfig.Channel = ADC_CHANNEL_10;
  sConfig.Rank = ADC_REGULAR_RANK_1;
  sConfig.SamplingTime = ADC_SAMPLETIME_2CYCLES_5;
  sConfig.SingleDiff = ADC_SINGLE_ENDED;
  sConfig.OffsetNumber = ADC_OFFSET_NONE;
  sConfig.Offset = 0;
  if (HAL_ADC_ConfigChannel(&hadc3, &sConfig) != HAL_OK)
  {
    Error_Handler();
  }
  /* USER CODE BEGIN ADC3_Init 2 */

  /* USER CODE END ADC3_Init 2 */

}

[harshpanchal_6]

 

[Andrew Neil]

That doesn't show the STM32.

Also, you said "all the ADC channels I’m using"; that shows two - are there any others?

Have you probed the signals at the STM32 pins? 

[Hl_st]

The configuration seems to me OK. Can you share also the code where is used ADC and read raw ADC value? 

Is it possible to test ADC on any unconnected MCU pin to know if there is problem in HW or in FW?

[Ozone]

Nice, but ...

Validate software functionality step by step, independant from other components (like external hardware).
"Integration tests" come later.

I suggest to connect a potentiometer to V(dda) and GND (or V(ref) if it's different from Vdda), and the wiper contact to the ADC input. Observe the ADC output values, add instrumentation code if necessary.
The values should follow from 0 to 4095, corresponding to a 0 ... V(ref) input.

The 3.6V Z-diodes are a good idea.