Nucleo-H753ZI board Connect ADC inputs to GND, the readings are varied between -15 - +15

[RongShengWang]

Nucleo-H753ZI board. ADC1 configurations: INPUT: SINGLE-END

Sample clock rate = 5Mhz

Sample rate = 10Khz,

Sample Time = 16.5 cycles,

Resolution = 12-bit

Scan 256 times

Connect the defined two ADC input channels to GND.

The 256 readings FOR EACH INPUT are varied between (-15 - +15), more or less, while they should be read as zeros.

Question: Can it be fixed How to fix it?

Could you do the same test to confirm it?

Thanks,

Rong

[Chris21]

The lowest value a single-ended ADC channel can have is 0, how do you get negative numbers?

[RongShengWang]

Sorry, I pasted wrong data. It should be

5, 0, 5, 0, 12, 0, 15, 1, 0, 0, 0, 0, 3, 5, 17, 0, 0, 0, 0, 0, 0, 15, 0, 11, 17, 16, 0, 0, 12, 0, 4, 15, 7, 0, 0, 0, 0, 0, 0, 0, 5, 10,

Total 256's. I just listed first 40's.

Thanks

[Chris21]

Are you executing the calibration functions?

https://www.st.com/resource/en/application_note/an5354-getting-started-with-the-stm32h7-series-mcu-16bit-adc-stmicroelectronics.pdf

[RongShengWang]

5, 0, 5, 0, 12, 0, 15, 1, 0, 0, 0, 0, 3, 5, 17, 0, 0, 0, 0, 0, 0, 15, 0, 11, 17, 16, 0, 0, 12, 0, 4, 15, 7, 0, 0, 0, 0, 0, 0, 0, 5, 10, 14, 0, 0, 0, 4, 13, 0, 13, 0, 0, 0, 0, 1, 0, 0, 0, 0, 16, 8, 0, 16,12, 0, 13, 0, 0, 9, 0, 0, 0, 3, 0, 0, 15, 0, 0, 13, 0, 1, 16, 0, 0, 16, 9, 0, 0, 18, 0, 13, 0, 0, 0, 17, 0, 0, 0, 6, 0...}

[RongShengWang]

"Are you executing the calibration functions?"

Of course.

Data

5, 0, 5, 0, 12, 0, 15, 1, 0, 0, 0, 0, 3, 5, 17, 0, 0, 0, 0, 0, 0, 15, 0, 11, 17, 16, 0, 0, 12, 0, 4, 15, 7, 0, 0, 0, 0, 0, 0, 0, 5, 10, 14, 0, 0, 0, 4, 13, 0, 13, 0, 0, 0, 0, 1, 0, 0, 0, 0, 16, 8, 0, 16,12, 0, 13, 0, 0, 9, 0, 0, 0, 3, 0, 0, 15, 0, 0, 13, 0, 1, 16, 0, 0, 16, 9, 0, 0, 18, 0, 13, 0, 0, 0, 17, 0, 0, 0, 6, 0...}

[Karl Yamashita]

---

@RongShengWang wrote:

"Are you executing the calibration functions?"

Of course.

Data

5, 0, 5, 0, 12, 0, 15, 1, 0, 0, 0, 0, 3, 5, 17, 0, 0, 0, 0, 0, 0, 15, 0, 11, 17, 16, 0, 0, 12, 0, 4, 15, 7, 0, 0, 0, 0, 0, 0, 0, 5, 10, 14, 0, 0, 0, 4, 13, 0, 13, 0, 0, 0, 0, 1, 0, 0, 0, 0, 16, 8, 0, 16,12, 0, 13, 0, 0, 9, 0, 0, 0, 3, 0, 0, 15, 0, 0, 13, 0, 1, 16, 0, 0, 16, 9, 0, 0, 18, 0, 13, 0, 0, 0, 17, 0, 0, 0, 6, 0...}

---

And to be sure we're all on the same page, how are you exactly calibrating?

[RongShengWang]

" how are you exactly calibrating?"

if (HAL_ADCEx_Calibration_Start(&hadc1, ADC_CALIB_OFFSET_LINEARITY, ADC_SINGLE_ENDED) != HAL_OK)

  {

      Error_Handler();

  }

  if (HAL_ADCEx_Calibration_Start(&hadc2, ADC_CALIB_OFFSET_LINEARITY, ADC_SINGLE_ENDED) != HAL_OK)

  {

      Error_Handler();

  }

  if (HAL_ADCEx_Calibration_Start(&hadc3, ADC_CALIB_OFFSET_LINEARITY, ADC_SINGLE_ENDED) != HAL_OK)

  {

      Error_Handler();

  }

[Karl Yamashita]

You may need to try improving VDDA/VREFP filtering. You can also try enable oversampling.

[RongShengWang]

What is your experience? Or you just guess? I am using Nucleo-H753ZI board.