Getting inaccurate value of ADC of STM32F030R8T6

[Chetan_1234]

Hello,
I am working on STM32F030R8T6 with HAL.

We are trying to read ADC values from the 4 ADC channels and 5th channel as VREFINT.
The ADC is configured in continuous DMA read by using:
HAL_ADC_Start_DMA(&hadc, (uint32_t *)ADC_Buffer, 5);
Our AVDD = 3.3 thus giving us resolution of 0.805mV for 12bit configuration.

My problem is that we are getting wrong values for the given input voltage.
and for VrefInt as well we are getting value of 1706, which seems quite high.

Can someone please guide me where can I go wrong?

[TDK]

• Are other channels accurate?
• How confident are you that VREF+ = 3.3V?
• What is the VREFINT_CAL value?
• Do a single channel conversion on VREFINT to eliminate potential sources of error.

[Chetan_1234]

1) No, other channels are also giving incorrect values.

2) Yes, we did a thorough inspection.

3) It falls between 1470 and 1704 in the range.

4) I'll give this solution a shot.

and the software resolution that we are providing is 0.853.

The system's output is shown in the table below.

Actual I/p Voltage	After calculation
A1	A2	A3	A4
3.28	3.207	3.228	3.229	3.239
5.15	5.172	5.234	5.235	5.242
12.95	13.510	13.614	13.605	13.607

[AScha.3]

Hi,

Did you run calibration first ?

(  HAL_ADCEx_Calibration_Start(&hadcxxx); )

[Chetan_1234]

I appreciate your advise and will give it a try.

[TDK]

> 3) It falls between 1470 and 1704 in the range.

That's a very wide range. I would suspect something is wrong with your hardware. Perhaps the rail is not stable.

(Calibrating before using is also required as pointed out.)