ADC giving value of 4095 on all configured channel

shafin388 · ‎2026-05-21

Hello Community,

I am working on a custom board using the STM32 MCU (STM32WLE5JCI6). I am configuring the ADC with two channels:

PB1 → ADC_IN5
PB3 → ADC_IN2

I performed the following test cases and observed unexpected ADC behavior.

Test Case 1

Applied VDD+ to Channel 2 (ADC_IN2)
Channel 5 (ADC_IN5) connected to GND

Observation:
Both ADC channels are reading 4095, even though Channel 5 is tied to GND.

Test Case 2

Applied VDD+ to Channel 5 (ADC_IN5)

Observation:
Instead of getting 4095 on Channel 5, both channels are reading approximately 1500.

I am also facing the same issue with another MCU: STM32L071KBT6TR.

Development tools being used:

STM32CubeIDE Version 2.1.0
STM32CubeMX Version 6.8.0

I have attached the main source file containing the ADC configuration for reference.

Could anyone please help identify what might be causing this issue?

Awaiting your valuable suggestions.

Thanks.

Andrew Neil · ‎2026-05-21

Welcome to the forum.

@shafin388 wrote:
I am working on a custom board

In that case, you need to post the schematic - see:

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