STM32F1: adc_channel_setup() fails with "Invalid channel reference" on valid DTS configuration

[eiten]

Describe the bug

The adc_channel_setup() function for the st,stm32f1-adc driver fails at runtime with the error message adc_stm32: Invalid channel reference. This happens even when the Device Tree configuration for the ADC channel is syntactically correct and complies with the driver's bindings (e.g., zephyr,reference = "ADC_REF_VDD_1";).

Regression

• This is a regression.

Steps to reproduce

Use this sample https://github.com/eiten/zephyr/tree/fix/stm32f1_adc_bug
Use a board with an STM32F103xB MCU.
Configure an ADC channel as a sub-node of &adc1 in the board's DTS file.
Call adc_channel_setup() for this channel in the application code.
The setup fails with error code -22 (EINVAL).

Relevant log output

*** Booting Zephyr OS build v4.1.0-5574-gb1ad7877f238 ***
[00:00:00.001,000] <inf> main2: Starting final ADC test...
[00:00:00.001,000] <err> adc_stm32: Invalid channel reference
[00:00:00.001,000] <err> main2: Failed to setup motor ADC channel 9 (-22)

Impact

Functional Limitation – Some features not working as expected, but system usable.

Environment

OS: Debian Bookworm
Toolchain: Zephyr SDK 0.17.1
Zephyr version: v4.1.0-5574-gb1ad7877f238

Additional Context

• The issue was debugged extensively. We confirmed that the ADC clock prescaler and acquisition time settings are correct.

• The problem can be worked around by completely skipping the adc_channel_setup() call and manually setting the required hardware registers (ADC_CR2->TSVREFE for internal channels and ADC_SMPR1/2 for acquisition time). This proves that the underlying adc_read() function and hardware are working correctly and the bug is isolated to the setup/validation logic within adc_channel_setup().

Workaround is attached.

workaround.zip

[github-actions]

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[JarmouniA]

Would be great if you can provide the DT overlay (or at the very least the ADC node), and attach your workaround as a git branch instead of a ZIP file.

[eiten]

I attached the DT file in the ZIP along with the main file.
How do I attach it as a git branch? Fork the project, clone it, init a new west workspace and add my files in which directory?

[JarmouniA]

I attached the DT file in the ZIP along with the main file. How do I attach it as a git branch? Fork the project, clone it, init a new west workspace and add my files in which directory?

An example app would suffice https://github.com/zephyrproject-rtos/example-application

[eiten]

I attached the DT file in the ZIP along with the main file. How do I attach it as a git branch? Fork the project, clone it, init a new west workspace and add my files in which directory?

An example app would suffice https://github.com/zephyrproject-rtos/example-application

Oh, I now made a fork and a pull request: #91964

I added the config and overlay for nucleo_f103rb

[JarmouniA]

You don't have to open a PR, the link to your branch is sufficient https://github.com/eiten/zephyr/tree/fix/stm32f1_adc_bug