Capacitive Touch Sensing on STM32U083RCT6 (PB5, PB6, PB7)

[Sakthi_IND]

Hi All,

We are currently working with the STM32U083RCT6 microcontroller for a capacitive touch switch and LED drive design. While all other functions are working correctly, we are encountering issues with the touch sensing functionality on pins PB5, PB6, and PB7.

Here are the details of our setup and the issue:

• Capacitive Sensing Pins: PB5 (Pin 57), PB6 (Pin 58), and PB7 (Pin 59) are configured for capacitive touch sensing.
• Touch Pad: A capacitive touch pad is placed between these pins. We have used a 1kΩ resistor as part of the design, but the touch sensing does not seem to respond correctly.
• Other Functions: All other functions, including LED driving and general I/O operations, are functioning properly.

Could you kindly provide guidance on the following points:

1. Pin Functionality: Are PB5, PB6, and PB7 suitable for capacitive touch sensing on the STM32U083RCT6? If not, could you suggest the appropriate pins for this purpose?
2. Resistor Value: We are currently using a 1kΩ resistor. Is this value appropriate, or should it be adjusted (e.g., using a 10kΩ to 100kΩ resistor) to improve touch sensing performance?
3. Touch Sensing Configuration: Are there specific settings or parameters that we should consider in our schematic or firmware (e.g., threshold values, debounce time, or calibration) to optimize the capacitive touch functionality?
4. Schematic Improvement: If there are any recommendations for improving our schematic to ensure reliable touch sensing, especially concerning pin connections, capacitive pad design, or other components, we would greatly appreciate your advice.
5. Software Settings: Any tips on ensuring that the STM32CubeMX settings and HAL libraries are correctly configured for capacitive sensing would be helpful.

We have verified the capacitive pad design, and environmental factors (such as grounding, shielding, and power supply quality) seem fine. Still, we are struggling with getting a reliable touch response.

We appreciate your time and assistance resolving this issue and look forward to your expert guidance.

[TDK]

Getting started with touch sensing control on STM32 MCUs - Application note

[Sakthi_IND]

Hi Guru,

Thank you for your previous response. We have followed the guidelines provided in the application note "Getting Started with Touch Sensing Control on STM32 MCUs" as suggested. However, we are still facing issues with the touch sensing functionality not working as expected.

Could you please advise if there are any additional software configurations required? Also, should we be making any changes to the circuit or hardware setup?

Any insights or suggestions you could provide would be greatly appreciated.

 

Regards,

Sathiya