nRF52810 TX waveform anomaly

[Ryan.D.Zhang]

Hi all

   Recently, I have been developing a BT module using nRF52810. However, the module couldn't communicate normally with STM32 via UART as the MCU keep rebooting. And I tested the TX waveform with an oscilloscope, it turned out the voltage is abnormal at the begining in a couple of hundred milisecond. For detail，see the attached picture。The inside part of the

blue circle is the unexpected outcome of TX waveform，the normal voltage of tx should be about 3.3V

 

   Have you met the similar problem before, would you please give me some advice to solve this anomaly？ I really appreciate it..

 

[Andreas]

Hi,

 

Could this be due to a framing error when the UART is enabled? You either have to ignore this or enable the internal pull on the RX pin.

 

Best regards,

Andreas

[Ryan.D.Zhang]

Thanks, It's not like the frameing error. We found out this problem on bluetooth module after cutting off the communication with MCU. So I believe this problem is either related to the BT code or power noise interference in hardware.