Duplicate/out-of-sequence characters emitted by UART in J-Link OB-STM32F072-128KB-CortexM device

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    • Duplicate/out-of-sequence characters emitted by UART in J-Link OB-STM32F072-128KB-CortexM device

      Hello, I am using a J-Link OB-STM32F072 (part of the DWM1001-DEV board) and I am experiencing frequent corruption in data sent from the PC to the target through JLink's UART.

      In particular, I am using the serial line (on Linux, 115200 8N1) to interact with a ChibiOS shell running on a nRF MCU. Text transmitted by the PC often gets corrupted, with swapped or duplicated characters, usually at the beginning of a line.

      For example, in the attached USB trace (usb-eecho.pcapng), the "echo" command was received by ChibiOS as "eecho". I am also attaching a simple python3 script to reproduce the issue and an higher-level trace. It doesn't occur every single time, but the issue usually appears within less than 1 second.

      According to my tests, the issue occurs only if the PC transmits while the target MCU is also transmitting (please refer to the python script for the exact details). I have confirmed that the corruption is not simply a ChibiOS bug by connecting an independent UART receiver as a probe, which also received the same wrong data.

      Is this a known issue with a workaround?
      Thanks in advance,

      Fabio
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