[SOLVED] Are their serial limitations due to the internal buffer size w.r.t. the JLink VCOM?

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  • [SOLVED] Are their serial limitations due to the internal buffer size w.r.t. the JLink VCOM?

    Hi,

    This issue seems to be due to the JLink: github.com/pyserial/pyserial/issues/563

    It looks like if you send a buffer that is larger than a particular size through UART over the JLink (towards a nRF52 dev. kit), the receiving side gets garbage (starting with `USB`):

    Source Code

    1. import serial
    2. import time
    3. ser = serial.Serial(port="/dev/ttyACM0", baudrate=115200)
    4. print(ser.portstr)
    5. a=range(0,65)
    6. def send(data):
    7. print(data)
    8. ser.write(data)
    9. def sendInChunks(data, chunkSize=64):
    10. while len(data) > 0:
    11. d = data[0:chunkSize]
    12. print(d)
    13. ser.write(d)
    14. data = data[chunkSize:]
    15. send(a)
    16. #sendInChunks(a)
    17. ser.close()
    Display All
    See the linked issue for more details.

    Of course, we don't want to start using additional pins for hardware flow control. What are the limitations of the JLink? What's the size of the buffer used internally?

    wiki.segger.com/J-Link_Virtual_COM_Port doesn't have much in-depth info, so anything more would be appreciated.
  • Hi,
    Thank you for your inquiry.

    64 Bytes should not be a problem.
    Please note that support for on board J-Link (OBs) is provided by the
    evaluation board manufacturer and not by SEGGER.
    In case of the Devkit this would be Nordic.

    Best regards,
    Fabian
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