RTT Autodetect works with J-Link RTT Viewer, but for pylink I have to explicitly provide the address

[NOhs]

Hello there,

I have a little cortex-M33 chip to which I connect using J-Link (V7.86h, but also tested V7.5). Using the J-Link RTT viewer and the following settings: I can connect to my device and read out the text it prints to the channel 0 buffer.

If I use the pylink example from this repo:

def main(target_device, block_address=None):
    """Creates an interactive terminal to the target via RTT.
    The main loop opens a connection to the JLink, and then connects
    to the target device. RTT is started, the number of buffers is presented,
    and then two worker threads are spawned: one for read, and one for write.
    The main loops sleeps until the JLink is either disconnected or the
    user hits ctrl-c.
    Args:
      target_device (string): The target CPU to connect to.
      block_address (int): optional address pointing to start of RTT block.
    Returns:
      Always returns ``0`` or a JLinkException.
    Raises:
      JLinkException on error.
    """
    jlink = pylink.JLink()
    print("connecting to JLink...")
    jlink.open()
    print("connecting to %s..." % target_device)
    jlink.set_tif(pylink.enums.JLinkInterfaces.SWD)
    jlink.connect(target_device)
    print("connected, starting RTT...")
    jlink.rtt_start(block_address)

    while True:
        try:
            num_up = jlink.rtt_get_num_up_buffers()
            num_down = jlink.rtt_get_num_down_buffers()
            print("RTT started, %d up bufs, %d down bufs." % (num_up, num_down))
            break
        except pylink.errors.JLinkRTTException:
            time.sleep(0.1)

It hangs in the while loop unless I explicitly provide the block_address.

Note:

• I am using pylink-square 0.14.3.
• The actual address of the buffer is: 0x20180f0c

Am I missing something else to get auto-detection to work in pylink-square?

Thank you for any tips or pointers that could help me getting auto-detect to work on my side.

[NOhs]

For anybody having the same issue: My mistake was to pass the target_chip_name instead of the full target_name to connect(...).

From the Segger wiki:

For Auto-Detection to work, J-Link needs to be passed the correct target device name (the target core name alone is NOT sufficient for Auto-detection)