This page details common errors people run into while using PyLink. These errors do not mean the library is not working as intended, but rather a fault on the user end. If you cannot solve your issue by following any of the steps below, feel free to reach out.

Unspecified Error

If you ever see something similar to the following:

Traceback (most recent call last):
  File "pylink/", line 38, in async_wrapper
    return func(*args, **kwargs)
  File "pylink/", line 256, in open
    raise JLinkException(result)
__main__.JLinkException: Unspecified error.

Then congratulations, you’ve run into a catch-all error. This is a limitation imposed by native C SDK in which there is a catch-all error case. There are a couple possible solutions to this, and they are detailed below.

Unspecified Error during open()

If you see the unspecified error during open(), it means that one of the following is true:

  • Your J-Link is not connected to your computer.
  • Your J-Link is connected to your computer, but is currently held open by another application.

Unspecified Error during connect()

If you see the unspecified error during connect(), it means that any of the following is not true:

  • The target device’s chip name you passed to connect() is not the chip name of the actual target.
  • You’re trying to connect to the target over JTAG when it only supports SWD.
  • You’re trying to connect to the target, but the target is not plugged in.
  • You’re trying to connect to the target using a J-Link that does not have the target plugged in under its “Target” port.
  • The connection speed is bad (try 'auto' instead).

Unspecified Error during erase()

If you see the unspecified error during erase(), it means that your device is not properly halted. IF you’re using a Cortex-M device, try setting the reset strategy to JLinkResetStrategyCortexM3.RESETPIN to avoid your device’s application running when the system is booted; this is particularly useful if your application launches the watchdog or another service which would interpret the J-Link when erasing.

Unspecified Error during flash()

If you see the unspecified error during flash(), it means that either:

  • Your device is not properly halt. While flash() attempts to halt the CPU, it cannot if the device is breakpointed or similar.
  • The device is locked, in which case you have to unlock the device first.

Unspecified Error in Coresight

If you see an unspecified error while using a Coresight method, it means that you are trying to read from / write to an invalid register.