The NXP MCU-Link Pro debug probe includes a LPC804 as an additional microcontroller on the board, including its debug header.
The question is: how to debug the on-board extra LPC804 microcontroller with an external debug probe?
One easy way to debug the LPC804 is to use the MCU-Link Pro debug probe for it, simply connecting the MCU-Link Pro Debug cable with the debug header of the LPC804:
That works and would be the recommended way. However, it seems that if using an external debug probe seems not always to work correctly (failed flash programming, source files not shown correctly). This did happen for some MCU-Link Pro boards, but not for others, and it was not always reproducible. So the reasons are not really clear to me, but I suspect that the LPC55S69 has some kind of impact if it is not ‘used’, as it always worked with using the LC55S59 as debug probe, either as a J-Link or as a LinkServer.
In any case, if you face the same problem: The solution we have found is to install the ‘FW Update Jumper’:
This keeps the LPC55S69 in bootloader/ISP mode, and it won’t interfere with the LPC804. That way no problems seen to use an external debug probe like a SEGGER J-Link or P&E Multilink for the LPC804:
With this I hope you find this post useful, if facing the same problem.
Happy debugging 🙂