LPC5536 Debugging went wrong

[Bela1]

Ladies and Gentlemen,

I am trying to debug my own FW on my own target board with LPC5536JBD100. I do it since about two days with a newly purchased MCU LINK - PRO circuit.

Until today I only had problems with my own code. Today, suddenly, MCUXpresso doesn't recognize any SWD target. See the attached screenshot, please.

When I took another, still brand new board, I only could program it once, then I got the same message like in the screenshot.

I made a new, empty project, the code does nothing, it is automatically generated by MCUXpresso 11.9.0. My SDK version is 2.14.

With the oscilloscope, I saw signals on the SWDIO and on SWCLK lines. Haven't seen anything on the RESET and SWO lines. Reset is high, SWO is low.

What can I do, to get my board back again, to be able to program and debug?

What shall I take care of, to avoid such a situation?

[Bela1]

My next experience is:

This morning I took a brand new, never-seen-power board. Connected to the programmer by SWD debug cable. Power is coming from the debugger. The very first time I used MCUXpresso, and the code was automatically generated when I created a new project. Actually, this is a dummy code, does nothing. I could debug it, I single-step through the code. It was all right.

Then, I ended the debug session. Did nothing in the source code, it remained unchanged. Started the debug session again, and I got the same failure like above. The debugger doesn't see any SWD target anymore.

I also tried to keep the Reset button pressed, when switching to debug mode. Of course it didn't work, but I got another failure message than before.

What can be wrong? Can I get the access to my controller back?

[Alice_Yang · Accepted solution]

Hello @Bela1 

It is possible to download an wrong image into the flash on the target that will then prevent any further debug access or connections. Please enter ISP mode, then using Flash Magic or SEC tool to erase whole chip. For LPC5536,If we program an incorrect Image, or an illegal operation,  cannot debug. We need inter ISP mode to erase. Also can refer to: https://community.nxp.com/t5/LPCXpresso-IDE-FAQs/Regaining-debug-access-to-target-MCU/m-p/473923  

You can contact me if there is issue when using Flash Magic or SEC tool. 

BR

Alice

[Bela1]

Can I close myself out from the microcontroller by a wrong firmware? If yes, how? And what shalle I take care of, to avoid such a failure?