Hi, I have the very same problem (bricked Xenon) and am unable to get it up and running. The challenge is that I have a Black Magic Probe debugger that is not OpenOCD compliant. Therefore I cannot use the description in the FAQ or in this thread.
I have done the following steps:
So what I see is that none if the LEDs are lit after reset, the PC is not recognizing the device as USB periferal, and when I attach the debugger to Xenon I see that the program counter is in the softdevice memory area. When I set a breakpoint to 0xf4240, that is the first executable code of the boot loader then I see that this breakpoint is never hit.
Is there anything that I miss? Alternatively can someone please send me a full Flash dump of a working Xenon that includes both the Code Flash and the UICR Flash ranges?
Update: Eventually I got it working.
As of the writing of this post, the latest firmware is v 1.4.4. This has got my Xenon unbricked:
This combo got the device up to a certain state from which I could individually update the middleware components via USB. In case of the boot loader I had to use --force-update, because, I think, the BL has identified itself more up to date than the release binary.
The major issue was the softdevice. I suspect that the binary file in the github release folder has been adjusted (?) for the particle update process. For example it has a strange stack pointer value at address 0x0000. The original softdevice 6.1.1 from the SDK has saved the day.