Both of my FRDM-K22F boards' debuggers are dead in the same way. Plug them into the USB port and nothing happens. The green light on the board doesn't go on. Windows 10 doesn't see a device.
They both died yesterday afternoon. I'd been using those boards for a couple of years.
So I got out my trusty J-Link and burned the OpenSDA bootloader into the debug processor via connector J12. J-Flash says it went in just fine. Still nothing. I tried both bootloader V2.1 and V2.2. The image of bootloader V2.1 is the exact same file I put into the two boards a couple of years ago.
I notice that the debug processor seems to be in some sort of fault loop. The reset line (TP15) goes high for 12us, low for 50us, and repeats. The logic low level is 0.6V. This is even with the J-Link disconnected from J12.
Any ideas about how I can get these boards working again?
I found the threads about adjusting the Windows 10 policies so that it doesn't attack the boards again, so they ought to stay alive if I can get them to live again.