Document behaviour after successful modification or common unsuccesful modification

[freemin7]

If one follows this guide https://docs.google.com/document/d/1ZLD2jC9SxiCBk1NZLw667Tu3JuIk6PAyAxSHW7cWvu8/ one can not be certain whether the modification of the teensy4.1 was successful (or one cut into deeper layers).

There is also no indication whether an JTAG adapter is required if one wants to use a modified Teensy and whether flashing with USB using the default boot loader is still supported.

These would make a great addition either to the guide or the Readme.

Background:

I first wanted to modify a teensy and order the parts if my modification was successful. My teensy now shows the blink code: 2 Blinks = NXP JTAG Not Responding[1] and seems indifferent to presses if the reset button.

[1] See under heading Troubleshooting & Diagnostic Blink Codes

[freemin7]

Consulting with a person which also performed the modification i learned:

My teensy now shows the blink code: 2 Blinks = NXP JTAG Not Responding

That is normal behavior. When the JTAG lines are cut the boot loader chip can no longer talk to the SOC so the boot loader code flashes the LED. Once the JTAG lines are cut USB flash programming will no longer work. The Teensy will always need to be flashed via JTAG. Unless of course you re-solder the traces but then JTAG debug will not work.

This obvious but also undocumented.