Proper error handler

[kbeckmann]

Not sure how much energy we should spend on this but it kinda sucks to do

if (r != ERR_OK)
	while (1) ;

We don't need to do fancy ram dumping and so on, but just halt the cpu and perhaps disable interrupts and that we get a central point where we can set a breakpoint when debugging.

[arturo182]

It was just made like this because when I wrote it we had no UART support, now we could actually print to uart or do something else that's smart :P

[kbeckmann]

Ideally we should print it to the control cdc that hasn't been implemented yet.. :P

[arturo182]

It is now ;)

[arturo182]

If we implement the HID CLI mentioned in #44 then we could actually have ram dumping and then fetching over CLI. But we would need to use 64K of flash for the dump area.

[kbeckmann]

Think we can survive with an error handler that stalls the cpu and lets you attach with a debugger..

[arturo182]

Debugging a debugger :O

[EnJens]

we could have 'offline' semi-dumps where we just dump the absolutely minimum, say current PC of all threads, the last few lines of logs, just the bare minimum to get something useful. Wouldn't take many KB.

[arturo182]

we don't really have logs right now :P can't just print on the cdc cause can't know if that was log or dut uart