Quote Originally Posted by bartolfax View Post
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No matter: for 20$, I bought an used Drive 40, with screen damaged: it may possible that, from 2 broken devices I obtain a working Drive (if I'm lucky)
That's a good score. As far as I know there is only one screen type for Drive 40 so a screen swap to the $20 device should be fine. Assuming that it's otherwise undamaged of course. It's surprising how many devices with smashed or cracked screen also are 'bricked'. Ppl seem to either crack them using too much force trying to access preboot or abuse them in anger because they can't get them to boot up.

Question 1: they are utility and documentation about jtag programming of Garmin device?
Not that I'm aware of. Garmin would never distribute that information. There's been attempts by advanced users but nothing was ever published about successful results if there were any.

Question 2: is possible to connect a serial TTL i/f on the PCB to see something that is not a stupid message different from "SYSTEM SOFTWARE MISSING"?
Sorry, that's way above my pay-grade. Maybe someone can do it but ppl do sometimes keep their secrets close.