Thread: Garmin eTREX 20 working as an eTREX 30

Wait.... isn't it enough to delete GCD files of the same firmware version? Just don't patch BNE at 0x80113B6A and maybe that's it? I think it's necessary to delete GCD files, because no one else is going to delete them. And you can't delete GCD file you want to flash because it's not firmware who flashes it, the firmware only passes control to boot.bin from the GCD file. So you can delete the GCD file only after it has been flashed. This is why BNE at 0x80113B6A is absolutely necessary and shouldn't be patched.

UPD:
I think that if you really want to flash any GCD file flawlessly, then you need to:
1) set firmware version in the GCD headers to be as high as possible (99.99 is good enough )
2) patch boot.bin inside GCD file to delete the GCD file after flashing.
This method is better because no patches are required in the old firmware. And you don't have to deal with GUI code when patching new devices. But boot.bin patch is probably tricky, as you need to add a new function call.