Backing up the display firmware / data is generally not needed as pretty much all the important information comes from the phone during use. There are some situations where it may be useful however.
The display itself is running Android 5.1 and as such follows a fairly standard Android filesystem structure
boot holds the system kernel and initial startup code
recovery is a separate bootup system to provide functionality for upgrading, wiping etc.
system holds the majority of the Android and Navdy code
data has the user data, including bluetooth pairing, locale, dash layout etc. This is wiped during a factory reset
maps this is the drive that's shown when plugging the display into computer as a usb flash driver, it is mainly used to hold map data.
On a pristine system from navdy, there's no known way to backup and of these partitions, other than copying files off the maps drive in usb mass storage mode.
Since my 3060 firmware pack however, I've started modifying the recovery partition to provide access to the entire unit when plugged into PC.
This process requires you to be able to plug your navdy into computer on USB while it's powered by car / 12V.
So you'll either need:
a laptop in your car
long usb repeater cable into house (may or may not work reliably)
Note: this process will replace the recovery partition with my modified one which has permissions to access the filesystems.
This will allow you to backup your boot, data and system partitions which are the more important ones for navdy use generally. The modifications only come into play if the navdy is plugged into computer on USB when rebooted into recovery mode. When not plugged into computer during recovery startup, it still works as a normal recovery system for factory resets, updates etc.
Plug a usb cable into the back of the navdy, but don't plug into computer yet.
Put the navdy into the car cradle / power supply and wait for it to start up normally.
Plug the USB cable into computer, you may or may not get a little popup saying device detected.
If running windows, run WIN_INSTALL_USB_DRIVER to install the Android ADB drivers.
Run FLASH_RECOVERY_WIN (if running windows) or FLASH_RECOVERY_OSX_LINUX (if running mac or linux) and wait for it to complete.
This will reboot into bootloader mode, install my recovery image, then boot into the modified recovery environment.
If you get stuck at "Rebooting to recovery, screen should stay black." for more than 10-20 seconds, check the light on the navdy hasn't come on green.
If it has, unplug the usb and remove from cradle, wait for light to go off, then start again. If it continues to happen get in touch on reddit or raise an issue on this project.
Once the FLASH_RECOVERY script is finished, the screen on the navdy should look blank but the light on the front should be white.
Run BACKUP_NAVDY_WIN or BACKUP_NAVDY_OSX_LINUX, this should copy the system, data and boot partitions to a file on the unit, then copy that file to the local folder on your computer.
Once that's finished, you can simply unplug the navdy from computer and car cradle, leave it off until the front light turns off, then put it back on the car cradle. It should boot up again in normal mode like nothing happened.
If the version of navdy you've backed up is not one of mine or the original navdy 3049 build, I'd be very interested in a copy of the boot and system partitions (only data has user information on it). Please do get in touch with me to let me know!