Update... Fixed the old unit by re-flashing the firmware.
A friend of mine was able to rig up a level shift chip and a USB-to-serial adapter and was able to talk to my old MMI unit through the diagnostic port on the 5F logic board. Once hooked up to a terminal program - the boot sequence showed some errors about not being able to reach /usr/sbin and gave checksum errors on the file system (The internal flash memory (OS) - not the HDD (jukebox and map/etc)).
More or less following the guide here : https://www.scribd.com/doc/225614389/How-to-recover-a-bricked-Audi-MMI-3G-or-3G-Plus he was able to re-flash the OS partitions from a copy on the SD card.
Result : Old unit works great again. No component protection, and I have sound again.
Thought I'd post this for future reference. I had seen the "how to recover" guide previously but didn't think it would apply to this situation since I hadn't been upgrading or changing the firmware when it failed. Turns out the flash memory somehow got corrupted on it's own. Re-flashing solved my problem.
A friend of mine was able to rig up a level shift chip and a USB-to-serial adapter and was able to talk to my old MMI unit through the diagnostic port on the 5F logic board. Once hooked up to a terminal program - the boot sequence showed some errors about not being able to reach /usr/sbin and gave checksum errors on the file system (The internal flash memory (OS) - not the HDD (jukebox and map/etc)).
More or less following the guide here : https://www.scribd.com/doc/225614389/How-to-recover-a-bricked-Audi-MMI-3G-or-3G-Plus he was able to re-flash the OS partitions from a copy on the SD card.
Result : Old unit works great again. No component protection, and I have sound again.
Thought I'd post this for future reference. I had seen the "how to recover" guide previously but didn't think it would apply to this situation since I hadn't been upgrading or changing the firmware when it failed. Turns out the flash memory somehow got corrupted on it's own. Re-flashing solved my problem.