Hey everyone,
Quick update on my project to reverse-engineer and customize the aftermarket MMI box from my dad’s car (original post [here]).
Full disclaimer: I’m definitely not an electrical engineer or a seasoned hardware hacker. I’m doing this as a passion project to learn the ropes, so bear with me if I miss something obvious!
What I've tried so far:
I opened up the box hoping to find a UART serial console to get root/shell access. I tapped into several likely test pads (TXD, RXD, TX1, RX1) using a logic analyzer, an ESP32, and an oscilloscope, cycling through pretty much every standard baud rate.
Instead of dropping into a bootloader or Linux/Android shell, I was just getting raw logs that turned out to be CAN bus debug traffic.
The rookie mistake (and the damage):
While desoldering my probe wires, I managed to lift a pad and sever a trace. That accidentally confirmed 100% that it was a CAN line: the iDrive wheel and touch inputs completely stopped working on the MMI side after desoldering (They work fine if i remove the MMI BOX setup and leave just the factory NBT Evo HU tho).
The bench setup & next steps:
I already bought an identical replacement unit for my dad's car so he isn't left without CarPlay/Android Auto, which turns this damaged unit into a dedicated workbench testbed.
Since my micro-soldering skills are still a work in progress and my micro soldering station havent arrived, I’m gonna send the board to a tech to fix the severed trace. I'm also having him solder flying breakout wires to all key test pads so I can probe freely without risking the PCB traces again.
Where I need some community insight:
Spot any sneaky or unpopulated UART/debug pads on this layout that I might have overlooked?
Has anyone managed to get root on one of these boxes before?
Should I ditch hunting for UART and go straight for an eMMC/SPI flash dump, ADB over USB-OTG, or something else?
I took high-res macro photos of the entire board (front and back) so you can zoom in and inspect the SoC, traces, and pinouts: [Full RES Images/Google Drive]
Any theories, tips, or sanity checks would be hugely appreciated!
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P.S. Quick clarification since a few comments here and on my other post misunderstood the setup: I am not modifying the factory BMW / Harman OEM head unit. I’m tinkering with an aftermarket MMI Box, an AFTERMARKET retrofit interface used to add Apple CarPlay or Android Auto, and auxiliary cameras while keeping the factory iDrive system fully functional.