MHI2Q CarPlay cluster integration

CarPlay patch set for Audi MHI2Q infotainment. (Based on MHI2Q firmware, but may need rebuild for different versions.)

Disclaimer: Use at your own risk. These patches modify firmware binaries and system configurations on your infotainment unit. Always back up all original files before making any changes. The authors are not responsible for any damage, bricked devices, or warranty issues resulting from use of these patches.

Gallery

Contents

• Gallery
• Features
• Repository layout
• Build
• Deployment
• Logging
• Documentation
• Known issues & TODO
• References

Features

What this patch makes the head unit + cluster do that stock MHI2Q doesn't:

• Full HUD route guidance from CarPlay nav (Maps, Waze, etc.) - maneuver icons, lanes, distance bargraph, ETA and destination.
• Custom maneuver overlay drawn over the cluster's native map plane (the same MOST video plane the HU uses for its own map), transparent when idle.
• Album cover art forwarded to the cluster's now-playing widget.
• MMI touchpad → DPAD bridging so finger drags navigate CarPlay menus.
• Steering-wheel roller - rotation keeps stock map zoom; the OK press toggles the cluster route-info readout (arrival time).

Repository layout

Raw unit logs and generated class trees are intentionally kept outside Git.

Build

Run from the repository root:

./scripts/build_java.sh        # → build/carplay_hook.jar
./scripts/build_hook.sh        # → build/libcarplay_hook.so
./scripts/build_renderers.sh   # → build/maneuver_render

All three build in Docker - no host toolchain required. The Java patch compiles in a pinned eclipse-temurin:8 container (against the stock jar + OSGi libs under ../../Tools/jxe2jar); the two native builds use the qnx65-armv7-toolchain image and synthesize their import stubs, so the resulting ELF binds the unit's real Screen/EGL/GLES libraries at runtime. There are no Java variants.

The hook logs by default. To adjust at build time:

./scripts/build_hook.sh                        # LOG=1, logging compiled in (default)
LOG=0 ./scripts/build_hook.sh                  # strip logging entirely
LOG_RGD_PACKET_RAW=1 ./scripts/build_hook.sh   # + raw RGD packet hex dumps (needs LOG=1)

Full toolchain, threading and boot details live in the knowledge base - see docs/architecture.md.

Deployment

Get a root shell on the unit (SSH), back up every file you touch, then just drop the files in place and reboot.

1. Copy the runtime files to /mnt/app/root/hooks/ (chmod +x the scripts):

2. Point the supervisor at them. In /mnt/system/etc/eso/production/smartphone_integrator.json, replace the children.carplay block with deploy/smartphone_integrator/carplay_child.json.

3. Register the route-guidance message IDs. In /mnt/system/etc/eso/production/dio_manager.json, add the RGD message IDs so the Cinemo iAP2 SDK actually pumps them (without this, iOS sends route guidance and the SDK silently drops it):

• MessagesSentByAccessory += "0x5200", "0x5203"
• MessagesReceivedFromDevice += "0x5201", "0x5202", "0x5204"

(The hook separately patches the outgoing Identify so iOS starts sending route guidance in the first place - both are required.)

4. Java patch. Copy build/carplay_hook.jar to /mnt/app/eso/hmi/lsd/jars/; the HMI loads it on the next start.

5. Reboot. Let the writes reach the flash first - run sync and give it a few seconds. A forced reboot (the MMI button combo) right after copying can leave the files truncated or gone entirely, and you will be left wondering why nothing loaded. On boot smartphone_integrator launches everything; check /tmp/carplay_hook.log and /tmp/carplay_java.log (see Logging).

Exact ownership rules, the LD_PRELOAD/env constraints and the MU1316 QNX-compat audit are in deploy/smartphone_integrator/README.md.

Logging

Both sides write to /tmp on the unit:

By default only warnings and errors are recorded. To capture everything (lift both hook and Java to INFO), drop a marker file on the unit - no rebuild, no restart of dio_manager needed:

touch /mnt/app/carplay_verbose        # or /tmp/carplay_verbose

Remove the marker to return to the quiet default. Logs reset on reboot, so pull them before restarting. For raw route-guidance packet dumps, rebuild the hook with LOG_RGD_PACKET_RAW=1 (see Build).

Documentation

docs/ is an Obsidian knowledge base - one note per topic, each fact validated against code / firmware / iOS binary. Start at docs/INDEX.md: architecture & threading, the hook and bus, route guidance (TLV → BAP → cluster), cluster compositing, input, deploy/connect, the reverse-engineering references, and a per-note verification status.

Known issues & TODO

Help wanted - open items on the current branch:

• Maneuver renderer has no lane guidance. The BAP HUD renders lane arrows, but the projection overlay (maneuver_render) does not. Lane data should be plumbed through to the renderer and drawn the same way the HUD does.
• Punch-through during the RGI on/off animation. While route guidance animates in or out, a hole to the stock map layer is briefly visible - the map backing (KDK 101/102) is drawn out of sync with the animation. Looks like a timing problem in the show/hide sequence; the backing and the animation need to be synchronised.
• Wrong icon for the ramp exit on the projection. Leaving a ramp draws a three-section arrow that doesn't match the maneuver. Likely an off-ramp mapping bug in ManeuverMapper - the projection descriptor for that case needs fixing.

Reporting a bad maneuver icon. The iAP2→BAP mapping covers all 54 CarPlay maneuver types but has only been exercised on a limited set of real routes. A snippet of /tmp/carplay_hook.log from the moment plus a note on what was expected helps a lot. The hook logs unrecognised route-guidance messages as [HOOK] Unknown 0x52xx msgid=0xNNNN dir=IN len=N followed by a hex dump - that line is the best starting point when iOS sends a maneuver type we don't handle yet.

References

Thanks for the prior work and knowledge that helped figure this out.

• https://github.com/ludwig-v/wireless-carplay-dongle-reverse-engineering
• https://github.com/EthanArbuckle/iPhone18-3_26.1_23B85_Restore
• https://github.com/adi961/mib2-android-auto-vc
• @fifthBro

---

_{What are you doing all the way down here? There's nothing to see…}

…or is there?

🚀 Coming soon. Maybe. Someday. No promises.

It was just the warm-up, next:

• AltScreen - full CarPlay map, right in cluster
• Multichannel audio support - from stereo up to 6- or even 8-channel
• Apple Spatial Audio
• Dolby Atmos - High Quality 5.1.2 masters
• Video playback - an Apple TV on wheels

Stay tuned. 👀