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3 years ago I built the first version of my navi retrofit for my Mazda based on a Raspberry Pi4, RPI Pico, CarPiHAT PRO and OpenAuto Pro. That system still works well in my car, but as software support stopped, I started looking for alternatives instead of putting more work in the development.

Here is a video of that system from 2023:
Mazda3 Stock Navi Retrofit - RPI4 + RPI Pico + OAP

I started developing a new system while the previous one is still in the car, so I bought a bunch of parts from various junkyards to have a separate dev system. First it was based on a Raspberry Pi 5 with a custom Android build, a short video of that test system:
Mazda3 Navi Retrofit V2 PoC - RPI5, Android 15, FullHD touchscreen

Later I moved the development to a Compute Module 5 with Hudiy, and the dev hardware stack at the moment looks like this:

- RPi Compute Module 5, 16 GB RAM, 64 GB storage
- Hailo 8 M.2 AI vision accelerator
- FullHD 7" navigation touch screen, replacing the old low res. non-touch LCD
- 1424 x 280 resolution 6.9" headunit screen, replacing the B/W low-res, text only screen.
- V-Link OBD adapter
- BTT U2C v2.1 USB-to-CAN Adapter
- Unihertz Jelly Star for Android Auto
- Mazda3 headunit
- Mazda3 navigation housing
- Sandberg HDMI Capture Link for real time image processing testing

The plan is to make a custom IO Board for the CM5, which will fit in the bottom of the stock Mazda headunit and will connect via the extension port, which is normally used by the tape deck, or MiniDisc player or MP3 player, depending on the trim level and model year.

Nice work!! Any audio setup planned?

wkl3968 wrote: Tue Mar 10, 2026 5:12 am Nice work!! Any audio setup planned?

Thank you! For now the audio is just routed through a simple USB sound card in the dev system, but that's just for the early testing purposes.

The simpler plan is to have a 192kHz/24bit Burr-Brown digital-to-analog converter or something similar on my custom IO board, like on the CarPiHat PRO, the other variation is, that I hack the headunit and directly inject digital audio into it, as it already has audio conversions in both directions, or I could build a custom amplifier with a high quality DAC inside the original headunit case. We'll see.

At the moment the car has the stock sound system with one addition, a set of Alpine SXE-1006TW tweeters, and the version in the car uses a CarPiHat PRO with a CD charger emulator.

Forgot to post this, the setup was assembled for one our events at work