xcertplay

Features

• CarPlay host applications for Android and Android Automotive OS.
• Support for MFI chips connected through a CH341 bridge or native /dev/i2c-N devices, local certificate/private-key files, and Remote MFI authentication (see the API below).
• Wired and wireless CarPlay connections.
• CarPlay Ultra triggering (the protocol stack is untested/incomplete, but it can trigger the CarPlay Ultra prompt on an iPhone).
• Voice, navigation, and music multi-channel audio output mapped to the corresponding Android channels.
• Dynamic Activity resizing with automatic re-handshaking to the new resolution.
• Separate web pages for the main and instrument displays (the browser decodes H.264/H.265 directly; the main display supports touch and audio).
• Vehicle head-unit location reporting.
• Android 9 (API 28) support.

Usage

1. Pair your iPhone with the head unit via Bluetooth.
2. Before a CarPlay video stream starts, tap the Settings button in the lower-right corner. You can also swipe down with three fingers to open Settings.
3. Make sure all the settings are configured as desired. To enable another entry gesture, turn on More gestures to Settings page. Start with one finger in the upper quarter of the left eighth of the screen, slide down along that strip, and lift in the lower quarter.
4. Scroll to the bottom and select Save & Reconnect.
5. Connect your MFi chip using the method you selected.
6. Wait for the connection to complete, then enjoy.

Web displays

1. In Settings, under Web displays, enable Main display and/or Instrument display, set the resolution, then tap Save & Reconnect.
2. Put the browser device on the same LAN as the Android device and open the address shown in Settings (https://<IP>:8080/main or /cluster; it can be copied). An open page stays connected while CarPlay reconnects and resumes by itself.
3. The certificate is self-signed: each browser warns once, choose to continue.
4. Main display page: touch with up to two fingers; while it is open the phone’s audio plays in the page. Tap the screen once to turn on sound (a browser requirement). The microphone stays on Android.
5. The instrument display page is view-only and needs the iPhone to provide the second display stream.

Use a recent Chrome, Edge, or Safari. If the browser cannot play H.265, turn off HEVC (H.265) in Settings.

Current progress

It works 👍. It has been tested on car head units and phones. If you encounter an incompatible car head unit, please open an issue and attach your log from /sdcard/Android/data/com.shilapi.xcertplay/files/logs/xcertplay.log.

Adapter board: CH341-to-MFI

Local MFI files

Choose Local files under MFI certificate & signing target, then use the two Choose buttons to select the certificate and private key with Android’s system document picker. The supported formats are a DER PKCS#7 certificate (.p7b) and its matching, unencrypted DER PKCS#8 private key (.pk8). The app validates that the files match before starting the phone connection and reloads them on MFI reconnect.

Store the private key in a protected location. Neither file is copied into app preferences; only Android’s persistent read permission and document URI are saved.

Project structure

Path	Purpose
common/	Shared CarPlay host activity, settings UI, persistence, and app resources used by both targets.
mobile/	Standard Android target using the shared CarPlay host UI.
automotive/	Android Automotive OS target with the shared host UI and advanced audio channel mapping.
shared/	Car App Library code plus the CH341, I2C, MFi, iPhone, iAP2, NCM, VPN, AirPlay, and media implementations.

Remote MFI

The Remote MFi client treats a remote service as an MFi chip for remote calls, or uses BAA authentication. Remote authentication avoids the process of connecting to a local MFi chip for authentication.

Endpoints

Method	Path	Purpose	Request body	Success response	Failure response
GET	/mfi/certificate	Get the MFi chip version, certificate type, and certificate contents; cached by the client after the first call	None	Certificate JSON	{"detail":"..."}
POST	/mfi/sign	Sign the challenge	{"challenge":"...","requestId":"..."}	{"signature":"..."}	{"detail":"..."}
POST	/mfi/reset	Request a reset of the remote MFi chip	{}	{"detail":""}	{"detail":"..."}

(Optional) Standard Bearer Authentication can be used for verification.

Currently, only BAA Authentication has been tested.

Requirements

• JDK 17 or newer to launch Gradle. The daemon resolves Java 25 through the Gradle toolchain.
• Android SDK Platform 37.
• Android 9 (API 28) or newer. On Android 9, Wi-Fi P2P 5 GHz mode is unavailable and LocalOnlyHotspot is used instead.
• Android NDK 28.2.13676358.
• A physical USB Host/OTG Android device and MFi hardware are required for hardware validation.

Build

On Windows PowerShell:

$env:JAVA_HOME = "C:\Program Files\Android\Android Studio\jbr"
.\gradlew.bat :shared:testDebugUnitTest :common:lintDebug :mobile:lintDebug :automotive:lintDebug :mobile:assembleDebug :automotive:assembleDebug

On macOS or Linux:

./gradlew :shared:testDebugUnitTest :common:lintDebug :mobile:lintDebug :automotive:lintDebug :mobile:assembleDebug :automotive:assembleDebug

Unsigned release APKs:

.\gradlew.bat :mobile:assembleRelease :automotive:assembleRelease

Acknowledgements

Thanks to LIVI for providing important reference for this project. Thanks to the showcase project for providing important reference for the BAA authentication in this project.

License

Licensed under the GNU General Public License v3.0.