# Compatibility

This public preview is an independent receiver, not an Apple-certified CarPlay accessory. The experimental bundled accessory identity is extractable and its future acceptance is not guaranteed.

| Area | Current scope |
| --- | --- |
| Head unit | Upstream's official APK targets Android 9+. This local legacy fork has an API 19 installation floor and KitKat-specific implementations; this is not a verified hardware support list. See the T3 validation record below. |
| Phone | Standard, non-jailbroken iPhone with CarPlay enabled; device/iOS compatibility varies |
| Physical evidence | Previous private builds: wired and wireless picture, touch and audio confirmed on the development car with iPhone XS / iOS 18.7.10 |
| Other cars | Mixed community reports across DiLink generations; not a certified model support list |
| 0.2.14 evidence | Automated source/build validation and attributed contributor tests; no new complete-release vehicle test or universal model support is claimed. Earlier DiLink5.1 HUD/hotspot results remain historical evidence. |
| Wi-Fi | Auto uses eligible saved/aligned channels; beside a 5 GHz station, explicit 2.4 GHz precedes other 5 GHz/unpinned default fallbacks. Manual channels stay explicit; no band/performance guarantee. |
| Video | Default H.264 / 30 fps; 60 fps and HEVC increase device-specific demands |

## Legacy Android transport matrix

| Android version | Wired USB | Manual car hotspot | LocalOnlyHotspot | Wi-Fi Direct group |
| --- | --- | --- | --- | --- |
| 4.4 (API 19) | Raw configuration/alternate descriptors + authorized usbfs backend | Legacy interface discovery | Platform unavailable | System-generated group, firmware-dependent; no configurable group API |
| 5–7 (API 21–25) | Framework USB backend | Legacy interface discovery | Platform unavailable | Legacy group backend, firmware-dependent |
| 8–9 (API 26–28) | Framework USB backend | Yes | Yes | Legacy group backend; Android 8 can fall back to LocalOnlyHotspot |
| 10+ (API 29+) | Framework USB backend | Yes | Yes | Yes |

The feature choice remains visible across versions, but a mode that the operating system cannot provide is mapped to the closest supported backend. The classic View UI, legacy media-button receiver, pre-channel notifications, pre-23 audio recording/playback, pre-21 codec buffers, multidex and desugared Java APIs keep the same application flow available on API 19.

Emulator checks do not validate T3 USB drivers, Bluetooth RFCOMM, radio behavior, iPhone accessory acceptance, HUD integration or sustained video/audio. The current API 19 software checks and their exact limits are recorded in [T3 / Android 4.4 validation](T3-ANDROID44-VALIDATION.md); do not infer a physical connection result from an installation or UI test.

## BYD HUD and car hotspot

See [BYD navigation](BYD_NAVIGATION.md) for the exact verified firmware and lifecycle limits. Earlier car-hotspot builds started CarPlay on the development car using scoped IPv6. Current access-point endpoints prefer usable IPv4 and retain scoped IPv6 fallback. The phone must join the configured car hotspot. Neither result guarantees support on every firmware.

## Android 9 Wi-Fi Direct and experimental features

The Android 9 path creates or reuses a persistent system profile with the public legacy group API, reads generated credentials and uses the firmware channel setter where available. It serializes pinning/cancellation, avoids foreign groups and removes only its owned active group; persistent profiles are not deleted. Unknown setter outcomes stop startup, and unreliable pinning/cleanup should use the manual car hotspot. See [legacy limits](ANDROID9_WIFI_DIRECT.md); the contributor's Redmi K20 Pro result does not validate every BYD Android 9 firmware.

DiLink 3 call controls/dashboard cards and AAC-LC buffered music are independent default-off experiments. They appear in **Settings → Navigation → BYD navigation** (or **Advanced → Advanced vehicle data** when that card is unavailable), and **Advanced → Video and audio** for buffered music. Their corrected source has regression coverage; full call/audio/microphone/restoration and music-interruption acceptance remains device work. DiLink 4 casting/picture fixes describe the tested 2022 Seal setup, not a Qin/Seal-wide guarantee. The Android 13+ hotspot join helper requires strict user-configuration/5 GHz/API/ADB gates and explicit confirmation. See [0.2.14 release notes](RELEASE-NOTES-0.2.14.md).

## Current settings and opt-in limits

**Settings → Display** holds resolution, frame rate, icon/text size, appearance and Interface size; Interface size changes DiPlay controls, not CarPlay geometry. **Audio** holds routing and the ordinary music-buffer choice. **Navigation** holds location/BYD guidance, **Vehicle** holds gestures/wheel keys/car-button controls, **Connection** holds transport/startup/permissions, **Advanced** holds experimental display/media and vehicle data, and **Diagnostics** exports reports.

**Smooth video (experimental)**, **Call echo cancellation (experimental)** and **Clearer call voices (experimental)** are off by default under **Settings → Advanced → Video and audio**. Smooth video adds adaptive pacing delay, can delay touch response, and uses a SurfaceView path without picture adjustments. Changing it reconnects a running session. The call-processing controls apply at the next connection; source/JNI tests do not establish acoustic quality on a car. Optional rotation, split-screen areas and side panel are off by default under **Advanced → Display (experimental)**. Existing opted-in settings are retained during an in-place update.

The specifically observed 1280×480 DiLink 3 projection surface is now recognized by the existing cluster-map path. Actual map output still needs an on-car retest; the measured 1920×720 calibration is not applied to that smaller panel. Narrow USB framing/queue repairs and Bluetooth receive fixes have regression coverage, but they do not establish a fix for every connection report. A charging-only USB port cannot supply the data transport.

## Known limitations

- If the iPhone leaves its current Wi-Fi network but does not join the car hotspot, check that Auto-Join is enabled for that hotspot. If selecting it manually starts CarPlay without a password prompt, record that distinction in the diagnostic report. AP broadcast information elements can affect automatic joining even when credentials and the subsequent CarPlay transport work. See [automatic hotspot joining](WIRELESS_HOTSPOT_JOIN.md) for Apple's documented requirements and a controlled comparison; this does not establish a supported fix for every head unit or iOS version.
- Some units stutter, particularly under higher video load. A 2.4 GHz link alone does not prove the cause: interference, firmware and decoder stalls can all contribute. Try Default icons, 30 fps and a lower resolution, then attach a report.
- For the Wi-Fi channel and the picture size that gave the smoothest result on a BYD Tang, and why, see [Smooth wireless CarPlay](SMOOTH_WIRELESS.md).
- A contributor reported periodic wireless CarPlay stutter on a 2023 Han with GCC DiLink 3 when the car's Wi-Fi client was disconnected: scans every 10 s took the radio off the CarPlay channel for 3-6 s. On Android 10, with network ADB already authorized and the framework transaction available, DiPlay pauses connectivity scans for hotspot/P2P sessions. Same LAN is excluded so station reconnect and roaming remain available. Controller leases share one serial worker; scans restore after the last lease closes. A durable marker precedes suppression, failed restores retry every 30 s while the app runs, and app startup recovers an interrupted restore. A force-stop can delay restoration until the app is opened again. Missing approval or transaction support leaves scans alone. The updated in-app lifecycle needs a parked vehicle retest; without ADB, joining the car to a hotspot also slowed scans in the contributor's test.
- Some iOS/head-unit combinations do not visibly apply icon and text size. Reconnection is implemented; that does not guarantee the iPhone chooses the requested layout.
- A radio that supports joining a 5 GHz network may still reject a 5 GHz Wi-Fi Direct group. The capability flag is diagnostic, not proof of group-owner support.
- Automatic startup depends on the car's firmware and startup permissions.
- USB requires a data port and correct host/device-role behavior.
- Calls, Siri, background reconnection, long journeys and future iOS releases need broader testing.
- Source-only debug builds intentionally omit the MFi identity. They run for development and diagnostics but cannot authenticate a CarPlay session until the external assets described in [the build guide](BUILD.md) are supplied.

For a current report, reproduce the problem on **0.2.14**, then open **Settings → Diagnostics → Save diagnostic report**. Android 10+ normally saves to **Downloads/DiPlay**; Android 9 uses a document picker. The confirmation identifies fallback storage and offers **View report** and **Share**. Attach the reviewed `.txt` to a matching [existing issue](https://github.com/shihabal3amri/DiPlay/issues), or [create an issue](https://github.com/shihabal3amri/DiPlay/issues/new/choose). Include car/head-unit, Android/DiLink/firmware, iPhone/iOS, connection mode, steps and failure time. Nothing uploads automatically.

Reports record requested frequencies, station association state, fallback failures and remembered-configuration events. Android 10+ can verify the actual group frequency; Android 9 reports its accepted channel request as unverified and system-default as channel 0. Wi-Fi credentials and protocol payloads are excluded. A successful hotspot is not itself a successful CarPlay session.

Android references: [SupplicantState](https://developer.android.com/reference/android/net/wifi/SupplicantState), [explicit P2P operating frequency](https://developer.android.com/reference/android/net/wifi/p2p/WifiP2pConfig.Builder#setGroupOperatingFrequency(int)).