AI Box Glossary: CarPlay, Android Auto, FOTA, EDL, QFIL and More

Threads about AI boxes are full of shorthand. This page explains each term in plain English and links to the pages where it matters. Terms are grouped by topic; use your browser’s find (Ctrl+F or Cmd+F) to jump to one.

The box and the car

AI box

A small Android computer that plugs into your car’s USB port. The car’s screen treats it like a phone running CarPlay or Android Auto, but the apps (video, maps, music) run on the box itself, with its own Wi-Fi, Bluetooth, microSD slot and usually a SIM slot. Carlinkit TBox, Ottocast Picasou, ApplePie UX999, Ownice and Wizcar boxes all work this way. See start here for the families.

Head unit (HU)

The car’s own infotainment system and screen. The box never replaces it; it only talks to it over CarPlay or Android Auto. Head-unit quirks (BMW iDrive, VW MIB, Chinese-brand systems) explain many connection problems.

CarPlay (CP) and Android Auto (AA)

The two protocols a head unit uses to show a phone’s interface. An AI box pretends to be an iPhone (CP) or an Android phone (AA). Wired CP or AA means the car needs a cable; wireless means it can connect over Wi-Fi and Bluetooth.

Protocol switching

Choosing whether the box presents itself to the car as CarPlay or Android Auto. On Carlinkit you switch with a physical button (on some models inside a pin-hole) or in software at Factory settings → 4545 → Other. If the box is set to a protocol your car does not support, the car will not see it at all. Owners with both protocols available often choose by which one gives better sound, calls or screen size. See switch between CarPlay and Android Auto.

Android Auto only (MGears Mstick4)

Some boxes speak only one protocol. The MGears Mstick4 works only with Android Auto: a car that supports CarPlay but not Android Auto cannot use it.

Wireless CarPlay to the car

Box-to-car wireless, as opposed to phone-to-box wireless. A few models (Carlinkit TBox Ultra 3 and Ultra 4) can connect to a head unit that has factory wireless CarPlay, which matters for BMWs. Most boxes still need the USB cable to the car.

Y-cable

A USB cable with two plugs on the car end: one carries data and power, the second adds power from another USB port or a charger. It is the most common fix for boxes that reboot under load. See AI box keeps rebooting.

CAN bus sleep

Cars shut down their internal network (the CAN bus) some time after you lock them. Some head units then take longer to wake up than the box, so the box starts before the car is listening. A start-up delay (4545 → Other → Delay start connection) is the usual fix. See car doesn’t detect the AI box.

OEM GPS

The car’s own GPS receiver. Carlinkit boxes can use it instead of their own (4545 → Other → Use OEM GPS). Not every car sends position data, and in Android Auto mode the car’s GPS is usually not used.

Hardware and chips

SoC (system on chip)

The main processor, graphics and modem on one chip. The SoC decides which firmware fits your box. Names you will see:

SoC	Found in	Notes
SDM450	Carlinkit TBox V3 (CPC-200 / S450)	Android 9
QCM2290	Carlinkit TBox Mini	Android 11
QCM6125 / SM6125	Carlinkit TBox Plus, early TBox Ambient, Ottocast Picasou 3 and 3 Lite, ApplePie UX999 Plus 2.0	Android 11 to 13 depending on model; ApplePie moved Plus 2.0 to Android 16 in 2026
SDM660	Carlinkit TBox Ambient and UHD (one version)	The UHD on SDM660 has an extra USB port
SM6225 / QCM6225	Carlinkit TBox Ambient, TBox UHD, Ottocast Picasou 3 Pro and OttoAibox Nano, Wizcar M3	Android 13
SM6115	Carlinkit TBox S2	Newer, not covered in depth here
SM6350 / QCM6350	Carlinkit TBox Ultra 1–4	Android 15, UFS storage
QCM6490, QCM4490	ApplePie UX999 Rocket	Android 13 or 14

SM vs QCM

Qualcomm sells the same silicon under two names: SM for phones and QCM for embedded products. QCM6225 and SM6225 are, for owners’ purposes, the same chip.

EM (668) and EAU (138)

The two hardware variants of the Carlinkit TBox Plus. Carlinkit’s own guide says the back label reads EM on the 668 version and EAU, JP or NA on the 138 version, and that their firmware cannot be mixed. One owner warned that some resold units carried the wrong label, so also check the model string in Settings → About. See which TBox do I have.

UFS and eMMC

Two kinds of built-in storage. The recovery tool must be told which one your box uses: the TBox Ultra uses UFS, and owners found Picasou 3 units with either type, each needing its own recovery files.

Throttling

When the chip gets hot, Android lowers its speed to protect it, and the box becomes laggy. Owners of SM6225 boxes reported throttling starting somewhere around 80–90 °C (176–194 °F). A cooler or a better-ventilated spot helps; see how hot is too hot.

Firmware and recovery

Firmware, build date

The box’s operating system. Carlinkit identifies builds by date (for example the 26 Dec 2025 build), shown in Settings → About. Firmware is specific to the model, chip and, for the TBox Plus, the variant. See the firmware tracker.

FOTA and local update

FOTA means firmware over the air. On Carlinkit boxes it is also the name of the update app, FOTA Update, which can install an update downloaded over the internet or, through Local update, a file from a FAT32 microSD card. See update TBox firmware locally.

Stock launcher

The home screen the box ships with. Set it as default before any firmware update: updates with a third-party launcher as default have reset or bricked boxes. See set the stock launcher before an update.

Third-party firmware

Builds made by someone other than the box maker (Bruxe, DuDu and a CarCar edition are the ones owners discuss). They change the menus and sometimes fix or break things the official firmware does differently. See third-party firmware for Carlinkit.

“Device not activated” and the QR code

A screen some Carlinkit builds show after an update until the box has reached the internet. Connecting through the SIM card usually clears it. See device not activated / QR code.

EDL (Emergency Download mode)

A Qualcomm recovery mode built into the chip, below Android. A box in EDL shows up on a Windows PC as “Qualcomm HS-USB QDLoader 9008”. It is how a box that no longer boots gets reflashed.

QFIL

Qualcomm Flash Image Loader, the Windows tool (part of Qualcomm’s QPST package) that writes a full firmware image to a box in EDL mode. It is the last-resort recovery method and is labelled Brick risk on this site. See TBox Ultra QFIL recovery.

Firehose (programmer)

A small loader file, named like prog_firehose_ddr.elf, that QFIL sends to the chip first so it can then write the storage. It must match the SoC. A “Sahara protocol error” in QFIL usually means the wrong programmer or an incomplete image set.

Recovery files

The complete image set (programmer plus partition files and XML descriptions) needed for a QFIL flash. Get them only from the manufacturer’s support channel for your exact model.

A/B partitions (boot_a, boot_b)

Newer Android devices keep two copies of key partitions and boot from one slot while the other can be updated. Rooting guides patch the boot image of the active slot, which is why they mention boot_a and boot_b.

Android tinkering

ADB (Android Debug Bridge)

Google’s command-line tool for talking to an Android device from a computer or another device. Most deeper fixes use it. See the ADB cheat sheet.

Engineering menu, factory settings, engineering codes

The hidden settings screen on many AI boxes, opened by typing a code such as 4545 into Settings → Other → Factory settings. Not to be confused with a factory reset. See engineering codes.

ADB mode (142618)

A Carlinkit-specific USB mode: the box stops acting as a CarPlay or Android Auto device and appears to a computer as an ADB device. Turn it off again before reconnecting to the car.

Developer options and Wireless debugging

Android’s hidden settings for developers. Wireless debugging lets ADB connect over Wi-Fi with an IP address and port. On many boxes developer options are reached by a code instead of tapping the build number.

Captive portal

A network that needs you to log in before it gives internet access, like hotel Wi-Fi. Android checks for one by contacting Google’s servers; when that check fails, it shows an exclamation mark on the Wi-Fi or mobile icon and some apps refuse to work. Turning the check off with ADB is the community fix; see exclamation mark on the Wi-Fi icon.

Verity (dm-verity)

Android’s check that the system partition has not been modified. Switching it off (adb disable-verity) lets you edit system files, but firmware updates then fail until you run adb enable-verity. See update fails after disabling verity.

build.prop

A text file of system settings. Editing it can enable hidden features such as multitouch, and a mistake in it can stop the box booting. Brick risk.

Root and Magisk

Root means full administrator access to Android. Magisk is the tool most owners use to get it, by patching the boot image and flashing it with QFIL. Brick risk, and it voids most warranties. See root a Carlinkit TBox with Magisk.

DHU (Desktop Head Unit)

Google’s Android Auto head-unit emulator for a computer. Owners use it to set up a box at home, without sitting in the car. See set up your box at home with DHU.

Multitouch

Using two fingers (pinch to zoom) on the car’s screen. Many head units pass only single touches to the box by default; enabling multitouch needs Magisk or a build.prop edit. See enable multitouch on TBox.

Screen, apps and sound

Launcher

The app that draws the home screen. Owners often replace the stock launcher with a third-party one such as CarCar Launcher. Before that works, the box’s own side navigation bar must be off. See third-party launcher stuck on “Loading phone”.

Navigation bar and floating button

Carlinkit’s left-hand dock (home, back, recent apps) and the round shortcut button that floats over apps. Both can be turned off: the dock in the engineering menu, the floating button with ADB. See remove the navigation bar and floating button.

Split screen

Two apps side by side, for example a map and a music player. On Carlinkit you build presets with code 121212; the stock launcher’s two-pane home screen is not the same thing. See split screen on Carlinkit.

DPI and Minimum width

How large Android draws everything. Changing Minimum width in developer options makes the interface fit a large or small car screen.

Hot-word

The always-listening wake phrase of a voice assistant (“Hey Google”, or the one built into many navigation apps). Turning hot-word detection off is the most-confirmed fix for crackling or muffled sound; see crackling or muffled sound.

44.1 kHz (Force Audio 44K)

An audio output setting in the 166888 engineering menu that forces a 44.1 kHz sample rate. It helps sound on some older boxes and makes it worse on some TBox Ultra units.

Data-only (modem) SIM

A SIM card or plan meant for routers and tablets rather than phones. Owners found that some phone-plan SIMs give no data in the box while a data-only plan works; carriers’ rules differ by country. See AI box SIM card not working.