Wireless AA and CarPlay use a hotspot your car emits that your phone connects to and transfers the image/inputs/audio that way

Got into a weird situation recently where my cheap android head unit was displaying Car Play from my phone, but (Google Maps) audio from my partner's.

Directions weren't coming from my phone's speaker or the car, but testing audio in the Maps app did (from the car).

Still not sure what combination of connections it had managed to get itself into!

Wireless CarPlay uses Bluetooth to exchange SSID and key info before switching over to WiFi for the duration of the session.

Wow that's cursed, never realized that's how it worked.

Cursed is exactly how I would describe it - because it works great until it doesn’t and it of course gives you zero clue why it won’t connect.

Anecdotally, I just got back from a holiday trip across Europe and crossed four international borders. At every single border crossing, my CarPlay session disconnected, and I had to toggle CarPlay off and back on in my phone settings to reconnect. Very strange, and I still have no idea what caused it.

It's a good idea actually, but it's also really complex to get right.

Early version of Android Auto could transfer over USB 2.0 instead of Bluetooth, which works, but it's not near as high bandwidth.

> Early version of Android Auto could transfer over USB 2.0 instead of Bluetooth, which works, but it's not near as high bandwidth.

This sentence doesn't make much sense - Auto (and CarPlay) still work in wired mode over USB 2.0 if the head unit supports it. They never worked over Bluetooth.

(And they use less than 15Mbps so USB 2.0s 480MBps are more than enough)

They use Bluetooth to configure WiFi. Most people call that Bluetooth, but technically you are correct.

The way I understand it, the connection is negotiated via BT, but then wifi is used for the fat data pipe to run the display.

I thought the latest Bluetooth protocols were basically designed to hand off to an ad-hoc Wi-Fi connection between the two devices after the initial handshake. (Might be an oversimplification of the real protocol)

They didn't run over BT. BT is used to initiate communication and share the password to a wifi-network. It then uses that Wi-Fi network for most communication, keeping the BT channel strictly for telephony.

They actually run over WiFi (WiFi direct IIRC) - Bluetooth is mostly just used as a setup handshake and to help the head unit decide which phone in the car should be the one connected.

It uses Bluetooth to stream audio, but everything else happens through a WiFi connection exposed by the car that the phone automatically pairs with after the Bluetooth handshake.

Not sure about CarPlay, but Android Auto connects via wifi to the head unit for the video feed.

Not sure about carplay, but Android Auto wireless uses wifi for the video stream.

My car requires wired connectivity (USB) for Android Auto.

For a decent amount of the older android / CarPlay usb implementations - you can also buy little WiFi / USB dongles that perfectly enable wireless CarPlay - I’ve used them now on a few vehicles and they have been perfect !