Ask HN: How does Apple CarPlay work?

[MichaelMug]

Questions I have that I could not find answers:

1. Is the iPhone rendering in in-car displays? What is the refresh rate?

2. Does the iPhone have direct access to the CAN bus?

3. What role do the infotainment units play? Do they play any role when CarPlay is in use? Processing data/running an Apple-provided OS? If it runs an Apple provided OS does it download this from the phone or is it preloaded? Can the phone push updates?

4. How does iOS control the instrument cluster?

[sturza]

1. no, probably same as the HMI capability 2. no 3. forwarding and giving access to necesaary capabilities 4. it does not

[Invertigrate → sturza]

It actually does render it although the car manufacturer chooses the template.

See page 18: https://developer.apple.com/carplay/documentation/CarPlay-Ap...

It does however both surprise and annoy me that a cable is required for running this in 2024 which is the reason to why I personally never use it.

[jetti → Invertigrate]

My car has wireless CarPlay and I use it daily. There is one quirk I have noticed and I’m not sure if it is a general issue with wireless CarPlay or just Volkswagen’s implementation and that is there are times that the phone gets disconnected and the infotainment screen goes black. My assumption is that it has to do with a signal that is stronger disrupting the connection causing the issue as it only happens in certain areas and not always. The latest area I know it will happen is on a bridge that is having construction done on it. When we get over the construction equipment the CarPlay disconnects and will reconnect a few minutes down the road. I’ve actually wanted to get a HackRF One to capture the signal and see if I could tell what it was but I can’t justify spending $300 for just that.

[sokoloff → jetti]

There's a complex intersection near my house where my aftermarket Atoto CarPlay head unit will also reliably disconnect. Fortunately, after a firmware update to the head unit, it will now at least reconnect automatically; previously, I'd have to disconnect and reconnect the phone.

(Without any data to support,) I believe it to be a complexity of map issue (maybe causing a buffer overflow) rather than an RF/WiFi interference issue. It seems far too repeatable for it to be an RF issue.

[jetti → sokoloff]

I would be curious if that intersection ever stop causing disconnects. There was an intersection that would cause disconnects only from one area of the intersection (the east side of the intersection) and one day the disconnects stopped. There was another area near a water tower that would also disconnect the CarPlay and that no longer causes an issue. There was a water pump station near the first intersection so I was thinking it could somehow be related to the operations of the equipment. I am betting that once the construction is done in the area I’m having issues currently the issues will go away.

[Invertigrate → jetti]

Could it simply be that you have auto-join enabled and that you're connecting to another network in that area?

[Jtsummers → Invertigrate]

Carplay can work wirelessly if the infotainment system is able to work that way. It's not a limitation on Apple's side with any recent-ish phone (this decade, at least, and I think late last decade). This is on the manufacturers.

[dave84 → Invertigrate]

You can get a wireless CarPlay adapter for cheap and just leave that plugged in.

And that page 18 seems to have nothing to do with the car manufacturer.

[fckgw → Invertigrate]

It doesn't need a cable. Even the base model Hyundais support Wireless CarPlay now.

[helij → Invertigrate]

As far as I know in some cars you don't need a cable.

[bilsbie]

I never understood how the wireless works. It seems like a weird mix of Wi-Fi and Bluetooth?