Has anyone managed to connect Rpi to Head Unit?

[signalius]

I see that most people have problems connecting their iPhone to Rpi, and I'm curious if anyone has managed to connect Rpi to Head Unit via USB?
From what I've been able to determine and partially accomplish, the following steps should be taken (I'm working on Rpi5 with Rasbian 6.12.55):

1. Connect USB C to HeadUnit and Rpi

2. Configure USB C to be a device:
   sudo dtoverlay dwc2,dr_mode=peripheral

3. We configure USBC using functionfs and libcomposite

4. We should receive the appropriate USB frame and send a response:

            if (bmRequestType == 0xC0 && bRequest == 0x53) {
                uint8_t resp[4] = {0x01, 0x00, 0x00, 0x00};
                size_t len = wLength < sizeof(resp) ? wLength : sizeof(resp);
                ssize_t wd = write(ep0, resp, len);

5. USB roles are reversed, RPi becomes the host and HeadUnit becomes the device

6. We perform reconfiguration:

sudo dtoverlay -R
sudo dtoverlay dwc2,dr_mode=host

7. At the same time, we launch IP over USB:
   sudo modprobe cdc_ncm This is necessary for exchanging information and transmitting video and audio, but here it is only a configuration so that the HU receives an IP address (IPv6).
   We also need to have mDNS or Avahi configured so that the HU can get
   the list of available services

8. Using libusb, Rpi must communicate with HU using the Iap2 protocol. In this step, we need to send an authorization request and HU must authorize itself in relation to Rpi. We do not need an MFI chip for this because since we are authorizing HU, we simply send back that everything is OK with the certificate without checking anything.

9. Once we have communicated using IAP2, the HU will now try to connect to the http server with the _carplay-ctrl._tcp service on the port we announced in mdns or avahi. Here, the HU sends us a “GET /ctrl-int/1/connect” request, and we have to respond something like this:

HTTP/1.1 200 OK\r\n
Server: AirTunes/320.17.7\r\n 
Content-Type: application/x-apple-binary-plist\r\n
Connection: keep-alive\r\n

10. Now you need to send the video stream using the RTSP protocol
    ffmpeg -re -loop 1 -framerate 25 -i test.png -c:v libx264 -preset ultrafast -tune zerolatency -pix_fmt yuv420p -f rtsp rtsp://localhost:7000/mystream Unfortunately, this does not work because ffmpeg does not communicate with HU using the appropriate protocol.

My question is: has anyone managed to display at least an image, or preferably a video, on the Head unit screen?

[liuwentai]

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[tr1fled]

The truth is, it is not this simple. While yes, based on what it sounds like, your setup should be correct, but you are missing one key detail, encryption exchange and additional iAP2 channel setup via TCP.

Why are you trying to do this though?

[tr1fled]

Maybe you would be interested in contacting me via Discord? You can find me at @haumeium

I have dealt with making a CarPlay receiver so surely I can give you guideance on making a sender.

[signalius]

Maybe you would be interested in contacting me via Discord? You can find me at @haumeium

Sure, I'll get back to you on Discord ( @TomSignalius )

[signalius]

I make fork of this repo. Now is posible to compile on the Raspberry Pi 5 with Debian Trixie 13.3
https://github.com/signalius/WirelessCarPlay
However this software is still not working out of the box yet.
If you have connected MFI 3959 to Rpi you can test it:

$ sudo airplayutil mfi
MFi initialize.
I2C Device addr: 10
Interface: /dev/i2c-2
Init time: 986 ms
Certificate (0 ms):

+0000: 30820388 06092a86 4886f70d 010702a0 |0^^^^^*^H^^^^^^^| (908 bytes)
+0010: 82037930 82037502 01013100 300b0609 |^^y0^^u^^^1^0^^^|
+0020: 2a864886 f70d0107 01a08203 5d308203 |*^H^^^^^^^^^]0^^|
+0030: 59308202 41a00302 0102020f 2222aa15 |Y0^^A^^^^^^^""^^|
+0040: 0817aa06 aa9007aa 16780930 0d06092a |^^^^^^^^^x^0^^^*|
+0050: 864886f7 0d010105 05003081 83310b30 |^H^^^^^^^^0^^1^0|
+0060: 09060355 04061302 55533113 30110603 |^^^U^^^^US1^0^^^|
+0070: 55040a13 0a417070 6c652049 6e632e31 |U^^^^Apple Inc.1|
...

@45clouds any tips?