FastCarPlay/README.md

FastCarPlay

This is C++ implementation of carplay receiver for "Autobox" dongles. The purpose of the project is to make application lightweight to run on Raspberry PI Zero 2W using hardware decoding.

Dongles

The dongles are readily available from Amazon or Aliexpress labeled by Carlinkit. They also seems to have official web site https://www.carlinkit.com/. Devices might have different vendor and product id's. Check your with lsusb and update settings if necessary.

Setup

Dependencies

The project is based on SDL2, FFMPEG, LIBUSB. It use XXD for resource embedding.

sudo apt install build-essential xxd libsdl2-dev libsdl2-ttf-dev libavformat-dev libavcodec-dev libavutil-dev libswscale-dev libusb-1.0-0-dev libssl-dev

To run the application you also need to install runtime

sudo apt install ffmpeg libsdl2-2.0-0 libsdl2-ttf-2.0-0 libusb-1.0-0 libssl3

USB Permissions and device id

On linux app may not have permisiions to read USB device. You need to create udev rule to grant persmissions for dongle. First you need to figure out your idVendor and idProduct.

lsusb

You will see list of devices, try to find the one that looks like dongle. Also you might need to run lsusb several time, cause my dongle seems to be disconnecting all the time. You need to find line like

Bus 003 Device 066: ID 1314:1520 Magic Communication Tec. Auto Box

So in my case ID 1314:1520 shows idVendor 1314 and idProduct 1520. We need to use those to create udev rules. If yours are different you also need to put them in settings.txt and run application with settings.txt as argument. Remember that in settings.txt values are in decimal, so you need to convert hex values to base 10 first. Create udev rules, replace <Vendor> <Product> and <Your user> with your informations

echo 'SUBSYSTEM=="usb", ATTRS{idVendor}=="<Vendor>", ATTRS{idProduct}=="<Product>", GROUP="<Your user>", MODE="0660"' | sudo tee /etc/udev/rules.d/50-carlinkit.rules
## example
## SUBSYSTEM=="usb", ATTRS{idVendor}=="1314", ATTRS{idProduct}=="1520", GROUP="linux", MODE="0660"
sudo udevadm control --reload-rules
sudo udevadm trigger

Build and run

The application can be started with settings file. Sample of the settings file can be found in settings.txt. Make sure that you put proper device id in settings and app have access to usb (see previous step) The project is using make. You can edit ./conf/settings.txt after copy if needed. From the repository root run following

make clean
make release
mkdir ./conf
cp ./settings.txt /conf
./out/app ./conf/settings.txt

Customisation

You can change font and background images by replacing files in ./src/resource

• background.bmp for background image. Use BMP format only.
• font.ttf for font. Use TTF fdrmat only

The names of the file need to be exactly same. Resources are embedded in executable, remake the project to regenerate resources

make clean
make release

Keys

The following keys have been mapped:

• Left - navigate left
• Right - navigate right
• Enter - select active item
• Backspace - Go back
• f - toggle fullscreen mode

Status

What is working:

• Video
• Audio (multiple channels)
• Key navigation
• Simple touch

What is not working:

• Multi touch - i have no means to test it
• Microphone - that's next step for me to figure out how to feed sound
• Telephone - the listening part will work, but because there is no mic implementation you can't speak

Notes

Regardless the resolution there are 2 types of settings

• source-width source-height source-fps - defines what video parameters will be requested from device
• width height fps - defines video drawing resolution and fps

The SDL will anyway scale the image to your screen/window size using internal HW scaling, so ideally you should use same values for width and height. If the source parameters will be different the scaling will be applied, however that scaling is not hardware accelerated and can consume a lot of CPU. You can set the 'scaler' in setting to define scaling algorithm. On my Raspbery Pi Zero 2W even easiest algorithm loads CPU to 100% and cause fram drop.

Increasing FPS above Source-FPS will cause app to run UI loop with less delays and do more event polling. This can increase responsivenes of the system, but also will make X11 to use more resources.

Progress and plans

Done

• ✓ Implement direct buffer transfer from video decoder to renderer (should reduce amount of memory copies and CPU load)
• ✓ Control audio buffers better (now system use 3 decoding threads but in reality only 2 required)
• ✓ Reduce music volume when there is navigation messages
• ✓ Add abilities to run script on device connect and device disconnect
• ✓ Add encrypted USB communication option with magic code 0x55bb55bb for new firmware
• ✓ Improve touch responsiveness
• ✓ Protocol debugging option + python script to decode usb dumps
• ✓ Android Auto (have not tested much, but seems to work for me)

Next

• Add microphone support (Calls, Siri)
• CAR menu with status, settings and options to run custom scripts

Acknowledgement

The project is inspired and based on great work done by other developers:

• 
• 
• 
• 

The project is licenced under GPL-3 licence. See LICENCE for details. The project is using Open Sans font (https://fonts.google.com/specimen/Open+Sans). See FONT_LICENCE for details.

Finally

If you have any questions, suggestions or you find problems running this feel free to open issue.