Customizing Crankshaft
All custom configuration files for Crankshaft must be stored in the /boot/crankshaft/custom/ folder.
From image 2018-03-09 (alpha 0.1.7) on, to use a wallpaper for the "plug the phone in" screen, simply put a PNG file named wallpaper.png (it might be case sensitive, the .png is lowercase, be careful) to the boot partition and inside the crankshaft folder. If you use Windows, boot is only partition your computer can see when you plug in your Cranskshaft SD card. Just drag the PNG file into the folder and enjoy your beautiful car screen :)
The wallpaper should have the dimensions 800px*480px (if you use the official screen), or whatever your screen resolution is.
You can add GPIO buttons to do really cool things - click here for diagram. You can use physical buttons to adjust the vol control and brightness control and activate the "OK Google" Assistant. Note that all the GPIO pins are customizable. You can change it to whatever you want. Volume control by GPIO is enabled by default, but everything else requires you to open the /boot/crankshaft/gpio2kbd.cfg and uncomment a single line.
Here is one example:
You can try looking at the /boot/crankshaft/gpio2kbd config file (just open the SD card with Windows). Say you want GPIO23 for NEXT track.
You have to look up what are mappable by looking at this list:
https://github.com/torvalds/linux/blob/master/include/uapi/linux/input-event-codes.h
You see:
https://github.com/torvalds/linux/blob/master/include/uapi/linux/input-event-codes.h#L243
#define KEY_NEXTSONG 163
Disregard the 163, it's irrelevant for us. Now, remove the KEY_ prefix. NEXTSONG is what we're interested in. Add a line that says:
NEXTSONG 23
GPIO23 should now map to the NEXTSONG button. All you have to do now is to boot up Crankshaft, go to OpenAuto settings, go to input and enable the shortcut key for NEXTSONG. Save, then you'll be golden.
Currently, OpenAuto has built-in support for those keys: