some time ago the CD player of my car stereo receiver (Pioneer DEH-600BT bought in 2002) started to have problems reading disks and since it doesn't have an USB input, I tought about building my own car media center equipped with a touchscreen 7" LCD. After searching over the net among Adafruit, SainSmart, Tontech and others, the choice fell on Waveshare and their 7 Inch HDMI (B) LCD equipped with touchscreen. The screen resolution is 800x480, enough to display the RuneGUI and with the HDMI input there isn't the need to configure kernel, recompile drivers and so on, except for the touchscreen controller. Not being a "linux guru" (thus able to load RuneAudio and the GUI on a single Raspberry) the final system is composed by two Raspberries: one for the Rune "server" and one with the browser for the Rune GUI. I had just a PI2 and a B+ that were laying on my desk so I downloaded the Rune image and installed on the B+, then I used the PI2, being powerful than the B+, with Raspbian and the Epiphany browser. Since a DAC was needed, I chose the HiFiBerry DAC+ (phone jack version) that is connected directly to the AUX input of the stereo receiver. The last step was the power supply: I took two adjustable step-down (12V to 5V, 3A) connected directly to the car battery (via a fuse) and commanded by a small switch to turn everything off. The problem, now, was the shutdown of both raspberries. The one with the Rune "server" was simple since the shutdown command is launched directly from the browser, but the real problem was to shutdown the one with Raspbian where the browser was set to run fullscreen and covered the taskbar (and the "menu" button). So I added a physical pushbutton connected to the GPIO connector, monitored by a Python script that operates in the following way:
- if the button is pressed for less than 3 sec then only the browser is closed ("sudo pkill -f epiphany-browser") leaving Raspbian "up" - if the button is pressed for over 3 sec then the shutdown sequence is initiated ("sudo shutdown -h now"). In both cases the Rune "server" shutdown is launched from the GUI before pressing the pushbutton.
The Python script is loaded at boot and the button is monitored through "interrupts" so that the script doesn't load the CPU. The sound is very clean without hiss or noises even with the engine on, I expected some noise from the (cheap) step-down power supplies but probably their "noise" is beyond the audible frequencies.
Since my car is not equipped with a 2 DIN compartment I had to build a case. The case is built using plywood and then painted black...honestly the first version is too "deep" and the visual impact is a bit "aggressive", considering the dashboard. So I'm going to rework it a bit: now it's like a simple "cube box" so I will cut both sides so that they will have a "slanted" shape from one edge to the other refining the overall look. Then I will publish some pics Regards,
The red button it's used to close the browser (accessing the desktop of Raspbian) or, if pressed for over 3 sec., to shutdown the system. The other button is a "fake" button to cover a hole in the panel The new panel will have only one button and a USB socket (connected internally to the PI-Rune server) to connect the usb pen. Regards and Merry XMas