Raspberry Pi Car Computer

Update: You can find my latest update on the progress of my Raspberry Pi Car Audio System here.

I’m working on a Raspberry Pi as a music player in my car. I’m putting all my music on a SSD disk in lossless FLAC. I’ve already got hold of a 2×16 character LCD with six button from Adafruit that only uses two pins for communication with I2C. It’s easy to program and it has four different background colors.

Car Power Supply for Raspberry Pi

I need a power supply to install the Raspberry Pi in my car. It needs to convert 12V to 5 Volts for both the Raspberry Pi and the USB hub that’s needed for the SSD disk. There’s a description of a suitable low loss power supply in the magazine (free download) MagPi issue 6 on page 6. it uses the LM2576 buck switching regulator. It even have an on/off pin which I need so I can easily control it. There’s a problem that needs fixing. I don’t want the computer, SSD disk and USB audio car drawing power all the time, depleting the battery. So I’m going to use a AVR Attiny13 micro controller which is a very low power 8-pin chip that has external interrupt and a sleep mode. The micro controller will wake when the Ignition is turned on, and turn on the main power supply for the computer. When the ignition is turned off, the micro controller waits for thirty minutes, and then tells the Raspberry Pi to shut down gracefully, checks that it’s halted and then turn off the main power supply. After that, the micro controller goes into sleep mode. This will keep the power consumption at a minimal. The Attiny13 has its own low power buck converter, so it won’t drain the battery as much as the main power supply.

I’ve already got the power supply up and running. next step, see how it works when the engine is cranked, which makes the power from the battery to fluctuate. If it doesn’t work I need to check if the engine is cranking and not start the power supply until the cranking is done.

Next step, writing the software for the logic of the Attiny13. It’s been a while since I programmed an AVR micro controller, but it’s going to be fun.

Software

I’m going to use Logitech Sqeezebox server and I’m writing a front end connected for it and play the music out through an USB audio card using SqeezeSlave. I’m controlling it with a python program, and it is up and running but is still too rough around the edges. But I’ll put it on Github when it is ready. I’ll install a WIFI dongle and set up a ad hoc wifi network for editing playlists with my iPhone or iPad using iPeng HD. I usually just select a playlist when driving, but I have artist, album and song selection as well.

Why?

I want to be able to have all my albums in a lossless format in my car. It’s one of the few places where I can play music at the sound level I like (loud!). And making your own stuff is fun. And you get to decide how it operates.

I’ll keep you updated on my progress.