Due to a growing list of mechanical problems, it was time for my beloved Aurora to be recycled. To replace it I bought a 2000 Nissan Altima, and with a new car comes a new stereo installation. And a new installation means improvements, fixes and of course problems.
This time I added additional circuitry for input switching of four audio inputs, a universal volume control on the output, a usb port, bluetooth, and an auxiliary input. The new circuitry is based around an arduino leonardo and stuffed inside the same project box from the first build, which was a tight fit. Next time I’ll definitely use a bigger box.
I don’t have a schematic of the circuit because i never really planned it, just prototyped it on a breadboard then put it together on an arduino protoshield. I did however make a shitty block diagram in paint as best I could remember.
I started out with a Samsung galaxy tab plus tablet. I specifically wanted this tablet because it has a 30 pin connector with audio output, usb, and power in it, and the plan was that I could connect everything in one plug. Unfortunately I found out that a resistor in the connector determines how it functions and that it can only be a usb host OR an audio output and not both. Not sure why they made it like that, but obviously I used the connector for a usb host and the headphone jack as the audio output. The usb on the tablet is hooked to a usb hub which I added power to in order to charge it and power the external usb port. To convert the cars 12 volt power to 5 volts, I just took apart a 2 amp car charger and hard wired in the circuit board.
In the aurora I hooked into the steering wheel controls to control the tablet. The altima doesn’t have any, so I added some with clip on remote off ebay (like this one: http://www.buyincoins.com/item/3288.html#.VPFLPfmIgjE ). It communicates to the arduino via an ir sensor as well as another remote control. The arduino plugs into the usb hub and connects to the tablet and replicates a usb keyboard. The actions of the key presses were configured by creating a new key character map file.
As far as the audio end of things, basically I used a CD4052 multiplexer IC to connect 4 inputs and outputted it into a PGA2311 digital volume control IC. Adding bluetooth was as easy as hooking in a cheapo bluetooth audio receiver from ebay. I’m sure I broke a few audio design rules because there is some alternator whine, but I’ve kinda gotten used to it…..turning up the volume also gets rid of it.
All in all, it works pretty good. There’s a few hardware and software bugs that I’ve never gotten around to fixing, I’ve just gotten used to it. I would like to design an actual pcb to address some of the problems, but probably won’t ever get around to that.