This Maker hacked the stereo in his 2007 Volvo V70 and successfully added his own AUX input.
Karl Hagström wondered why his 2007 Volvo didn’t have an AUX (AKA line-in) input on its head unit. As he puts it, “2007 was before the big era of smartphones, but everyone owned a couple of dirt cheap MP3 players and iPod was a big thing.” I’ve personally often wondered why my 2006 automobile has “DVD audio” capability, but lacks this far more useful and much simpler input method.
Unlike me, however, Swedish engineer Hagström decided to do something about this deficit, using an Arduino Nano clone (ATmega328) and several other components. This allowed him to run an AUX connector into the eight-pin connectors on the back of the head unit. The hack itself reportedly cost him less than five dollars, unlike the 80-dollar off-the-shelf solution.
The trick to this setup (and the reason for the Arduino) is that the CD changer input that the AUX goes into can’t be selected unless it is actually connected to the changer, which gives the head unit an initialization routine. Once the Arduino simulates this, it’s just a matter of connecting the left and right audio channels plus ground into the correct socket and pins.
If you accomplish this hack yourself, you can pipe all of your favorite Limp Bizkit and No Doubt songs from your SanDisk MP3 player into your car — all without even using a cassette adapter! Check out the Maker’s entire project here.