Welcome to our site, we are here solving the issue that many Volkswagen and not only Volkswagen car owners have, the problem of adding an auxiliary input to their factory fit car stereo so they can listen to MP3s in their cars. Many have already changed their factory fit car stereos for another CD or MP3 players, others are using an tape adapter or an FM Transmitter. We are offering the best solution here: direct sound connection will ensure the very best sound quality which it is not compromised by the use of an FM transmitter or cassette adapter. Or if you already have a CD Changer connected you may want to try this DIY solution.

If you  are the owner of a Volkswagen car that has in it a Volkswagen stereo which you  really like and you would like to listen CDs or MP3s in your car  you might want to read more on this page and you will see how easy is to do this, without buying a 400€ Phatbox Phatnoise MP3 device or a CD Changer. (Phatbox Phatnoise is no longer produced).

The factory fitted head units in the VAG cars (Volkswagen, Audi, Seat, Skoda), are not allowing an AUX input through the pins marked for the CD-Changer at the back of the Head Unit (Car Stereo), unless detects an CD Changer connected. The Head Unit will query the CD Changer and once it gets the right reply from it, it will open the audio AUX IN path. So looks like there is no way to connect to it your MP3 player or IPOD.

So, if you connect an audio source at the pins at the back and expect to hear anything when you press the CD button on your Head Unit, the only thing that will happen is that on the HU (Head Unit) display you will se the message NO CD CHANGER, so do not waste your money on buying an AUX IN cable that only has an mini ISO connector and an audio jack connector made for Blaupunkt  because will not work.

The only way to make it work is making the car stereo to believe that there is an CD Changer connected and this will make it open the AUX IN path.pen the AUX IN path.

At this very moment We are aware of two ways of solving this issue: the first one uses an AVR micro controller (ATMEL) and the second one involves a PIC controller. The second one seems to be more commune.

Here we offer the first solution the one that involves the AVR micro controller. Also we will provide links and information regarding the second solution which we will not support.        Atmel’s 8-bit Flash AVR Microcontrollers are the Industry’s First to Meet +150 Degrees Celsius in Automotive Qualification
Atmel announced the industry first 8-bit RISC Flash microcontroller to be qualified for operation up to +150 degrees Celsius (AECQ100 Grade 0).

Already available in -40 to +125 degrees Celsius operating temperature range, the ATmega88 AVR® microcontroller is now capable of withstanding automotive temperature extremes, thus allowing designers to distribute intelligence and control functions directly into gearboxes, engine sensors and actuators, transfer cases, turbochargers, and finally simplifying the wiring network.

Compared with the existing 8-bit ROM competition, Atmel's robust non-volatile memory technology offers an unmatched capability to designers. The EEPROM is ideal for storing data, and the self-programmable Flash allows for the code updating within an application even after system deployment. Using Atmel's Flash technology eliminates the expensive and time-consuming steps inherent in mask ROM-based microcontrollers.

     The scope is to trigger the car stereo into believing that there is an CD Changer connected to it. After a lot of research we have managed to put together a way of doing it.

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