MazdaSpoof - A Tape Deck Emulator

In order to use the tape deck audio input a device is needed which can pretend to be the tape deck by correctly answering the base unit commands. Furthermore, it is also possible to react to the base unit commands to control an external device using the radio's controls.

MazdaSpoof attempts to do this. In it's most basic form it simply pretends to be a tape deck which allows use of the tape deck audio input. It also fakes responses for all the available buttons on the head unit. This allows us to do fancy things like basic iPod integration.

Software

The software is written in C for the ATtiny45, it can be ported to other AVRs without too much trouble. The code is licensed under GPL (version 3), so have fun with it!

Latest Code (version 1.0):

Archive of source code and schematics: mazdaspoof-1.0.tar.bz2
Binary image in Intel Hex format: spoof.hex
Browse the source: ./mazdaspoof/src/

Circuitry

Tape Deck Emulator

This diagram includes extra circuitry for iPod integration, if you don't need iPod integration you can do the following:

Connect pin 7 (PB2) of the ATtiny45 to ground (omit R2 and R3)
Leave pin 6 (PB1) of the ATtiny45 floating (omit R4 and R5)
Connect the input of regulator (78L05) to ACC (switched 12V) instead of B+ (constant 12V)
Use 10K input resistors for the left/right audio inputs

iPod Dock Connector Connections

Switched 5V Power Supply

To charge an iPod you'll need a suitable power supply, the 78L05 used in the Tape Deck Emulator can't supply enough current. Much simpler power supplies can be built (think relays) but I went with this because it'll fit nicely in the void under the head unit.

Notes:

Important: When dropping 7-9V at 500mA across a 7805 it's will get very hot. Use a big heat-sink (at least 2x2cm of metal) to prevent overheating.
The 2SA715 might be hard to find, but any large PNP transistor should work (like the TIP30C).