MFA-Switcher

show the Oil temperature directly after start in your VW Golf 3:

The VR6 Engine is very picky with its oil temps, so every drivers first steps after starting the engine is hittin the MFA switch 5 times to see the oil temp in the so called "MFA-Display".

Why not make this automaticaly?

A ATtiny12 or ATtiny13 with a Transistor is all it takes to make this task for you 

it is small enough to go right into the gauge cluster of the Golf! See the Breadboard version on top of my "Debug" Unit:

The code is also simple! It waits 1sec after ignition is on, then switches the transitor 5 times and then goes to sleep.

Its written in Assembler as the AVRStudio cannot compile with the AVR-GCC for the ATtiny12...

/*
Projekt: MFA Umschalter

Automatisches Anwählen der Öltemperatur
im Golf 3 VR6 Tacho

Date: 21.09.2011
Autor: Stephan Martin
*/

.include "tn12def.inc"        //ATtiny12, Adjust to tn13def.inc if ATtiny13


sbi    DDRB, 4    ; output on Pin 5


ldi  R17, $0A
WGLOOP2:  ldi  R18, $C6
WGLOOP3:  ldi  R19, $C9
WGLOOP4:  dec  R19
brne WGLOOP4
dec  R18
brne WGLOOP3
dec  R17
brne WGLOOP2


//Pin 5x Toggeln

rcall toggle
rcall toggle
rcall toggle
rcall toggle
rcall toggle

//And Sleep!

ldi r16, 0b00110001        //Power Down and Sleep Enabled
out MCUCR, r16
sleep


//in case of broken sleep:

loop:    rjmp loop


//--------------------------------------------------------------------------------

//Toggle Subroutine
toggle:

sbi PORTB, 4
rcall delay
cbi PORTB, 4
rcall delay
ret

//delaying 0,1sec (at 1,2MHZ internal):
delay:
ldi  R17, $C7
WGLOOP0:  ldi  R18, $C8
WGLOOP1:  dec  R18
brne WGLOOP1
dec  R17
brne WGLOOP0
ret

This should work on a ATtiny12 or ATtiny13! A great tool for getting the timing right is here: http://www.home.unix-ag.org/tjabo/avr/AVRdelayloop.html

I did not even made a circuit board for it, just take a piece of breadboard and make it 

Credit:

DL1DOW got me on the Idea for this, his project had the same idea, but i thought i can make it smaller 

Hackaday got it postet: https://hackaday.com/2011/09/29/hacking-your-cars-multifunction-display/