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/