Logitech G29, G920, G27 Handbrake

2021 update:

User Aasikkia new code for my handbrake. You can give a try. I'm currently using an analog handbrake made with a hall sensor, so i not using this design anymore.

I made an alternate code for this that works as a game controller instead of a keyboard and also instead of spamming the key a lot, it keeps the button activated continuously.
Oh and it also works with the latest Arduino IDE (1.8.16 as of today).

I used this library to make it: https://github.com/ArminJo/DigistumpArduino

To use this code you'll have to enter this link as additional board manager URL in Arduino IDE's preferences:
https://raw.githubusercontent.com/ArminJo/DigistumpArduino/master/package_digistump_index.json

When you have added the url, you'll have to install "Digistump AVR Boards" from board manager (select "Contributed" from the drop down menu to find it). After that you should be able to select "Digispark" from the board menu.

Now you should be able to copy and paste the code from here https://pastebin.com/sm8hMr0a and upload it to your handbreak :)

Code:
#include "DigiJoystick.h"

void setup() {
pinMode(0, INPUT);
digitalWrite(0, HIGH);
}

void loop() {
DigiJoystick.setButtons((char)(digitalRead(0) ? 0x00 : 0x01), 0x00);
DigiJoystick.update();
}

Thnx Aasikki for supporting this design, enjoy!

2018 update:
Items needed:

• 16 mm aluminum tube (you have to drill it an 8 mm hole)
• V3 Microswitch SPDT 16a Micro Switch (http://www.ebay.es/itm/V3-Microswitch-SPDT-16A-Micro-Switch/251827572523?hash=item3aa217cf2b:m:mONdUDFbmsgXjdcCSmAGbFg)
• Two bolts (3x30 mm) with 2 nuts.
• One bolt (8x50 mm) with 1 nut.
• One spring (i bought one from a chinese store, cut it and left 3 rings of it).
• One Digispark Usb ATTINY85 board (to emulate a key for our handbrake).
  I bought this one: http://digistump.com/products/1 (from aliexpress).
• Two wires.

Tools needed:
-Soldering Iron: You'll have to solder the P0 pin and GND to your Switch.
-Dremel alike tool.
-Driller (to make an 8 mm hole to our tube).
-Micro usb cable.

Software needed:
-Arduino IDE (https://www.arduino.cc/en/main/software). (I uised Arduino IDE 1.6.5)
You'll have to install the trinket keyboard library's and the Attiny85 board drivers (because Arduino IDE have to recognise the board).
-Digistump digispark drivers (https://digistump.com/wiki/digispark/tutorials/connecting).
-Handbrake board code (this code enables the board to push the COMMA keyboard button mapped to our switch).
Handbrake code download: https://drive.google.com/file/d/1ueVhz8GHW2HozKdMkt_V-fGilqvFoX9U/view?usp=sharing

The attiny85 hardcase is optional. You can change the way you map your handbrake switch. In 2015 i used and old Usb Joystick, but this time i used an Arduino board clone).

Once you have completed your DIY handbrake you'll have to screw it to your shifter.