STEERING F-UNO: SERIAL STEERING WHEEL

This Project is a simple (easy & cheap) Steering Wheel Joystick using Arduino UNO (no support for USB protocol).

Introduction

The idea was to have a minimal (easy and cheap) Game Steering Wheel mainly to play (on Linux) Geoff Crammond's Grand Prix 4. The steering wheel and pedals are based on three potentiometers that are used to encode their postition and angle. For the comunication with the computer it uses (for now) an Arduino UNO, so only the a serial comunication is available: to simulate a joystick the library vgamepad is used.

The Game Steering Wheel consists of three main parts:

• steering wheel
• throttle and break pedals
• python driver

In what follow we are going to describe them in detail.

Components

Material

Steering Wheel and Pedals

For the steering wheel and the pedal, you need to print the models:

• FreeCAD has been used to design the The Steering Wheel 3D model.

• The FCStd file is in the directoy ./3Dprinter/freeCAD_models

In order to assemble it, one needs:

• 6 screw M3x20mm with a exagonal nut of 6mm
• 6 springs from clothespin: they are used for the gear (2) and the pedals ( 2 for each)

Electronic coomponents

The electronic component consists of only few parts

• Arduino UNO
• 2 potentiometer Alpha RV16AF-20-15K-B10K RV16AF20KB10KM for the pedals NOTE: If you use another type of potentiometer, you need to redesign the pedals
• 1 potentiometer Weltron 002045038792 WP20CS-08-60F1-10K-20%-LIN for the steering wheel
• At least 2 buttons C-TS695 TC-TS695 for the gear up, gear down. There are two optional buttons. NOTE: If you use another type of buttons, you need to redesign the holes for them
• wires

Cicuit

The cicuit is extremly simple:

It consists of just few parts:

• 4 buttons

  • 2 buttons are used to control the gears (UP/DOWN)
  • 2 buttons can be customize

• 3 potentiometers

  • 2 are for the pedals
  • 1 to decode the rotation of the steering wheel

• Arduino UNO: for the Arduino code see section Software: Arduino

• schema and simulation done with slimul IDE (simulator/joystick.sim1)

Software

The software consists of two main parts: Arduino and python driver.

Arduino

The arduino sketch is extremly simple: it just read the input from the different pins where potentiometers and buttons are connected and serialize them to the python driver via the serial port: it is just ;-separated line of the different values in a specific order. There are two type of messages:

• version 1 consist of only 5 values:

Position	Component	Type	pin
1	steering wheel	analog	PIN_WHEEL_INPUT
2	break pedal	analog	PIN_BREAK_INPUT
3	throttle pedal	analog	PIN_GAS_INPUT
4	right back button	digital	PIN_BTN_GEAR_UP
5	left back button	digital	PIN_BTN_GEAR_DOWN

• version 2 (#define VERSION 2) consist of 2 extra-values:

Position	Component	Type	pin
1	steering wheel	analog	PIN_WHEEL_INPUT
2	break pedal	analog	PIN_BREAK_INPUT
3	throttle pedal	analog	PIN_GAS_INPUT
4	right back button	digital	PIN_BTN_GEAR_UP
5	left back button	digital	PIN_BTN_GEAR_DOWN
6	left front button	digital	PIN_BTN_LEFT
7	right front button	digital	PIN_BTN_RIGHT

NOTE: that the Button are initilized in the pinMode INPUT_PULLUP, so a button press is read as a LOW signal, while the button not being pressed is read as HIGH.

Python Driver

The python driver has 3 component:

• the runner: it identifies the message version and create the corresponding VirtualJoystic<...>-object
• The VirtualJoysticks:
  • VirtualJoysticSimple: minimal joystick with two button (message version 1)
  • VirtualJoysticGP4: joystick with 4 button (message version 2) - the On linux only GAMEPAD_A and GAMEPAD_B seems to be working: in GP4 keys x, c are used to look left/right: This joystick simulates these key press with the 2 extra buttons with help of the library pyautogui.
• The ArduinoStateVn store the input from arduino and update the state of the joystick depending of the message version ArduinoStateV1, ArduinoStateV2

Calibration

In order to properly map the values of the potentiometer to proper ranges, the serial joystick needs to be calibrated.

At the end of the calibation the ranges can be saved into a file (default is os.path.expanduser('~/.joystic_configuration'))