File content as of revision 4:463abe5f5135:

/**
@file Joystick.h
@brief Header file containing functions prototypes, defines and global variables for constructing joystick.
@brief Example code of how to read a joystick with slightly changed for the game
@https://www.sparkfun.com/products/9032
@author Craig A. Evans
@date 7 March 2015
*/

#ifndef JOYSTICK_H
#define JOYSTICK_H

#define DIRECTION_TOLERANCE 0.25

/**
Joystick vertical direction
@brief Analog input for joystick to send vertical directions data
*/
AnalogIn yPot(PTB2);
/**
Joystick horizontal direction
@brief Analog input for joystick to send horizontal direction data
*/
AnalogIn xPot(PTB3);

//! create enumerated type (0,1,2,3 etc. for direction)
//! could be extended for diagonals etc.
enum DirectionName {
    UP,
    DOWN,
    LEFT,
    RIGHT,
    CENTRE,
    UNKNOWN
};
//! struct for Joystick
typedef struct JoyStick Joystick;
struct JoyStick {
    double x;    // current x value
    double x0;   // 'centred' x value
    double y;    // current y value
    double y0;   // 'centred' y value
    int button; // button state (assume pull-down used, so 1 = pressed, 0 = unpressed)
    DirectionName direction;  // current direction
};
//! create struct variable
Joystick joystick;
/**
Read default positions of the joystick to calibrate later readings
*/
void calibrateJoystick();
/**
Update the current position of joystick
*/
void updateJoystick();

/////////////////////////////////////////////////
/// Function Definitions
/////////////////////////////////////////////////

// read default positions of the joystick to calibrate later readings
void calibrateJoystick()
{
    // must not move during calibration
    joystick.x0 = xPot;  // initial positions in the range 0.0 to 1.0 (0.5 if centred exactly)
    joystick.y0 = yPot;
}

void updateJoystick()
{
    // read current joystick values relative to calibrated values (in range -0.5 to 0.5, 0.0 is centred)
    joystick.x = xPot - joystick.x0;
    joystick.y = yPot - joystick.y0;

    // calculate direction depending on x,y values
    // tolerance allows a little lee-way in case joystick not exactly in the stated direction
    if ( fabs(joystick.y) < DIRECTION_TOLERANCE && fabs(joystick.x) < DIRECTION_TOLERANCE) {
        joystick.direction = CENTRE;
    } else if ( joystick.y < DIRECTION_TOLERANCE && fabs(joystick.x) < DIRECTION_TOLERANCE) {
        joystick.direction = UP;
    } else if ( joystick.y > DIRECTION_TOLERANCE && fabs(joystick.x) < DIRECTION_TOLERANCE) {
        joystick.direction = DOWN;
    } else if ( joystick.x < DIRECTION_TOLERANCE && fabs(joystick.y) < DIRECTION_TOLERANCE) {
        joystick.direction = RIGHT;
    } else if ( joystick.x > DIRECTION_TOLERANCE && fabs(joystick.y) < DIRECTION_TOLERANCE) {
        joystick.direction = LEFT;
    } else {
        joystick.direction = UNKNOWN;
    }
}

#endif