Joystick.h

00001 /**
00002 @file Joystick.h
00003 @brief Header file containing functions prototypes, defines and global variables for constructing joystick.
00004 @brief Example code of how to read a joystick with slightly changed for the game
00005 @https://www.sparkfun.com/products/9032
00006 @author Craig A. Evans
00007 @date 7 March 2015
00008 */
00009 
00010 #ifndef JOYSTICK_H
00011 #define JOYSTICK_H
00012 
00013 #define DIRECTION_TOLERANCE 0.25
00014 
00015 /**
00016 Joystick vertical direction
00017 @brief Analog input for joystick to send vertical directions data
00018 */
00019 AnalogIn yPot(PTB2);
00020 /**
00021 Joystick horizontal direction
00022 @brief Analog input for joystick to send horizontal direction data
00023 */
00024 AnalogIn xPot(PTB3);
00025 
00026 //! create enumerated type (0,1,2,3 etc. for direction)
00027 //! could be extended for diagonals etc.
00028 enum DirectionName {
00029     UP,
00030     DOWN,
00031     LEFT,
00032     RIGHT,
00033     CENTRE,
00034     UNKNOWN
00035 };
00036 //! struct for Joystick
00037 typedef struct JoyStick Joystick;
00038 struct JoyStick {
00039     double x;    // current x value
00040     double x0;   // 'centred' x value
00041     double y;    // current y value
00042     double y0;   // 'centred' y value
00043     int button; // button state (assume pull-down used, so 1 = pressed, 0 = unpressed)
00044     DirectionName direction;  // current direction
00045 };
00046 //! create struct variable
00047 Joystick joystick;
00048 /**
00049 Read default positions of the joystick to calibrate later readings
00050 */
00051 void calibrateJoystick();
00052 /**
00053 Update the current position of joystick
00054 */
00055 void updateJoystick();
00056 
00057 /////////////////////////////////////////////////
00058 /// Function Definitions
00059 /////////////////////////////////////////////////
00060 
00061 // read default positions of the joystick to calibrate later readings
00062 void calibrateJoystick()
00063 {
00064     // must not move during calibration
00065     joystick.x0 = xPot;  // initial positions in the range 0.0 to 1.0 (0.5 if centred exactly)
00066     joystick.y0 = yPot;
00067 }
00068 
00069 void updateJoystick()
00070 {
00071     // read current joystick values relative to calibrated values (in range -0.5 to 0.5, 0.0 is centred)
00072     joystick.x = xPot - joystick.x0;
00073     joystick.y = yPot - joystick.y0;
00074 
00075     // calculate direction depending on x,y values
00076     // tolerance allows a little lee-way in case joystick not exactly in the stated direction
00077     if ( fabs(joystick.y) < DIRECTION_TOLERANCE && fabs(joystick.x) < DIRECTION_TOLERANCE) {
00078         joystick.direction = CENTRE;
00079     } else if ( joystick.y < DIRECTION_TOLERANCE && fabs(joystick.x) < DIRECTION_TOLERANCE) {
00080         joystick.direction = UP;
00081     } else if ( joystick.y > DIRECTION_TOLERANCE && fabs(joystick.x) < DIRECTION_TOLERANCE) {
00082         joystick.direction = DOWN;
00083     } else if ( joystick.x < DIRECTION_TOLERANCE && fabs(joystick.y) < DIRECTION_TOLERANCE) {
00084         joystick.direction = RIGHT;
00085     } else if ( joystick.x > DIRECTION_TOLERANCE && fabs(joystick.y) < DIRECTION_TOLERANCE) {
00086         joystick.direction = LEFT;
00087     } else {
00088         joystick.direction = UNKNOWN;
00089     }
00090 }
00091 
00092 #endif