File content as of revision 4:3ceebacef5f1:

/* Joystick
 
Example code of how to read a joystick
 
https://www.sparkfun.com/products/9032
 
Craig A. Evans
7 March 2015
*/
 
#include "mbed.h"
#include "N5110.h"
 
// change this to alter tolerance of joystick direction
#define DIRECTION_TOLERANCE 0.05

//         VCC,    SCE,   RST,   D/C,   MOSI,  SCLK,   LED
N5110 lcd (PTD3, PTA0 , PTC4 , PTD0 , PTD2 , PTD1 , PTC3);
// Can also power (VCC) directly from VOUT (3.3 V) -
// Can give better performance due to current limitation from GPIO pin 
 
// connections for joystick
DigitalIn button(PTB18);
AnalogIn xPot(PTC11);
AnalogIn yPot(PTC10);

// timer to regularly read the joystick
Ticker pollJoystick;
// Serial for debug
Serial serial(USBTX,USBRX);


 
// create enumerated type (0,1,2,3 etc. for direction)
// could be extended for diagonals etc.
enum DirectionName {
    UP,
    DOWN,
    LEFT,
    RIGHT,
    CENTRE,
    UNKNOWN
};

/// create enumerated type (0,1,2,3 etc. for current direction snake is travelling (not joystick reading))
enum CurrentDirection {
    up,
    down,
    left,
    right,
    centre,
};
CurrentDirection currentDirection = centre; /// intialise direction at beginning
 
// struct for Joystick
typedef struct JoyStick Joystick;
struct JoyStick {
    float x;    // current x value
    float x0;   // 'centred' x value
    float y;    // current y value
    float 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;

int printFlag = 0;
 
int pixels[84][48];

int randomX =  rand() % 83 + 1;     // randomX in the range 1 to 81
int randomY =  rand() % 47 + 1;     // randomY in the range 1 to 47
int randomXoddEven = randomX%2; // find out whether odd or even
int randomYoddEven = randomY%2;

int snakeTailX[100];
int snakeTailY[100];
int snakeTailLength;

int i = 41; // snake head origin x
int j = 23; // snake head origin y
int prev_i;
int prev_j;
int prev2_i;
int prev2_j;

// function prototypes
void calibrateJoystick();
void updateJoystick();
void joystickDirection();
void generateFood();
void newFruitValues();
void moveSnake();

 
int main()
{
    
    calibrateJoystick();  // get centred values of joystick
    pollJoystick.attach(&updateJoystick,1.0/10.0);  // read joystick 10 times per second

    
   

    
    srand(time(NULL));
      

    lcd.init();
    lcd.drawRect(i,j,1,1,1); // default snake position
    
    generateFood();
 
    while(1) {
        
        if (printFlag) {  // if flag set, clear flag and print joystick values to serial port
            printFlag = 0;
            
            joystickDirection();
            moveSnake();
        } 
            sleep(); // put the MCU to sleep until an interrupt wakes it up
    }
}
 

void calibrateJoystick() // read default positions of the joystick to calibrate later readings
{
    button.mode(PullDown);
    // 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;
    // read button state
    joystick.button = button;
 
    // 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;
    }
 
    // set flag for printing
    printFlag = 1;
}

void generateFood()
{
    while (randomXoddEven ==0 || randomYoddEven ==0 || lcd.getPixel(randomX,randomY) >= 1) { // do while x or y is even or pixel is on
        
        randomX =  rand() % 83 + 1;     // randomX in the range 1 to 81
        randomY =  rand() % 47 + 1;     // randomY in the range 1 to 47
   
    // serial.printf("X = %i\n",randomX); // debug
    // serial.printf("Y = %i\n\n",randomY);
        
        randomXoddEven = randomX%2; // find out whether odd or even
        randomYoddEven = randomY%2;  
        }
        
        lcd.drawRect(randomX,randomY,1,1,1);

}

void newFruitValues() // new fruit coordinate values are given before it is passed to the generateFood function
{
                 
        randomX =  rand() % 83 + 1;     // randomX in the range 1 to 81
        randomY =  rand() % 47 + 1;     // randomY in the range 1 to 47
        randomXoddEven = randomX%2; // find out whether odd or even
        randomYoddEven = randomY%2;
 
}

void joystickDirection() { // stcik direction for debug
 
 serial.printf("x = %f y = %f button = %d ",joystick.x,joystick.y,joystick.button);
 
            // check joystick direction
            if (joystick.direction == UP)
                serial.printf(" UP\n");
            if (joystick.direction == DOWN)
                serial.printf(" DOWN\n");
            if (joystick.direction == LEFT)
                serial.printf(" LEFT\n");
            if (joystick.direction == RIGHT)
                serial.printf(" RIGHT\n");
            if (joystick.direction == CENTRE)
                serial.printf(" CENTRE\n");
            if (joystick.direction == UNKNOWN)
                serial.printf(" Unsupported direction\n");

 }
 
void moveSnake() {
    
    if (joystick.direction == LEFT) { 
                if (currentDirection != right) { // change the currentDirection according to joystick input, providing
                currentDirection = left;         // it's not the opposite direction to the current direction
                }
                }
    else if (joystick.direction == RIGHT) {
                if (currentDirection != left) { // change the currentDirection according to joystick input, providing
                currentDirection = right;       // it's not the opposite direction to the current direction
                }
                }
    else if (joystick.direction == UP) {
                if (currentDirection != down) { // change the currentDirection according to joystick input, providing
                currentDirection = up;          // it's not the opposite direction to the current direction
                }
                }
    else if (joystick.direction == DOWN) {
                if (currentDirection != up) { // change the currentDirection according to joystick input, providing
                currentDirection = down;      // it's not the opposite direction to the current direction
                }
                }
                
                lcd.clear();
                prev2_i = prev_i; // previous coordinates of the previous snake head coordinates
                prev2_j = prev_j;
                prev_i = i; // previous coordinates of the snake head
                prev_j = j;
                
                if (currentDirection == left) { // shift snake head coordinates according to current direction
                i -= 2; }
                else if (currentDirection == right) {
                i += 2; }
                else if (currentDirection == up) {
                j -= 2; }
                else if (currentDirection == down) {
                j += 2; }
                
                lcd.drawRect(i,j,1,1,1); // snake head
                lcd.drawRect(prev_i,prev_j,1,1,1); // seg 1
                lcd.drawRect(prev2_i,prev2_j,1,1,1); // seg 2
                lcd.drawRect(randomX,randomY,1,1,1); // food
                
                if (i == randomX && j == randomY) { // if fruit is eaten
                    snakeTailLength++;
                    newFruitValues();
                    generateFood();  
                    }
                wait(1.0);
    
 }