Diff: main.cpp

Revision:

0:026fa541af7a

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Sun Mar 08 16:43:02 2015 +0000
@@ -0,0 +1,120 @@
+/* Joystick
+
+Example code of how to read a joystick
+
+https://www.sparkfun.com/products/9032
+
+Craig A. Evans
+7 March 2015
+*/
+
+#include "mbed.h"
+
+// change this to alter tolerance of joystick direction
+#define DIRECTION_TOLERANCE 0.05
+
+// connections for joystick
+DigitalIn button(p18);
+AnalogIn xPot(p19);
+AnalogIn yPot(p20);
+
+// 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
+};
+
+// 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;
+
+// function prototypes
+void calibrateJoystick();
+void updateJoystick();
+
+int main()
+{
+    calibrateJoystick();  // get centred values of joystick
+    pollJoystick.attach(&updateJoystick,1.0/10.0);  // read joystick 10 times per second
+
+    while(1) {
+
+        if (printFlag) {  // if flag set, clear flag and print joystick values to serial port
+            printFlag = 0;
+            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");
+
+        }
+
+    }
+}
+
+// read default positions of the joystick to calibrate later readings
+void calibrateJoystick()
+{
+    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;
+}
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