Diff: lib/Joystick.cpp

Revision:

0:be41a15e7a86

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/Joystick.cpp	Fri Dec 11 12:25:25 2020 +0000
@@ -0,0 +1,131 @@
+#include "Joystick.h"
+
+Joystick::Joystick(PinName vertPin,PinName horizPin)
+{
+    vert = new AnalogIn(vertPin);
+    horiz = new AnalogIn(horizPin);
+}
+
+void Joystick::init()
+{
+    // read centred values of joystick
+    _x0 = horiz->read();
+    _y0 = vert->read();
+
+    // this assumes that the joystick is centred when the init function is called
+    // if perfectly centred, the pots should read 0.5, but this may
+    // not be the case and x0 and y0 will be used to calibrate readings
+}
+
+Direction Joystick::get_direction()
+{
+    float angle = get_angle();  // 0 to 360, -1 for centred
+
+    Direction d;
+    // partition 360 into segments and check which segment the angle is in
+    if (angle < 0.0f) {
+        d = CENTRE;   // check for -1.0 angle
+    } else if (angle < 22.5f) {  // then keep going in 45 degree increments
+        d = N;
+    } else if (angle < 67.5f) {
+        d = NE;
+    } else if (angle < 112.5f) {
+        d = E;
+    } else if (angle < 157.5f) {
+        d = SE;
+    } else if (angle < 202.5f) {
+        d = S;
+    } else if (angle < 247.5f) {
+        d = SW;
+    } else if (angle < 292.5f) {
+        d = W;
+    } else if (angle < 337.5f) {
+        d = NW;
+    } else {
+        d = N;
+    }
+
+    return d;
+}
+
+// this method gets the magnitude of the joystick movement
+float Joystick::get_mag()
+{
+    Polar p = get_polar();
+    return p.mag;
+}
+
+// this method gets the angle of joystick movement (0 to 360, 0 North)
+float Joystick::get_angle()
+{
+    Polar p = get_polar();
+    return p.angle;
+}
+
+// get raw joystick coordinate in range -1 to 1
+// Direction (x,y)
+// North     (0,1)
+// East      (1,0)
+// South     (0,-1)
+// West      (-1,0)
+Vector2D Joystick::get_coord()
+{
+    // read() returns value in range 0.0 to 1.0 so is scaled and centre value
+    // substracted to get values in the range -1.0 to 1.0
+    float x = 2.0f*( horiz->read() - _x0 );
+    float y = 2.0f*( vert->read() - _y0 );
+
+    // Note: the values are negated so positive is up and right.
+    Vector2D coord = {-x,y};
+    return coord;
+}
+
+// This maps the raw x,y coord onto a circular grid.
+// See:  http://mathproofs.blogspot.co.uk/2005/07/mapping-square-to-circle.html
+Vector2D Joystick::get_mapped_coord()
+{
+    Vector2D coord = get_coord();
+
+    // do the transformation
+    float x = coord.x*sqrt(1.0f-pow(coord.y,2.0f)/2.0f);
+    float y = coord.y*sqrt(1.0f-pow(coord.x,2.0f)/2.0f);
+
+    Vector2D mapped_coord = {x,y};
+    return mapped_coord;
+}
+
+// this function converts the mapped coordinates into polar form
+Polar Joystick::get_polar()
+{
+    // get the mapped coordinate
+    Vector2D coord = get_mapped_coord();
+
+    // at this point, 0 degrees (i.e. x-axis) will be defined to the East.
+    // We want 0 degrees to correspond to North and increase clockwise to 359
+    // like a compass heading, so we need to swap the axis and invert y
+    float x = coord.y;
+    float y = coord.x;
+
+    float mag = sqrt(x*x+y*y);  // pythagoras
+    float angle = RAD2DEG*atan2(y,x);
+    // angle will be in range -180 to 180, so add 360 to negative angles to
+    // move to 0 to 360 range
+    if (angle < 0.0f) {
+        angle+=360.0f;
+    }
+
+    // the noise on the ADC causes the values of x and y to fluctuate slightly
+    // around the centred values. This causes the random angle values to get
+    // calculated when the joystick is centred and untouched. This is also when
+    // the magnitude is very small, so we can check for a small magnitude and then
+    // set the angle to -1. This will inform us when the angle is invalid and the
+    // joystick is centred
+
+    if (mag < TOL) {
+        mag = 0.0f;
+        angle = -1.0f;
+    }
+
+    Polar p = {mag,angle};
+    return p;
+}
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