Revision 0:3262800b671c, committed 2022-02-04

Comitter:

ciarankane123

Date:

Fri Feb 04 23:40:21 2022 +0000

Commit message:

Project

Changed in this revision

diff -r 000000000000 -r 3262800b671c Joystick.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Joystick.cpp	Fri Feb 04 23:40:21 2022 +0000
@@ -0,0 +1,162 @@
+#include "Joystick.h"
+
+Joystick::Joystick(PinName vertPin,PinName horizPin,PinName clickPin)
+{
+    vert = new AnalogIn(vertPin);
+    horiz = new AnalogIn(horizPin);
+    click = new InterruptIn(clickPin);
+}
+
+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
+
+    // turn on pull-down for button -> this assumes the other side of the button
+    // is connected to +3V3 so we read 1 when pressed and 0 when not pressed
+    click->mode(PullDown);
+    // we therefore need to fire the interrupt on a rising edge
+    click->rise(callback(this,&Joystick::click_isr));
+    // need to use a callback since mbed-os5 - basically tells it to look in this class for the ISR
+    _click_flag = 0;
+
+}
+
+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 x value here is inverted to ensure the positive x is to the
+    // right. This is simply due to how the potentiometer on the joystick
+    // I was using was connected up. It could have been corrected in hardware
+    // by swapping the power supply pins. Instead it is done in software so may
+    // need to be changed depending on your wiring setup
+
+    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;
+}
+
+bool Joystick::button_pressed()
+{
+    // ISR must have been triggered
+    if (_click_flag) {
+        _click_flag = 0;  // clear flag
+        return true;
+    } else {
+        return false;
+    }
+}
+
+void Joystick::click_isr()
+{
+    _click_flag = 1;
+}

diff -r 000000000000 -r 3262800b671c Joystick.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Joystick.h	Fri Feb 04 23:40:21 2022 +0000
@@ -0,0 +1,109 @@
+#ifndef JOYSTICK_H
+#define JOYSTICK_H
+
+#include "mbed.h"
+
+// this value can be tuned to alter tolerance of joystick movement
+#define TOL 0.1f
+#define RAD2DEG 57.2957795131f
+
+enum Direction {
+    CENTRE,  // 0
+    N,       // 1
+    NE,      // 2
+    E,       // 3
+    SE,      // 4
+    S,       // 5
+    SW,      // 6
+    W,       // 7
+    NW      // 8
+};
+
+struct Vector2D {
+  float x;
+  float y;  
+};
+
+struct Polar {
+    float mag;
+    float angle;
+};
+
+/** Joystick Class
+@brief Acknowledgements to Dr Craig A. Evans, University of Leeds
+@brief  Library for interfacing with analogue joystick
+@upgraded Dr Edmond Nurellari, University of Lincoln
+
+Example:
+
+@code
+
+#include "mbed.h"
+#include "Joystick.h"
+
+//                  y     x     button
+Joystick joystick(PTB10,PTB11,PTC16);
+
+int main() {
+    
+    joystick.init();
+    
+    while(1) {
+    
+        Vector2D coord = joystick.get_coord();
+        printf("Coord = %f,%f\n",coord.x,coord.y);
+        
+        Vector2D mapped_coord = joystick.get_mapped_coord(); 
+        printf("Mapped coord = %f,%f\n",mapped_coord.x,mapped_coord.y); 
+        
+        float mag = joystick.get_mag();
+        float angle = joystick.get_angle();
+        printf("Mag = %f Angle = %f\n",mag,angle);
+        
+        Direction d = joystick.get_direction();
+        printf("Direction = %i\n",d);
+        
+        if (joystick.button_pressed() ) {
+            printf("Button Pressed\n");  
+        }
+          
+        wait(0.5);
+    }
+    
+    
+}
+
+* @endcode
+*/
+class Joystick
+{
+public:
+    
+    //              y-pot              x-pot            button
+    Joystick(PinName vertPin,PinName horizPin,PinName clickPin);
+    
+    void init();  // needs to be called at start with joystick centred
+    float get_mag();              // polar
+    float get_angle();            // polar
+    Vector2D get_coord();         // cartesian co-ordinates x,y
+    Vector2D get_mapped_coord();  // x,y mapped to circle
+    Direction get_direction();    // N,NE,E,SE etc.
+    Polar get_polar();            // mag and angle in struct form
+    bool button_pressed();        // read button flag set in ISR when button pressed
+    
+private:
+
+    AnalogIn *vert;
+    AnalogIn *horiz;
+    InterruptIn *click;
+    
+    int _click_flag;    // flag set in ISR
+    void click_isr();   // ISR on button press
+       
+    // centred x,y values    
+    float _x0;
+    float _y0;
+    
+};
+
+#endif
\ No newline at end of file