File content as of revision 4:f490860cf06d:

#include "mbed.h"
#include "MMA8451Q.h"
#include "SLCD.h"

/* 
Test of the accelerometer, digital I/O, on-board LCD screen.
 Looing at vector product of the x-y components of the accelerometer.
 Works pretty well. Still rough, program wise - sc 140710
 */

#define DATATIME 0.150
#define CHANGELIMIT .800
#define LEDON false
#define LEDOFF true
#define PROGNAME "ACCLCD341bom"
#define PRINTDBUG
// 
#if   defined (TARGET_KL25Z) || defined (TARGET_KL46Z)
  PinName const SDA = PTE25;  // Data pins for the accelerometer/magnetometer.
  PinName const SCL = PTE24;  // DO NOT CHANGE
#elif defined (TARGET_KL05Z)
  PinName const SDA = PTB4;
  PinName const SCL = PTB3;
#else
  #error TARGET NOT DEFINED
#endif

#define MMA8451_I2C_ADDRESS (0x1d<<1)
enum vectorStates {MIDDLESTATE, LANDSCAPESTATE, HORIZONTALSTATE}; 

SLCD slcd; //define LCD display

MMA8451Q acc(SDA, SCL, MMA8451_I2C_ADDRESS);
Serial pc(USBTX, USBRX);

float sqrt_newt(float argument) {
    float xsqr = argument;
    float xnew = 0.0;
    float epsilon = 10e-7;
    int intmax = 20;
    float fCube = 2.0;
    float xold = xsqr/fCube;
    float delta = 1;
    int cube = 2;
    float a = 0.333333;    
    int i = 0;
    
    while(delta > epsilon || i > intmax)
    {
        xnew = a*(pow(xsqr/xold, cube) + (fCube*xold));
        delta = abs(xnew-xold);
        xold = xnew;
        i++;
    }    
    return (xold);
}
   

void LCDMess(char *lMess, float dWait){
        slcd.Home();
        slcd.clear();
        slcd.printf(lMess);
        wait(dWait);
} 


int main() {
    float xAcc;
    float yAcc;
    float vector;
    DigitalOut greenColor(LED_GREEN);
    DigitalOut redColor(LED_RED);
    vectorStates PGMState = MIDDLESTATE;
    int ledState = LEDON;
    //Timer LEDTimer;
    char lcdData[10]; //buffer needs places for decimal pt and colon
    //LEDTimer.start();
    //LEDTimer.reset();
    
#ifdef PRINTDBUG
        pc.printf(PROGNAME);
#endif
// main loop forever 
    while(true) {

//Get accelerometer data - tilt angles minus offset for zero mark.
        xAcc = abs(acc.getAccX());
        yAcc = abs(acc.getAccY());     
 // Calulate vector sum of x and y reading.       
        vector = sqrt_newt(pow(xAcc,2) + pow(yAcc,2));
        
/*************************** STATE MACHINE ***********************/
        switch(PGMState)
        {
            case MIDDLESTATE:
                if(xAcc < CHANGELIMIT && yAcc < CHANGELIMIT)
                {
                    redColor.write(ledState);
                    greenColor.write(ledState);
                }
                else if(xAcc > CHANGELIMIT)
                {
                    PGMState = LANDSCAPESTATE;
                    
                }
                else if(yAcc > CHANGELIMIT)
                {
                    PGMState = HORIZONTALSTATE;
                }                
            break;
            case LANDSCAPESTATE:
                if(xAcc > CHANGELIMIT)
                {
                    redColor.write(ledState);
                    greenColor.write(!ledState);
                }
                else
                    PGMState = MIDDLESTATE;
            break;
            case HORIZONTALSTATE:
            if(yAcc > CHANGELIMIT)
            {
                
                redColor.write(!ledState);
                greenColor.write(ledState);
            }
            else
                PGMState = MIDDLESTATE;
            break;
        }
            
        
 
#ifdef PRINTDBUG
        pc.printf("xAcc = %f\r\n", xAcc);
        pc.printf("yAcc = %f\r\n", yAcc);
        pc.printf("vector = %f\r\n",  vector);
#endif

        sprintf (lcdData,"%4.3f",yAcc);
        LCDMess(lcdData, DATATIME);
// Wait then do the whole thing again.
        wait(DATATIME);
    }
}