File content as of revision 4:78a6a4330690:

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

  PinName const SDA = PTE25;
  PinName const SCL = PTE24;

#define MMA8451_I2C_ADDRESS (0x1d<<1)

#define intermediateState 0
#define flatState 1
#define rightState 2
#define leftState 3
#define downState 4
#define upState 5
#define overState 6

#define threshold 0.90

DigitalOut redLed(LED1);
DigitalOut greenLed(LED2);
DigitalOut blueLed(LED3);

int main(void)
{
    uint8_t systemState = flatState;
    int counter =0, error = 0, correction = 0;
    MMA8451Q acc(SDA, SCL, MMA8451_I2C_ADDRESS);
    //PwmOut rled(LED1);
    //PwmOut gled(LED2);
    //PwmOut bled(LED3);
    Serial pc(USBTX, USBRX); // tx, rx
    

    pc.printf("MMA8451 ID: %d\n", acc.getWhoAmI());

    while (true) {
        float x, y, z;
        x = acc.getAccX();
        y = acc.getAccY();
        z = acc.getAccZ();
        
        switch(systemState) {
            case flatState:
                if(abs(z)<threshold) {
                    systemState = intermediateState;
                }
                redLed.write(0);
                greenLed.write(1);
                blueLed.write(1); 
                break;
            case overState:
                if(abs(z)<threshold) {
                    systemState = intermediateState;
                }
                redLed.write(1);
                greenLed.write(0);
                blueLed.write(1);
                break;
            case rightState:
                if(abs(y)<threshold) {
                    systemState = intermediateState;
                }
                redLed.write(1);
                greenLed.write(1);
                blueLed.write(0);
                break;
            case leftState:
                if(abs(y)<threshold) {
                    systemState = intermediateState;
                }
                redLed.write(0);
                greenLed.write(0);
                blueLed.write(1);
                break;
            case downState:
                if(abs(x)<threshold) {
                    systemState = intermediateState;
                }
                redLed.write(1);
                greenLed.write(0);
                blueLed.write(0);
                break;
            case upState:
                if(abs(x)<threshold) {
                    systemState = intermediateState;
                }
                redLed.write(0);
                greenLed.write(1);
                blueLed.write(0);
                break;
            case intermediateState:
                if(abs(x)>threshold && x>0) {
                    systemState = upState;
                    pc.printf("Up State\r\n");
                    }
                else if(abs(x)>threshold && x<0) {
                    systemState = downState;
                    pc.printf("Down State\r\n");
                    }
                else if(abs(y)>threshold && y>0) {
                    systemState = leftState;
                    pc.printf("Left State\r\n");
                    }
                else if(abs(y)>threshold && y<0) {
                    systemState = rightState;
                    pc.printf("Right State\r\n");
                    }
                else if(abs(z)>threshold && z>0) {
                    systemState = flatState;
                    pc.printf("Flat State\r\n");
                    }
                else if(abs(z)>threshold && z<0) {
                    systemState = overState;
                    pc.printf("Over State\r\n");
                    }
                redLed.write(1);
                greenLed.write(1);
                blueLed.write(1);
                break;
                
        }
        
        wait(0.1);
        counter++;
        
        //pc.printf("X: %1.2f, Y: %1.2f, Z: %1.2f\n", x, y, z);
    }
}