#include "mbed.h"           //Include the mbed header file which contains the prototypes of the libraries used here (DigitalOut, Timer) as well as various syntax definitions.

void output(void);          //Function prototype - Must have either whole function or function
                            //prototype declared above main function to avoid errors.

DigitalOut R(P1_23);        //Create a DigitalOut instance for the Red light.
DigitalOut A(P1_19);        //Create a DigitalOut instance for the Amber light.
DigitalOut G(P1_31);        //Create a DigitalOut instance for the Green light.
DigitalOut MUX(P1_25);      //Create a DigitalOut instance for the multiplexing pin.

Timer timer;                //Create an ininstance of Timer to be able to use time functions.

//Set up integers for the a and b lights, set the time step to 1 and the swap variable which swaps the sequence to the opposite set of lights to 0.
int  aR, aA, aG, bR, bA, bG, timeStep = 1, swap = 0; 

int main()
{
    timer.start();      //Start the timer.
    
    while(1) {          //Start infinite loop for the rest of the program.
        
        //If the timer is between 0 and 4 timeSteps, hold red on one side and green on the other.
        //This same sequence will be used for both sides by swapping which way round the sequence is output.
        if (timer.read() >= timeStep * 0 && timer.read() < timeStep * 4) {
            //Set a lights.
            aR = 1;
            aA = 0;
            aG = 0;
            //Set b lights
            bR = 0;
            bA = 0;
            bG = 1;            
        }

        //If the timer is between 4 and 5 timeSteps, move green to amber and hold red on the other side.
        if (timer.read() >= timeStep * 4 && timer.read() < timeStep * 5) {
            //Set a lights.
            aR = 1;
            aA = 0;
            aG = 0;
            //Set b lights
            bR = 0;
            bA = 1;
            bG = 0;
        }

        //If the timer is between 5 and 6 timeSteps, move amber to red and hold red on the other side.
        if (timer.read() >= timeStep * 5 && timer.read() < timeStep * 6) {
            //Set a lights.
            aR = 1;
            aA = 0;
            aG = 0;
            //Set b lights
            bR = 1;
            bA = 0;
            bG = 0;
        }
        
        //If the timer is between 6 and 7 timeSteps, hold red and move to red and amber on the other side.
        if (timer.read() >= timeStep * 6 && timer.read() < timeStep * 7) {
            //Set a lights.
            aR = 1;
            aA = 1;
            aG = 0;
            //Set b lights
            bR = 1;
            bA = 0;
            bG = 0;         
        }
        
        //If the timer is between 7 and 8 timeSteps, restart the process with the sides swapped over as the process from this point is just a repeat of what has already happened.
        if (timer.read() >= timeStep * 7 && timer.read() < timeStep * 8) {
            
            swap = !swap;   //Invert the swap variable to swap over the light sets a and b.
            timer.reset();  //Reset the timer so that the sequence will start from the beginning.
                    
            
        }
        
        output();           //Call the output function every loop to keep the seven segment displays multiplexed.

    }
}

//output function multiplexes the seven segment displays and reverses the lights a and b when necessary.
void output (void)
{
    
    R = A = G = 1;                      //Set all LED's to off so that the image of one does not transfer to the other when the MUX pin is changed.
    
    MUX = !MUX;                         //Invert the MUX pin to swap which display is used.
    
    if (swap) {                         //If swap is 1 then put a to the left side and b to the right side.
        switch (MUX) {                  //Switch on the value of MUX
            case 0:                     //If MUX = 0 then output a to the left display.
                R = !aR;
                A = !aA;
                G = !aG;
                break;                 
            case 1:                     //If MUX = 1 then output b to the right display.
                R = !bR;
                A = !bA;
                G = !bG;             
                break;                 

            default:                    //If MUX does not equal 0 or 1 then put all LED's on.
                R = A = G = 0;               
                break;               
        }
    } 
    else {                              //If swap is not 1 then put a to the right side and b to the left side.
        switch (MUX) {                  //Switch on the value of MUX
            case 0:                     //If MUX = 0 then output b to the left display.
                R = !bR;
                A = !bA;
                G = !bG;                
                break;                 
            case 1:                     //If MUX = 1 then output a to the right display.
                R = !aR;
                A = !aA;
                G = !aG;                             
                break;                  

            default:                    //If MUX does not equal 0 or 1 then put all LED's on.
                R = A = G = 0;              
                break;                 
        }
    }
}