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

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

DigitalOut MUX(P1_25);      //Make the pin that controls which seven segment display is ON into an output pin.
                            //Create an instance for each segment piece to be a different output pin.
DigitalOut LEDA(P1_23);     //Seg A as output.
DigitalOut LEDB(P1_28);     //Seg B as output.
DigitalOut LEDC(P0_16);     //Seg C as output.
DigitalOut LEDD(P1_31);     //Seg D as output.
DigitalOut LEDE(P1_13);     //Seg E as output.
DigitalOut LEDF(P1_16);     //Seg F as output.
DigitalOut LEDG(P1_19);     //Seg G as output.
DigitalOut LEDDP(P0_23);    //Seg Decimal Point as output.

Ticker timeout;             //Create an instance of class Ticker called timeout.

                            //Declare global variables
int num = 0;                //Declare the counter number as 0.
int tens;                   //Declare variable to hold the tens digit.
int units;                  //Declare variable to hold the units digit.


//Array of variables which correspond to the bit output required by the seven seg to display a number.
//i.e. a call to this array with a digit 0-9 will return the 7 bit data that will show that number on the segments.
int segNums[10] = {63, 6, 91, 79, 102, 109, 125, 7, 127, 103};  

int main()
{
    timeout.attach(&attimeout, 1);  //Call attach function in timeout instance to call attimeout() every 1 second.
    LEDDP = 1;                      //Turn off the Decimal Points (Active Low).
    while(1) {                      //Continuous loop for the rest of the program.
        segout();                   //Call segout() function to output a character to the one of the seven segs. (It will alternate between segs on each call). 
    }
}

void attimeout()                    //Timer interrupt routine.
{
    if (num<99) {                   //If the counter number "num" is less than 99 then increment it.
        num++;                  
    } 
    else {
        num = 0;                    //Reset the counter number "num" when it is greater than or equal to 99.
    }

    int temp = num;                 //Put num into a temp variable so that it can be changed without affecting num.
    tens = 0;                       //Reset tens so that it can count from 0 again after the last round.

    while (temp >= 10) {            //When temp is greater than 10 there are tens to display.
        temp = temp - 10;           //Remove ten from temp
        tens++;                     //and add one on to tens.
    }                               //Check again whether temp is greater than ten. Repeat until all the tens have been but into the tens variable.
    units = temp;                   //When all the tens have been removed from temp, all that should be left are the units. Put these into the units variable.

}

void segout()                       //Function to output digits to seven segment displays.
{
    int bits;                       //Declare bits which is used to contain the bits that relate to the segment outputs.
    int out;                        //Declare out which is used to hold the current digit (tens or units) and then as the segNums index.
    
    LEDA = 1;                       //Turn off all segments before the output seven seg is changed. 
    LEDB = 1;                       //Otherwise the digits will be displayed on both seven segs causing blurring.
    LEDC = 1;                       //
    LEDD = 1;                       //
    LEDE = 1;                       //
    LEDF = 1;                       //
    LEDG = 1;                       //

    MUX = !MUX;                     //Once all segs are off, change seven seg digit.

    switch (MUX) {                  //Switch case used to place correct digit into output for the seven seg digit selected (by MUX).
        case 0:                     //If tens seven seg is selected by MUX.
            out = tens;             //Set output to tens.    
            break;                  //break to end switch-case.
        case 1:                     //If units seven seg is selected by MUX.
            out = units;            //Set output to units.
            break;                  //break to end switch-case.

        default:                    //If MUX does not equal 1 or 0 (error, should never happen). 
            out = 0;                //Show 0 on display.
            break;                  //break to end switch-case.
    }

    bits = ~segNums[out];           //Call the array segNums with the number that wants to be displayed. Set bits to equal the bitwise inverted (~) number.
                                    //The Bitwise Inverter (~) is used because the LEDs in the seven seg are active low.
                                    
                                    //The next section uses Bitwise AND (&) to filter out the value of each bit using "bits" and a bitmask.
    LEDA = bits & 1;                //Set LEDA to the value of the first bit of bits. 
    LEDB = bits & 2;                //Set LEDB to the value of the second bit of bits. 
    LEDC = bits & 4;                //Set LEDC to the value of the third bit of bits.
    LEDD = bits & 8;                //Set LEDD to the value of the fourth bit of bits.
    LEDE = bits & 16;               //Set LEDE to the value of the fifth bit of bits.
    LEDF = bits & 32;               //Set LEDF to the value of the sixth bit of bits.
    LEDG = bits & 64;               //Set LEDG to the value of the seventh bit of bits.

}