File content as of revision 2:afd0cb53867f:

#include "mbed.h"

/*comments: testing turning on and off of Pins for 7-segment diode
using https://developer.mbed.org/users/synvox/notebook/lpc1768-pinout-with-labelled-mbed-pins/ 
by Nenad Milosevic 
verification: put the black lead of a multimeter on pin 1 (gnd)
and put the red lead on pin 26, voltage varies between +3.28VDC and 0VDC */

/*test program to learn how to write code for a 4 digit, 7-segment LED display LDQ-N524R1
The schematic for this (COMMON CATHODE) display shows the following connections
schematic located at http://www.lumex.com/ldq-n514ri (open Specs PDF for drawing)
The Common Cathode means that to turn on the segments of the 7-segment (including decimal point)
you write a one to that segment.
For this 4 digit display (LDQ-N524R1), each digit works backward--like its wired Common Anode so
You write a ZERO to turn on the selected digit AND a ONE to turn off the digit.

Pin Out wiring guide:(connect the display pin # to XX mbed pin)

CONTROL   DISPLAY Pin#  MBED Pin#
----------------------------------
Digit1          12         14
Digit2          9          13
Digit3          8          12
Digit4          6          11
DP              3          10
A               11         21
B               7          22
C               4          23
D               2          24  
E               1          25 
F               5          26
G               5          27

There is no blanking on this display, 

Program demonstrates use of DigitalOut to control segments of 7-segment display for 4 digit display LDQ-N514R1  
Author: Cap'n Tim Johnson PE
Retired Professor
Wentworth Institude of Technology 
Dept. Electrical Engineering and Technology
Boston, MA
*/

DigitalOut myled1(LED1);  //used as signal light to indicate where "thou art".
DigitalOut myled2(LED2);
DigitalOut myled3(LED3);
DigitalOut myled4(LED4);

int main() {

int i = 1;  //wait time interval
  
//test of LED 7-segment diodes on 4 digit display
while(1){  
 myled1 = 1;          //turns on signal light for digit 1
 DigitalOut (p14, 0); //Turn on digit#1, Most Significant Digit
 DigitalOut (p21, 1); 
 DigitalOut (p22, 1); 
 DigitalOut (p23, 1); 
 DigitalOut (p24, 1); 
 DigitalOut (p25, 1); 
 DigitalOut (p26, 1); 
 DigitalOut (p27, 1); 
 DigitalOut (p10, 1); //decimal point
 wait (i);
 myled1=0;            //turns off signal light for digit 1 
 
 myled2=1;
 DigitalOut (p14, 1); //turn off digit1
 DigitalOut (p13, 0); //turn on digit2
 DigitalOut (p21, 1); 
 DigitalOut (p22, 1); 
 DigitalOut (p23, 1); 
 DigitalOut (p24, 1); 
 DigitalOut (p25, 1); 
 DigitalOut (p26, 1); 
 DigitalOut (p27, 1); 
 DigitalOut (p10, 1); //decimal point
 wait (i);
 myled2=0;            //turns off signal light for digit 2
 
 myled3=1;
 DigitalOut (p13, 1); //turn off digit2
 DigitalOut (p12, 0); //turn on digit3
 DigitalOut (p21, 1); 
 DigitalOut (p22, 1); 
 DigitalOut (p23, 1); 
 DigitalOut (p24, 1); 
 DigitalOut (p25, 1); 
 DigitalOut (p26, 1); 
 DigitalOut (p27, 1); 
 DigitalOut (p10, 1); //decimal point
 wait (i);
 myled3=0;            //turns off signal light for digit 3
 
 myled4=1;
 DigitalOut (p12, 1); //turn off digit3
 DigitalOut (p11, 0); //turn on digit4, Least Significant Digit
 DigitalOut (p21, 1); 
 DigitalOut (p22, 1); 
 DigitalOut (p23, 1); 
 DigitalOut (p24, 1); 
 DigitalOut (p25, 1); 
 DigitalOut (p26, 1); 
 DigitalOut (p27, 1); 
 DigitalOut (p10, 1); //decimal point
 wait (i);
 myled4=0;            //turns off signal light for digit 4
 DigitalOut (p11, 1); //Turn off digit4
 
 //they are all off
 wait (1);

 myled1=1;   //Signal all are about to turn on
 myled2=1; 
 myled3=1; 
 myled4=1;   //Signals all are about to turn on
 wait (1);

 DigitalOut (p14, 0); //Turn them all on
 DigitalOut (p13, 0);
 DigitalOut (p12, 0);
 DigitalOut (p11, 0);
 wait (i);
 
 DigitalOut (p14, 1); //Turn them all off
 DigitalOut (p13, 1);
 DigitalOut (p12, 1);
 DigitalOut (p11, 1);
 wait (1);
 
 DigitalOut (p14, 0); //Turn them all on as zeros
 DigitalOut (p13, 0);
 DigitalOut (p12, 0);
 DigitalOut (p11, 0);
 DigitalOut (p27, 0);
 wait (i);

 DigitalOut (p14, 1); //Turn them all off
 DigitalOut (p13, 1);
 DigitalOut (p12, 1);
 DigitalOut (p11, 1);
 wait (1);

DigitalOut (p14, 0); //Turn them all on as sevens
 DigitalOut (p13, 0);
 DigitalOut (p12, 0);
 DigitalOut (p11, 0);
 DigitalOut (p24, 0);
 DigitalOut (p25, 0);
 DigitalOut (p26, 0);
 DigitalOut (p27, 0);
 wait (i);

 DigitalOut (p14, 1); //Turn them all off
 DigitalOut (p13, 1);
 DigitalOut (p12, 1);
 DigitalOut (p11, 1);
 wait (1);
 
 myled1=0;      //end of program signal
 myled2=0;      //end of program signal
 myled3=0;      //end of program signal
 myled4=0;      //end of program signal
 }
}