File content as of revision 0:2c98a4766d9f:

#include "mbed.h"
#include "string.h"
#include <string>

//Initialize PWM
PwmOut PWM1(p21);
Serial pc(USBTX, USBRX);

//Initialize variables that will be used to read
std::string input; 


int main()
{
    while(1){
        if(pc.readable()) {
            char c = pc.getc(); 
            x = strlen(input);
            //If enter is pressed process input
            if(c  == '\r'){
                //check to see if valid input
                if(sizeof(input) == 7){
                    pc.printf("%s",input);                        //print input for debugging
                    input.clear();                                //clear input
                    }
                //mark as invalid input clear data
                else{
                    input.clear();                                 //clear input
                    pc.printf("Invalid Input /n");                 //print space
                    }                
                }
            //Else add the character to current input
            else{
            // add character to current input string
            input = input + c;
            pc.printf("%s\n",input);                        //print input for debugging
            pc.printf("%d",sizeof(input));
            } 
            wait(0.1);
        }
        
        
        
    }
}