#include "mbed.h"
//Input-output and serial I/O definitions
Serial pc(USBTX, USBRX); // tx, rx     
Serial xbee(PTD3, PTD2); // tx, rx             
DigitalOut  LedPin(LED1);
// Define API "IS" command-packet array here

int packetIS[] = {0x7E,0x00,0x0F,0x17,0x01,0x00,0x13,0xA2,0x00,0x40,0x8A,0xD9,0xB3,0x9D,0x34,0x02,'I','S'};    //0x17 = FRAME TYPE-remote command request,AT Command immediate.0x01 = FRAME ID,identifies the UART data frame for the host to correlate with a subsequent acknowledgement(If set to 0->no responce.0x49(I)/0x53(S) = AT Command=(2 ASCII characters=I,S).  
int  packetISlength = 18;         //array for setting up 8 bytes for the API ND command
const int dataISlength = 40;     //define the number of bytes in array dataND[] for XBee modules
//Define extra variables
unsigned int  bytecount_hi;
unsigned int  bytecount_lo;
unsigned int  bytecount;
unsigned int  counter;
unsigned int  chksum;
unsigned int  calculated_sum = 0; //calculated checksum
int dataIS[dataISlength];   //array which stores the data received from the xbee
int inputdata;
int SerialInput()  // This function reads UART after it has new data
{
    while (xbee.readable() == 0)         //wait for UART to have new data
    {
    }
    return (xbee.getc());               //get new data, return
}

//Main XBee program.This program asks a remote xbee module to reply with information about the state of it's digital and anlog pins
  
int main(void)
{
  LedPin = 1;               //turn test LED off to start
  //Transmit packetIS as requested using for and not while
  counter = 0;
 for (counter = 0; counter < packetISlength; counter++)
     {   
      xbee.putc(packetIS[counter]); // send the API packet
      if (counter > 2)   //we calculate the sum after the length bytes
      { 
      calculated_sum = calculated_sum + packetIS[counter];    // calculate the sum 
      }
     }   
  chksum = 0xFF- (calculated_sum & 0xFF); 
  xbee.putc(chksum) ; //calculate the proper checksum & send it to the xbee
  pc.printf("The checksum of the IS command is: %x",chksum);
  pc.printf("\n\r");         
  wait(1); 
  calculated_sum = 0;                                   
  chksum=0;   //clear the checksum value
              
  //The below program gets serial data sent by the XBee module and saves the data in an array of bytes for each module. 
   inputdata = SerialInput();
   if (xbee.readable())
     {
       if (inputdata == 0x7E)         //start byte of API frame
        {                                            
          bytecount_hi = SerialInput();
          bytecount_lo = SerialInput();
          bytecount = (bytecount_hi * 256) + bytecount_lo;     //number of bytes in message   
            for (counter = 0; counter < bytecount; counter++)    //put XBee data received in array
              {
              dataIS[counter] = SerialInput();
              if (counter > 2)   
                { 
                 calculated_sum = calculated_sum + dataIS[counter];
                }
              } 
          chksum = SerialInput();
         }                             //get checksum--last byte
          if (chksum != (0xFF - (calculated_sum & 0xFF)))        //do checksums match in case something went wrong
           {
           while(1)                                         //NO MATCH, flash LED forever
              {                                             //Error handling could go
              LedPin = 0;                                   //here instead.
              wait(1);
              LedPin = 1;
              wait(0.5);
              }
           }
        }                                                   //IF Checksums match, it proceeds for the next module
         
                                                            //OK, got data for all XBee modules
  LedPin = 0;                                               //turn on LED
  wait(0.5);                                                //half-second delay
  
  //print data in each XBee array as hex characters.Data shows up to the PC terminal
  pc.printf("\n\r");
      for (counter = 0; counter < dataISlength; counter++)
      {    
        pc.printf("%02X  ", dataIS[counter]);  //show up the information received from the remote xbee on our terminal
      }
      pc.printf("\n\r");       //start a new line in  the pc terminal window
 
  while(1)                                                  //end program in an infinite do-nothing
  {                                                         //loop????
  }
}