crc16

void setup() {
  // put your setup code here, to run once:
  byte ON[]={0xA5,0x05,0x4C,0x4C,0x42};
  KIRSP_cal_CRC16(ON, 5);
}

void loop() {
  // put your main code here, to run repeatedly:

}

/*The function KIRSP_cal_CRC16 takes two parameters:
Please do not modify
Revision 1.0b 6/26/09
unsigned char *CRC16_Data_Array     = A pointer to the data array containing binary data to be used for generating the CRC
unsigned short CRC16_Data_Array_Len = The number of bytes in the data array.

This optimized CRC-16 algorithm calculation uses no tables or EEPROM
Polynomial: x^16 + x^15 + x^2 + 1 (0xA001) <- The Key value 
Initial value: 0xFFFF
CRC-16 is normally used in disk-drive controllers. 
Modified for the Audrion/Freeduino 
The sending system will calculate a CRC and append it to the message. The receiving system will calculate a new
CRC based on the entire message - including the appended CRC bytes. The resulting CRC should be 0x0000. <-------------- 
If the CRC-16 calculated by the receiving system is not equal to zero, then an error occurred in the transmission and all
data should be ignored. */

// KIRSP Global Variables for CRC-16 Checking
unsigned char KIRSP_CRC16_Hi_Byte  = 0xFF;  // Do not modify
unsigned char KIRSP_CRC16_Low_Byte = 0xFF;  // Do not modify


unsigned int KIRSP_cal_CRC16(unsigned char *CRC16_Data_Array, unsigned short CRC16_Data_Array_Len) 
{ 
 unsigned int x = 0xFFFF; 
 unsigned int y;
 int i; 
 x ^= *CRC16_Data_Array;
 for (i = 0; i < 8; ++i)
 {
   if (x & 1)
     x = (x >> 1) ^ 0xA001; // <----The key
   else
     x = (x >> 1);
 }
 KIRSP_CRC16_Hi_Byte = highByte(x);
 KIRSP_CRC16_Low_Byte = lowByte(x);
 y = x;   
 CRC16_Data_Array_Len--; 
 *CRC16_Data_Array++;  
 while (CRC16_Data_Array_Len--)
 {
   y ^= *CRC16_Data_Array;
   for (i = 0; i < 8; ++i)
   {
     if (y & 1)
       y = (y >> 1) ^ 0xA001; // <---The Key
     else
       y = (y >> 1);
   }
   KIRSP_CRC16_Hi_Byte = highByte(y);
   KIRSP_CRC16_Low_Byte = lowByte(y);   
   *CRC16_Data_Array++;
 }  
 KIRSP_CRC16_Hi_Byte = lowByte(y);   // write to global variable
 KIRSP_CRC16_Low_Byte = highByte(y); // write to global variable
 return y;
} // end of KIRSP_cal_CRC16 function