Globalstar STX3 - CRC Calculation Routines

8545-0198-01 Revision 1.9 STX3 Users Manual
9/24/2020 Globalstar, Inc. Confidential and Proprietary Page | 22
5.3 Example CRC calculation routines for serial packets
The following example is written in the C programming language where:
int = 32 bits, short = 16 bits, char = 8 bits
unsigned short crc16_lsb(unsigned char *pData, int length)
{
unsigned char i;
unsigned short data, crc;
crc = 0xFFFF;
if (length == 0)
return 0;
do
{
data = (unsigned int)0x00FF & *pData++;
crc = crc ^ data;
for (i = 8; i > 0; i--)
{
if (crc & 0x0001)
crc = (crc >> 1) ^ 0x8408;
else
crc >>= 1;
}
} while (--length);
crc = ~crc;
return (crc);
}
USAGE: calculate the CRC for a message and update the message CRC
unsigned short crc = crc16_lsb(msg, msg [1]-2);
msg [msg [1]-2] = (unsigned char) (crc&0xFF);
msg [msg [1]-1] = (unsigned char) (crc>>8);