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Hello all. I'm not a C coder at all. This is a short C routine that
Calculates a CRC16. The Poly and Seed are correct for what I need.
Could someone help me out converting this to PB. Thanks
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Calculates a CRC16. The Poly and Seed are correct for what I need.
Could someone help me out converting this to PB. Thanks
Code:
word get_crc(ubyte *bufptr,word len)
{
register unsigned int
newCRC;
//Put the current byte in here.
ubyte
data;
int
bit_count;
//This seed makes the output of this shift based algorithm match
//the table based algorithm. The center 16 bits of the 32-bit
//"newCRC" are used for the CRC. The MSb of the lower byte is used
//to see what bit was shifted out of the center 16 bit CRC
//accumulator ("carry flag analog");
newCRC=0x00F32100;
while(len--)
{
//Get the next byte in the stream.
data=*bufptr++;
//Push this byte’s bits through a software
//implementation of a hardware shift & xor.
for(bit_count=0;bit_count<=7;bit_count++)
{
//Shift the CRC accumulator
newCRC>>=1;
//The new MSB of the CRC accumulator comes
//from the LSB of the current data byte.
if(data&0x01)
newCRC|=0x00800000;
//If the low bit of the current CRC accumulator was set
//before the shift, then we need to XOR the accumulator
//with the polynomial (center 16 bits of 0x00840800)
if(newCRC&0x00000080)
newCRC^=0x00840800;
//Shift the data byte to put the next bit of the stream
//into position 0.
data>>=1;
}
}
//All the data has been done. Do 16 more bits of 0 data.
for(bit_count=0;bit_count<=15;bit_count++)
{
//Shift the CRC accumulator
newCRC>>=1;
//If the low bit of the current CRC accumulator was set
//before the shift we need to XOR the accumulator with
//0x00840800.
if(newCRC&0x00000080)
newCRC^=0x00840800;
}
//Return the center 16 bits, making this CRC match the one’s
//complement that is sent in the packet.
return((~newCRC)>>8);
}
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