Maciej Rajtar / Mbed 2 deprecated OneWireDrv

Test 1-wire , working wtih parasite power and few sensors with mixed power supply.

Dependencies:   mbed

crc8.cpp

Committer:
macraj
Date:
2010-05-10
Revision:
0:1197076b78f4

File content as of revision 0:1197076b78f4:

#include <inttypes.h>

#define CRC8INIT	0x00
#define CRC8POLY	0x18              //0X18 = X^8+X^5+X^4+X^0

uint8_t	crc8 ( uint8_t *data_in, uint16_t number_of_bytes_to_read )
{
	uint8_t	 crc;
	uint16_t loop_count;
	uint8_t  bit_counter;
	uint8_t  data;
	uint8_t  feedback_bit;
	
	crc = CRC8INIT;

	for (loop_count = 0; loop_count != number_of_bytes_to_read; loop_count++)
	{
		data = data_in[loop_count];
		
		bit_counter = 8;
		do {
			feedback_bit = (crc ^ data) & 0x01;
	
			if ( feedback_bit == 0x01 ) {
				crc = crc ^ CRC8POLY;
			}
			crc = (crc >> 1) & 0x7F;
			if ( feedback_bit == 0x01 ) {
				crc = crc | 0x80;
			}
		
			data = data >> 1;
			bit_counter--;
		
		} while (bit_counter > 0);
	}
	
	return crc;
}