18b20mac.txt

用于单片机使用18B20器件的MAC地址搜索

//-----------------------------------------------------------------------------
// Read and return the page data and SHA-1 message authentication code (MAC)
// from a DS2432.
//
int ReadPageMAC(int page, unsigned char *page_data, unsigned char *mac)
{
	int i;
	unsigned short data_crc16, mac_crc16;

	// set the speed to 'standard'
	SetSpeed(1);

	// select the device
	if (OWTouchReset()) // Reset the 1-Wire bus
		return 0; // Return if no devices found

	OWWriteByte(0xCC); // Send Skip ROM command to select single device

	// read the page
	OWWriteByte(0xA5); // Read Authentication command
	OWWriteByte((page << 5) & 0xFF); // TA1
	OWWriteByte(0); // TA2 (always zero for DS2432)

	// read the page data
	for (i = 0; i < 32; i++)
		page_data[i] = OWReadByte();
	OWWriteByte(0xFF);

	// read the CRC16 of command, address, and data
	data_crc16 = OWReadByte();
	data_crc16 |= (OWReadByte() << 8);

	// delay 2ms for the device MAC computation
	// read the MAC
	for (i = 0; i < 20; i++)
		mac[i] = OWReadByte();

	// read CRC16 of the MAC
	mac_crc16 = OWReadByte();
	mac_crc16 |= (OWReadByte() << 8);

	// check CRC16...
	return 1;
}