uint16_t DS1820_GetTemp()
{
uint16_t ret_val_u16 = 0;
DS1820_Reset();
DS1820_WriteByte(DS1820_SKIP_ROM);
DS1820_WriteByte(DS1820_CONVERT_T);
_delay_ms(2000);
DS1820_Reset();
DS1820_WriteByte(DS1820_SKIP_ROM);
DS1820_WriteByte(DS1820_READ_SCRATCHPAD);
ret_val_u16 = DS1820_ReadByte();
ret_val_u16 |= (DS1820_ReadByte()<<8);
return ret_val_u16;
}
void DS1820_AddrDevice( uint8_t pin, uint8_t nAddrMethod )
{
uint8_t i;
if ( DS1820_CMD_MATCHROM == nAddrMethod ) {
// address single devices on bus
DS1820_WriteByte( pin, DS1820_CMD_MATCHROM );
for (i = 0; i<DS1820_ADDR_LEN; i ++ ) {
DS1820_WriteByte( pin, romAddrOneWire[ i ] );
}
}
else {
// address all devices on bus
DS1820_WriteByte( pin, DS1820_CMD_SKIPROM );
}
}
uint8_t DS1820_FindNextDevice( uint8_t pin )
{
uint8_t idxByte;
uint8_t state;
uint8_t mask = 1;
uint8_t bitpos = 1;
uint8_t nDiscrepancyMarker = 0;
uint8_t bit_b;
uint8_t bStatus;
uint8_t next_b = FALSE;
// initialise ROM address
memset( romAddrOneWire, 0, 8 );
bStatus = DS1820_Reset( pin ); // reset the 1-wire
if ( bStatus || bDoneFlagOneWire ) { // no device found
nLastDiscrepancyOnewire = 0; // reset the search
return FALSE;
}
// send search ROM command
DS1820_WriteByte( pin, DS1820_CMD_SEARCHROM );
idxByte = 0;
do {
state = 0;
// read bit
if ( DS1820_ReadBit( pin ) != 0 ) {
state = 2;
}
__delay_us(120);
// read bit complement
if ( DS1820_ReadBit( pin ) != 0 ) {
state |= 1;
}
__delay_us( 120 );
// description for values of state:
// 00 There are devices connected to the bus which have conflicting
// bits in the current ROM code bit position.
// 01 All devices connected to the bus have a 0 in this bit position.
// 10 All devices connected to the bus have a 1 in this bit position.
// 11 There are no devices connected to the 1-wire bus.
// if there are no devices on the bus
if ( state == 3 ) {
break;
}
else {
// devices have the same logical value at this position
if ( state > 0 ) {
// get bit value
bit_b = (uint8_t)(state >> 1);
}
// devices have conflicting bits in the current ROM code
else {
// if there was a conflict on the last iteration
if ( bitpos < nLastDiscrepancyOnewire ) {
// take same bit as in last iteration
bit_b = ( ( romAddrOneWire[ idxByte ] & mask ) > 0 );
}
else {
bit_b = ( bitpos == nLastDiscrepancyOnewire );
}
if ( bit_b == 0 ) {
nDiscrepancyMarker = bitpos;
}
}
// store bit in ROM address
if ( bit_b != 0 ) {
romAddrOneWire[ idxByte ] |= mask;
}
else {
romAddrOneWire[ idxByte ] &= ~mask;
}
DS1820_WriteBit( pin, bit_b );
// increment bit position
bitpos++;
// calculate next mask value
mask = mask << 1;
// check if this byte has finished
if ( 0 == mask ) {
idxByte++; // advance to next byte of ROM mask
mask = 1; // update mask
}
}
