u8 DS18B20StartMeasure(u8 pin, u8 num, u8 resolution)
{
u8 res, busy = LOW;
u8 temp_lsb, temp_msb;
u16 temp;
switch (resolution)
{
case RES12BIT: res = 0b01100000; break; // 12-bit resolution
case RES11BIT: res = 0b01000000; break; // 11-bit resolution
case RES10BIT: res = 0b00100000; break; // 10-bit resolution
case RES9BIT: res = 0b00000000; break; // 9-bit resolution
default: res = 0b00000000; break; // 9-bit resolution
/// NB: The power-up default of these bits is R0 = 1 and R1 = 1 (12-bit resolution)
}
if (!DS18B20Configure(pin, num, 0, 0, res)) return FALSE; // no alarm
if (OneWireReset(pin)) return FALSE;
if (num == SKIPROM)
{
// Skip ROM, address all devices
OneWireWrite(pin, SKIPROM);
}
else
{
// Talk to a particular device
if (!DS18B20MatchRom(pin, num)) return FALSE;
}
OneWireWrite(pin, CONVERT_T); // Start temperature conversion
return TRUE;
}
u8 DS18B20Read(u8 pin, u8 num, u8 resolution, DS18B20_Temperature * t)
{
u8 res, busy = LOW;
u8 temp_lsb, temp_msb;
u16 temp;
switch (resolution)
{
case RES12BIT: res = 0b01100000; break; // 12-bit resolution
case RES11BIT: res = 0b01000000; break; // 11-bit resolution
case RES10BIT: res = 0b00100000; break; // 10-bit resolution
case RES9BIT: res = 0b00000000; break; // 9-bit resolution
default: res = 0b00000000; break; // 9-bit resolution
/// NB: The power-up default of these bits is R0 = 1 and R1 = 1 (12-bit resolution)
}
if (!DS18B20Configure(pin, num, 0, 0, res)) return FALSE; // no alarm
if (OneWireReset(pin)) return FALSE;
if (num == SKIPROM)
{
// Skip ROM, address all devices
OneWireWrite(pin, SKIPROM);
}
else
{
// Talk to a particular device
if (!DS18B20MatchRom(pin, num)) return FALSE;
}
OneWireWrite(pin, CONVERT_T); // Start temperature conversion
while (busy == LOW) // Wait while busy ( = bus is low)
busy = OneWireRead(pin);
if (OneWireReset(pin)) return FALSE;
if (num == SKIPROM)
{
// Skip ROM, address all devices
OneWireWrite(pin, SKIPROM);
}
else
{
// Talk to a particular device
if (!DS18B20MatchRom(pin, num)) return FALSE;
}
OneWireWrite(pin, READ_SCRATCHPAD);// Read scratchpad
temp_lsb = OneWireRead(pin); // byte 0 of scratchpad : temperature lsb
temp_msb = OneWireRead(pin); // byte 1 of scratchpad : temperature msb
if (OneWireReset(pin)) return FALSE;
// Calculation
// ---------------------------------------------------------------------
// Temperature Register Format
// BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0
// LS BYTE 2^3 2^2 2^1 2^0 2^-1 2^-2 2^-3 2^-4
// BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9 BIT8
// MS BYTE S S S S S 2^6 2^5 2^4
// S = SIGN
temp = temp_msb;
temp = (temp << 8) + temp_lsb; // combine msb & lsb into 16 bit variable
if (temp_msb & 0b11111000) // test if sign is set, i.e. negative
{
t->sign = 1;
temp = (temp ^ 0xFFFF) + 1; // 2's complement conversion
}
else
{
t->sign = 0;
}
t->integer = (temp >> 4) & 0x7F; // fractional part is removed, leaving only integer part
/*
t->fraction = 0; // fractional part
if (BitRead(temp, 0)) t->fraction += 625;
if (BitRead(temp, 1)) t->fraction += 1250;
if (BitRead(temp, 2)) t->fraction += 2500;
if (BitRead(temp, 3)) t->fraction += 5000;
*/
t->fraction = (temp & 0x0F) * 625;
t->fraction /= 100; // two digits after decimal
return TRUE;
}
u8 DS18B20Read(u8 pin, u8 num, u8 resolution, TEMPERATURE * t)
{
u8 res, busy = 0;
u8 temp_lsb, temp_msb;
switch (resolution)
{
case RES12BIT: res = Bin(01100000); break; // 12-bit resolution
case RES11BIT: res = Bin(01000000); break; // 11-bit resolution
case RES10BIT: res = Bin(00100000); break; // 10-bit resolution
case RES9BIT: res = Bin(00000000); break; // 9-bit resolution
default: res = Bin(00000000); break; // 9-bit resolution
/// NB: The power-up default of these bits is R0 = 1 and R1 = 1 (12-bit resolution)
}
DS18B20Configure(pin, num, 0, 0, res); // no alarm
if (OneWireReset(pin)) return FALSE;
if (num == SKIPROM)
{
// Skip ROM, address all devices
OneWireWrite(pin, SKIPROM);
}
else
{
// Talk to a particular device
DS18B20MatchRom(pin, num);
}
OneWireWrite(pin, CONVERT_T); // Start temperature conversion
while (busy == 0) // Wait while busy ( = bus is low)
busy = OneWireRead(pin);
if (OneWireReset(pin)) return FALSE;
if (num == SKIPROM)
{
// Skip ROM, address all devices
OneWireWrite(pin, SKIPROM);
}
else
{
// Talk to a particular device
DS18B20MatchRom(pin, num);
}
OneWireWrite(pin, READ_SCRATCHPAD);// Read scratchpad
temp_lsb = OneWireRead(pin); // byte 0 of scratchpad : temperature lsb
temp_msb = OneWireRead(pin); // byte 1 of scratchpad : temperature msb
OneWireReset(pin);
// Calculation
// ---------------------------------------------------------------------
// Temperature Register Format
// BIT7 BIT6 BIT5 BIT4 BIT3 BIT2 BIT1 BIT0
// LS BYTE 2^3 2^2 2^1 2^0 2^-1 2^-2 2^-3 2^-4
// BIT15 BIT14 BIT13 BIT12 BIT11 BIT10 BIT9 BIT8
// MS BYTE S S S S S 2^6 2^5 2^4
// S = SIGN
if (temp_msb >= Bin(11111000)) // test if temperature is negative
{
t->sign = 1;
temp_msb -= Bin(11111000);
}
else
{
t->sign = 0;
}
t->integer = temp_lsb >> 4; // fractional part is removed, it remains only integer part
t->integer |= (temp_msb << 4); // integer part from temp_msb is added
t->fraction = 0; // fractional part (
if (BitRead(temp_lsb, 0)) t->fraction += 625;
if (BitRead(temp_lsb, 1)) t->fraction += 1250;
if (BitRead(temp_lsb, 2)) t->fraction += 2500;
if (BitRead(temp_lsb, 3)) t->fraction += 5000;
t->fraction /= 100; // two digits after decimal
return TRUE;
}
