I'm just learning C, so this one is probably better (it's certainly trimmer than what I had yesterday....):
#include <Wire.h>
// DS1621 demo
// -- by Jon McPhalen (www.jonmcphalen.com)
// -- 21 DEC 2007
// SDA pin is Analog4
// SCL pin is Analog5
// DS1621 has A2, A1, and A0 pins connected to GND
// device ID and address
#define DEV_TYPE 0x90 >> 1 // shift required by wire.h
#define DEV_ADDR 0x00 // DS1621 address is 0
#define SLAVE_ID DEV_TYPE | DEV_ADDR
// DS1621 Registers & Commands
#define RD_TEMP 0xAA // read temperature register
#define ACCESS_TH 0xA1 // access high temperature register
#define ACCESS_TL 0xA2 // access low temperature register
#define ACCESS_CFG 0xAC // access configuration register
#define RD_CNTR 0xA8 // read counter register
#define RD_SLOPE 0xA9 // read slope register
#define START_CNV 0xEE // start temperature conversion
#define STOP_CNV 0X22 // stop temperature conversion
// DS1621 configuration bits
#define DONE B10000000 // conversion is done
#define THF B01000000 // high temp flag
#define TLF B00100000 // low temp flag
#define NVB B00010000 // non-volatile memory is busy
#define POL B00000010 // output polarity (1 = high, 0 = low)
#define ONE_SHOT B00000001 // 1 = one conversion; 0 = continuous conversion
void setup()
{
Wire.begin(); // connect I2C
startConversion(false); // stop if presently set to continuous
setConfig(POL | ONE_SHOT); // Tout = active high; 1-shot mode
setThresh(ACCESS_TH, 27); // high temp threshold = 80F
setThresh(ACCESS_TL, 24); // low temp threshold = 75F
Serial.begin(9600);
delay(5);
Serial.println("DS1621 Demo");
int tHthresh = getTemp(ACCESS_TH);
Serial.print("High threshold = ");
Serial.println(tHthresh);
int tLthresh = getTemp(ACCESS_TL);
Serial.print("Low threshold = ");
Serial.println(tLthresh);
}
void loop()
{
int tC, tFrac;
tC = getHrTemp(); // read high-resolution temperature
if (tC < 0) {
tC = -tC; // fix for integer division
Serial.print("-"); // indicate negative
}
tFrac = tC % 100; // extract fractional part
tC /= 100; // extract whole part
Serial.print(tC);
Serial.print(".");
if (tFrac < 10)
Serial.print("0");
Serial.println(tFrac);
delay(500);
}
// Set configuration register
void setConfig(byte cfg)
{
Wire.beginTransmission(SLAVE_ID);
Wire.send(ACCESS_CFG);
Wire.send(cfg);
Wire.endTransmission();
delay(15); // allow EE write time to finish
}
// Read a DS1621 register
byte getReg(byte reg)
{
Wire.beginTransmission(SLAVE_ID);
Wire.send(reg); // set register to read
Wire.endTransmission();
Wire.requestFrom(SLAVE_ID, 1);
byte regVal = Wire.receive();
return regVal;
}
// Sets temperature threshold
// -- whole degrees C only
// -- works only with ACCESS_TL and ACCESS_TH
void setThresh(byte reg, int tC)
{
if (reg == ACCESS_TL || reg == ACCESS_TH) {
Wire.beginTransmission(SLAVE_ID);
Wire.send(reg); // select temperature reg
Wire.send(byte(tC)); // set threshold
Wire.send(0); // clear fractional bit
Wire.endTransmission();
delay(15);
}
}
// Start/Stop DS1621 temperature conversion
void startConversion(boolean start)
{
Wire.beginTransmission(SLAVE_ID);
if (start == true)
Wire.send(START_CNV);
else
Wire.send(STOP_CNV);
Wire.endTransmission();
}
// Reads temperature or threshold
// -- whole degrees C only
// -- works only with RD_TEMP, ACCESS_TL, and ACCESS_TH
int getTemp(byte reg)
{
int tC;
if (reg == RD_TEMP || reg == ACCESS_TL || reg == ACCESS_TH) {
byte tVal = getReg(reg);
if (tVal >= B10000000) { // negative?
tC = 0xFF00 | tVal; // extend sign bits
}
else {
tC = tVal;
}
return tC; // return threshold
}
return 0; // bad reg, return 0
}
// Read high resolution temperature
// -- returns temperature in 1/100ths degrees
// -- DS1620 must be in 1-shot mode
int getHrTemp()
{
startConversion(true); // initiate conversion
byte cfg = 0;
while (cfg < DONE) { // let it finish
cfg = getReg(ACCESS_CFG);
}
int tHR = getTemp(RD_TEMP); // get whole degrees reading
byte cRem = getReg(RD_CNTR); // get counts remaining
byte slope = getReg(RD_SLOPE); // get counts per degree
if (tHR >= 0)
tHR = (tHR * 100 - 25) + ((slope - cRem) * 100 / slope);
else {
tHR = -tHR;
tHR = (25 - tHR * 100) + ((slope - cRem) * 100 / slope);
}
return tHR;
}
