This is the code I used, derived from the sheepdog method. Not such a great idea in principle but works fine if you have the pins to spare.
Another approach is to incorporate the address finder code. This enables you to still use the one-wire system.
/*
Reading two DS18B20s pins 14&15
display to monitor
display to LCD with pin D04 moved to pin 16 (A2)
Code uses Arduino LCD, sheepdog temp reader, SD stuff from Mellis & Igoe
*/
#define tture1 14//no ; here
#define tture2 15//no ; here
// include the library codes:
#include <LiquidCrystal.h>
#include <SD.h>
File myFile;
// initialize the library with the numbers of MY interface pins
LiquidCrystal lcd(8,9,16,5,6,7);
int HighByte, LowByte, TReading, SignBit, Tc_100, Whole, Fract;
void setup() {
//For each tture sensor: Do a pinMode and a digitalWrite
pinMode(tture1, INPUT);
pinMode(tture2, INPUT);
digitalWrite(tture1, LOW);//Disable internal pull-up.
digitalWrite(tture2, LOW);
Serial.begin(9600);
delay(300);//Wait for newly restarted system to stabilize
Serial.print("Temperature measurement, two sensors:\n\n");
// set up the LCD's number of columns and rows:
lcd.begin(16, 2);
lcd.clear();
// Print a message to the LCD.
lcd.print("temp in out");
Serial.print("Initializing SD card...");
pinMode(10, OUTPUT);
if (!SD.begin(4)) {
Serial.println("initialization failed!");
return;
}
Serial.println("initialization done.");
// open the file. note that only one file can be open at a time,
// so you have to close this one before opening another.
myFile = SD.open("test.txt", FILE_WRITE);//+++++++++++++++++++ OPEN
// if the file opened okay, write to it:
if (myFile) {
Serial.print("Writing to test.txt...");
myFile.println("testing! Did you forget the date?");
myFile.close();//++++++++++++++++++++++++++++++++++++++++++++ CLOSE
Serial.println("done.");
} else {
// if the file didn't open, print an error:
Serial.println("error opening test.txt");
}
}
void loop(){
// set the LCD cursor to column 4, line 1
// (note: line 1 is the second row, since counting begins with 0):
lcd.setCursor(4, 1);
readTture(tture1);//N.B.: Values passed back in globals
printTture();//N.B.: Takes values from globals. Also...
//no newline part of printTture;
delay(120);// Delay... must not be too short.
// set LCD cursor for second temp
lcd.setCursor(11, 1);
readTture(tture2);//Now read and report 2nd tture.
printTture();
delay(200);// Delay... must not be too short.
Serial.print("\n");//Start new line
myFile = SD.open("test.txt", FILE_WRITE);//+++++++++++++++++++++++++OPEN
myFile.println(", ");
myFile.close();//>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>CLOSE
delay(880);
}
//Everything below here... just copy it into your program "as is".
//You are only likely to need to use readTture(pin) and printTture()
// directly. Others are subordinate to those.
//These routine access the following global variables...
// int HighByte, LowByte, TReading, SignBit, Tc_100, Whole, Fract;
void OneWireReset(int Pin) // reset. Should improve to act as a presence pulse
{
digitalWrite(Pin, LOW);
pinMode(Pin, OUTPUT); // bring low for 500 us
delayMicroseconds(500);
pinMode(Pin, INPUT);
delayMicroseconds(500);
}
//end OneWireReset
void OneWireOutByte(int Pin, byte d) // output byte d (least sig bit first).
{
byte n;
for(n=8; n!=0; n--)
{
if ((d & 0x01) == 1) // test least sig bit
{
digitalWrite(Pin, LOW);
pinMode(Pin, OUTPUT);
delayMicroseconds(5);
pinMode(Pin, INPUT);
delayMicroseconds(60);
}
else
{
digitalWrite(Pin, LOW);
pinMode(Pin, OUTPUT);
delayMicroseconds(60);
pinMode(Pin, INPUT);
}
d=d>>1; // now the next bit is in the least sig bit position.
}
}//end OneWireOutByte
byte OneWireInByte(int Pin) // read byte, least sig byte first
{
byte d, n, b;
for (n=0; n<8; n++)
{
digitalWrite(Pin, LOW);
pinMode(Pin, OUTPUT);
delayMicroseconds(5);
pinMode(Pin, INPUT);
delayMicroseconds(5);
b = digitalRead(Pin);
delayMicroseconds(50);
d = (d >> 1) | (b<<7); // shift d to right and insert b in most sig bit position
}
return(d);
}//end OneWireInByte
void readTture(byte Pin){
//Pass WHICH pin you want to read in "Pin"
//Returns values in... (See global declarations)
OneWireReset(Pin);
OneWireOutByte(Pin, 0xcc);
OneWireOutByte(Pin, 0x44); // perform temperature conversion, strong pullup for one sec
OneWireReset(Pin);
OneWireOutByte(Pin, 0xcc);
OneWireOutByte(Pin, 0xbe);
LowByte = OneWireInByte(Pin);
HighByte = OneWireInByte(Pin);
TReading = (HighByte << 8) + LowByte;
SignBit = TReading & 0x8000; // test most sig bit
if (SignBit) // negative
{
TReading = (TReading ^ 0xffff) + 1; // 2's comp
}
Tc_100 = (6 * TReading) + TReading / 4; // multiply by (100 * 0.0625) or 6.25
Whole = Tc_100 / 100; // separate off the whole and fractional portions
Fract = Tc_100 % 100;
};//end readTture
void printTture(){//Uses values from global variables.
//See global declarations.
//N.B.: No new line inside printTture
myFile = SD.open("test.txt", FILE_WRITE); //+++++++++++++OPEN
if (SignBit) // If it's negative
{
Serial.print("-");
lcd.print("-");
myFile.print("-");
};
Serial.print(Whole);
Serial.print(".");
lcd.print(Whole);
lcd.print(".");
myFile.print(Whole);
myFile.print(".");
if (Fract < 10)
{
Serial.print("0");
lcd.print("0");
myFile.print("0");
};
Serial.print(Fract);
lcd.print(Fract);
myFile.print(Fract);
Serial.print(" ");
myFile.print(", ");
myFile.close();//++++++++++++++++++++++++ CLOSE
};//end printTture