DS1307 RTC conflicts with DS18B20

Question

I'm working on a project to output the temperature from a DS18B20 to a 16x2 LCD while logging the temperature to a CSV file using the Adafruit Data Logging Shield. I keep getting this error when verifying the code:

RTClib-master/RTClib.cpp.o: In function `RTC_DS1307::now()':
/Users/g/Documents/Arduino/libraries/RTClib-master/RTClib.cpp:252: undefined reference to 'Wire'
/Users/g/Documents/Arduino/libraries/RTClib-master/RTClib.cpp:252: undefined reference to 'Wire'
/Users/g/Documents/Arduino/libraries/RTClib-master/RTClib.cpp:252: undefined reference to 
'TwoWire::beginTransmission(int)'RTClib-master/RTClib.cpp.o: In function 'TwoWire::write(int)':
/Applications/Arduino.app/Contents/Resources/Java/libraries/Wire/Wire.h:72: undefined reference to 'TwoWire::write(unsigned char)'
RTClib-master/RTClib.cpp.o: In function 'RTC_DS1307::now()':
/Users/g/Documents/Arduino/libraries/RTClib-master/RTClib.cpp:254: undefined reference to 'TwoWire::endTransmission()'
/Users/g/Documents/Arduino/libraries/RTClib-master/RTClib.cpp:256: undefined reference to 'TwoWire::requestFrom(int, int)'
/Users/g/Documents/Arduino/libraries/RTClib-master/RTClib.cpp:257: undefined reference to 'TwoWire::read()'
/Users/g/Documents/Arduino/libraries/RTClib-master/RTClib.cpp:258: undefined reference to 'TwoWire::read()'
/Users/g/Documents/Arduino/libraries/RTClib-master/RTClib.cpp:259: undefined reference to 'TwoWire::read()'
/Users/g/Documents/Arduino/libraries/RTClib-master/RTClib.cpp:260: undefined reference to 'TwoWire::read()'
/Users/g/Documents/Arduino/libraries/RTClib-master/RTClib.cpp:261: undefined reference to 'TwoWire::read()' RTClib-master/RTClib.cpp.o:/Users/grafton/Documents/Arduino/libraries/RTClib-master/RTClib.cpp:262: more undefined references to 'TwoWire::read()' follow

When I comment RTC_DS1307 RTC; in the code (below) these errors go away, but of course I get errors related to an undefined RTC. I'm a newbie cobbling together code from various sources, so any help is greatly appreciated. Code follows:

#include <LiquidCrystal.h>
#include <OneWire.h>
#include <DallasTemperature.h>
#define ONE_WIRE_BUS 2
#include <SD.h>
#include "RTClib.h"
OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);
const int chipSelect = 10;
File tempLog;
RTC_DS1307 RTC;
LiquidCrystal lcd(6, 7, 8, 9, 11, 12);
void setup() { 
 Serial.begin(9600);
 while (!Serial) {
 ; 
 lcd.begin(16, 2);
 // ---------------- 
 lcd.print("Current temp (F)");
 sensors.begin();
 }
Serial.print("Initializing SD card...");
 pinMode(SS, OUTPUT);
 if (!SD.begin(chipSelect)) {
 Serial.println("Initialization failed!");
 while (1);
 }
 Serial.println("Initialization done.");
tempLog = SD.open("templog.txt", FILE_WRITE); 
if (! tempLog) {
 Serial.println("Error opening templog.txt");
 while(1);
}
char filename[] = "LOGGER00.CSV";
 for (uint8_t i = 0; i < 100; i++) {
 filename[6] = i/10 + '0';
 filename[7] = i%10 + '0';
 if (! SD.exists(filename)) {
 // only open a new file if it doesn't exist
 tempLog = SD.open(filename, FILE_WRITE);
 break; // leave the loop!
 }
 Serial.print("Writing to: ");
 Serial.println(filename);
 tempLog.println("Data Logging File");
 tempLog.println("Date,Temp(F)");
 } 
} 
void loop() {
 sensors.requestTemperatures();
 float temperature = sensors.getTempFByIndex(0);
 lcd.setCursor(6, 1);
 lcd.print(temperature);
 Serial.println(temperature);
 //-----------------------------------------------------------
String dataString = "";
//date time stuff-------------------------------------------
DateTime now = RTC.now();
 // log time
// tempLog.print(now.unixtime()); // seconds since 1/1/1970
// tempLog.print(", ");
 tempLog.print('"');
 tempLog.print(now.year(), DEC);
 tempLog.print("/");
 tempLog.print(now.month(), DEC);
 tempLog.print("/");
 tempLog.print(now.day(), DEC);
 tempLog.print(" ");
 tempLog.print(now.hour(), DEC);
 tempLog.print(":");
 tempLog.print(now.minute(), DEC);
 tempLog.print(":");
 tempLog.print(now.second(), DEC);
 tempLog.print('"');
 tempLog.print(",");
 tempLog.print(temperature);
 tempLog.print(",");
 delay(500);
tempLog.println(dataString);
tempLog.flush();
}

Answer 1

The RTC library requires the Wire library. Just put #include <Wire.h> in front of the line #include "RTClib.h"

• Zilliput: I have tried to simply #include <Wire.h> in RTClib.h, rather than putting #include <Wire.h> above #include "RTClib.h" in my sketch, but this does not work. Do you know why?
• Gerben: That indeed doesn't work. I don't know the reason; sorry.