Reading the temperature from a DS3232 chip

libraries/RTC/DS3232RTC.cpp

@@ -353,6 +353,16 @@ void DS3232RTC::writeByte(uint8_t offset, uint8_t value)
         RTC::writeByte(offset, value);
 }
 
+int DS3232RTC::readTemperature()
+{
+    if (_isRealTime) {
+        return (((int)(signed char)readRegister(DS3232_TEMP_MSB)) << 2) |
+               (readRegister(DS3232_TEMP_LSB) >> 6);
+    } else {
+        return NO_TEMPERATURE;
+    }
+}
+
 /**
  * \brief Enables the generation of interrupts for alarms 0 and 1.
  *

libraries/RTC/DS3232RTC.h

@@ -48,6 +48,8 @@ public:
     uint8_t readByte(uint8_t offset);
     void writeByte(uint8_t offset, uint8_t value);
 
+    int readTemperature();
+
     void enableAlarmInterrupts();
     void disableAlarmInterrupts();
     int firedAlarm();

libraries/RTC/RTC.cpp

@@ -257,6 +257,24 @@ void RTC::writeByte(uint8_t offset, uint8_t value)
     }
 }
 
+/**
+ * \var RTC::NO_TEMPERATURE
+ * \brief Value that is returned from readTemperature() if the realtime
+ * clock chip cannot determine the temperature.
+ */
+
+/**
+ * \brief Reads the value of the temperature sensor and returns the
+ * temperature in quarters of a degree celcius.
+ *
+ * Returns the value NO_TEMPERATURE if the realtime clock chip cannot
+ * determine the temperature.
+ */
+int RTC::readTemperature()
+{
+    return NO_TEMPERATURE;
+}
+
 /**
  * \var RTC::INCREMENT
  * \brief Increment the day, month, or year in a call to adjustDays(), adjustMonths(), or adjustYears().

libraries/RTC/RTC.h

@@ -69,6 +69,10 @@ public:
     virtual uint8_t readByte(uint8_t offset);
     virtual void writeByte(uint8_t offset, uint8_t value);
 
+    static const int NO_TEMPERATURE = 32767;
+
+    virtual int readTemperature();
+
     // Flags for adjustDays(), adjustMonths(), and adjustYears().
     static const uint8_t INCREMENT = 0x0000;
     static const uint8_t DECREMENT = 0x0001;

libraries/RTC/examples/DumpRTC/DumpRTC.pde

@@ -0,0 +1,78 @@
+/*
+This example demonstrates how to read time, date, and other information
+from the DS3232 realtime clock chip.
+
+This example is placed into the public domain.
+*/
+
+#include <SoftI2C.h>
+#include <DS3232RTC.h>
+
+SoftI2C i2c(A4, A5);
+DS3232RTC rtc(i2c);
+
+const char *months[] = {
+    " Jan ", " Feb ", " Mar ", " Apr ", " May ", " Jun ",
+    " Jul ", " Aug ", " Sep ", " Oct ", " Nov ", " Dec "
+};
+
+void setup() {
+    Serial.begin(9600);
+
+    RTCAlarm alarm;
+    for (byte alarmNum = 0; alarmNum < RTC::ALARM_COUNT; ++alarmNum) {
+        rtc.readAlarm(alarmNum, &alarm);
+        Serial.print("Alarm ");
+        Serial.print(alarmNum + 1, DEC);
+        Serial.print(": ");
+        if (alarm.flags & 0x01) {
+            printDec2(alarm.hour);
+            Serial.print(':');
+            printDec2(alarm.minute);
+            Serial.println();
+        } else {
+            Serial.println("Off");
+        }
+    }
+    Serial.println();
+}
+
+void loop() {
+    RTCTime time;
+    RTCDate date;
+    rtc.readTime(&time);
+    rtc.readDate(&date);
+
+    Serial.print("Time: ");
+    printDec2(time.hour);
+    Serial.print(':');
+    printDec2(time.minute);
+    Serial.print(':');
+    printDec2(time.second);
+    Serial.println();
+
+    Serial.print("Date: ");
+    Serial.print(date.day, DEC);
+    Serial.print(months[date.month - 1]);
+    Serial.print(date.year);
+    Serial.println();
+
+    Serial.print("Temp: ");
+    int temp = rtc.readTemperature();
+    if (temp != RTC::NO_TEMPERATURE) {
+        Serial.print(temp / 4.0);
+        Serial.println(" celcius");
+    } else {
+        Serial.println("not available");
+    }
+
+    Serial.println();
+
+    delay(1000);
+}
+
+void printDec2(int value)
+{
+    Serial.print((char)('0' + (value / 10)));
+    Serial.print((char)('0' + (value % 10)));
+}