Added vbaten() method to set or clear the VBATEN bit in the day register (0x03).

JChristensen · JChristensen · commit 10194da24bf7 · 2013-08-21T18:22:12.000-04:00
Added sketch to demonstrate interfacing the MCP79412 to an ATtiny45/85.
diff --git a/Examples/tiny79412_KnockBang/tiny79412_KnockBang.ino b/Examples/tiny79412_KnockBang/tiny79412_KnockBang.ino
@@ -0,0 +1,86 @@
+/*----------------------------------------------------------------------*
+ * Digital clock display using an MCP79412 Real-Time Clock/Calendar     *
+ * and an ATtiny45/85 with a 1MHz system clock.                         *
+ *                                                                      *
+ * Tested with Arduino 1.0.5. Also Arduino-Tiny Core, TinyISP, and      *
+ * TinyDebugKnockBang from http://code.google.com/p/arduino-tiny/       *
+ *                                                                      *
+ * Run TinyISP on an ATmega microcontroller that does not have an LED   *
+ * connected to pin 13 (SCK). The LED causes problems because the SPI   *
+ * pins are also the I2C pins on the ATtiny. Connect MISO, MOSI, SCK    *
+ * on the ATmega to the corresponding pins on the ATtiny through 220Ω   *
+ * resistors for safety. Use 4.7K pullup resistors on the ATtiny        *    
+ * I2C bus.                                                             *
+ *                                                                      *
+ * Jack Christensen 21Aug2013                                           *
+ *                                                                      *
+ * This work is licensed under the Creative Commons Attribution-        *
+ * ShareAlike 3.0 Unported License. To view a copy of this license,     *
+ * visit http://creativecommons.org/licenses/by-sa/3.0/ or send a       *
+ * letter to Creative Commons, 171 Second Street, Suite 300,            *
+ * San Francisco, California, 94105, USA.                               *
+ *----------------------------------------------------------------------*/ 
+
+#include <MCP79412RTC.h>           //http://github.com/JChristensen/MCP79412RTC
+#include <Time.h>                  //http://playground.arduino.cc/Code/Time
+#include <TinyDebugKnockBang.h>    //http://code.google.com/p/arduino-tiny/
+#include <TinyWireM.h>             //http://playground.arduino.cc/Code/USIi2c
+
+void setup(void)
+{
+    Debug.begin(250000);
+    
+    //setSyncProvider() causes the Time library to synchronize with the
+    //external RTC by calling RTC.get() every five minutes by default.
+    setSyncProvider(RTC.get);
+    Debug.print(F("RTC Sync"));
+    if (timeStatus() != timeSet) Debug.print(F(" FAIL!"));
+    Debug.println();
+}
+
+void loop(void)
+{
+    static time_t tLast;
+
+    time_t t = now();
+    if (t != tLast) {
+        tLast = t;
+        printDateTime(t);
+        Debug.println();
+    }
+}
+
+//print date and time to Serial
+void printDateTime(time_t t)
+{
+    printDate(t);
+    Debug.print(' ');
+    printTime(t);
+}
+
+//print time to Serial
+void printTime(time_t t)
+{
+    printI00(hour(t), ':');
+    printI00(minute(t), ':');
+    printI00(second(t), ' ');
+}
+
+//print date to Serial
+void printDate(time_t t)
+{
+    printI00(day(t), 0);
+    Debug.print(monthShortStr(month(t)));
+    Debug.print(year(t), DEC);
+}
+
+//Print an integer in "00" format (with leading zero),
+//followed by a delimiter character to Serial.
+//Input value assumed to be between 0 and 99.
+void printI00(int val, char delim)
+{
+    if (val < 10) Debug.print('0');
+    Debug.print(val, DEC);;
+    if (delim > 0) Debug.print(delim);
+    return;
+}
diff --git a/MCP79412RTC.cpp b/MCP79412RTC.cpp
@@ -559,6 +559,25 @@ boolean MCP79412RTC::isRunning(void)
     return i2cRead() & _BV(ST);
 }
 
+/*----------------------------------------------------------------------*
+ * Set or clear the VBATEN bit. Setting the bit powers the clock and    *
+ * SRAM from the backup battery when Vcc falls. Note that setting the   *
+ * time via set() or write() sets the VBATEN bit.                       *
+ *----------------------------------------------------------------------*/
+void MCP79412RTC::vbaten(boolean enable)
+{
+    uint8_t day;
+    
+    ramRead(DAY_REG, &day, 1);
+    if (enable)
+        day |= _BV(VBATEN);
+    else
+        day &= ~_BV(VBATEN);
+        
+    ramWrite(DAY_REG, &day, 1);
+    return;
+}
+
 /*----------------------------------------------------------------------*
  * Decimal-to-BCD conversion                                            *
  *----------------------------------------------------------------------*/
diff --git a/MCP79412RTC.h b/MCP79412RTC.h
@@ -138,6 +138,7 @@ class MCP79412RTC
         void out(boolean level);
         void alarmPolarity(boolean polarity);
         boolean isRunning(void);
+        void vbaten(boolean enable);
 
     private:
         static void ramWrite(byte addr, byte value);
diff --git a/ReadMe.txt b/ReadMe.txt
@@ -50,6 +50,9 @@ logger using the MCP79412RTC's ability to capture power down and power up times.
 Power failure events are logged to the MCP79412RTC's SRAM. Output is to the
 Arduino serial monitor.
 
+tiny79412_KnockBang: Demonstrates interfacing an ATtiny45/85 to the
+MCP79412.
+
 --------------------------------------------------------------------------------
 Similar to the DS1307RTC library, the MCP79412 library instantiates an RTC
 object; the user does not need to do this.
