https://github.com/JChristensen/DS3232RTC
ReadMe file
Jack Christensen Mar 2013
DS3232RTC is an Arduino library that supports the Maxim Integrated DS3232 and DS3231 Real-Time Clocks. This library is intended to be used with the Arduino Time library.
The DS3232RTC library is a drop-in replacement for the DS1307RTC.h library by Michael Margolis that is supplied with the Arduino Time library above. To change from using a DS1307 RTC to an DS323x RTC, it is only necessary to use #include <DS3232RTC.h>
instead of #include <DS1307RTC.h>
.
DS3232RTC also implements functions to support the additional features of the DS3232 and DS3231. The DS3231 has the same features as the DS3232 except: (1) Battery-backed SRAM, (2) Battery-backed 32kHz output (BB32kHz bit in Control/Status register 0x0F), and (3) Adjustable temperature sensor sample rate (CRATE1:0 bits in the Control/Status register).
"Arduino DS3232RTC Library" by Jack Christensen is licensed under CC BY-SA 4.0.
To use the DS3232RTC library:
- Go to https://github.com/JChristensen/DS3232RTC, click the Download ZIP button and save the ZIP file to a convenient location on your PC.
- Uncompress the downloaded file. This will result in a folder containing all the files for the library, that has a name that includes the branch name, usually DS3232RTC-master.
- Rename the folder to just DS3232RTC.
- Copy the renamed folder to the Arduino sketchbook\libraries folder.
The following example sketches are included with the DS3232RTC library:
- SetSerial: Set the RTC's date and time from the Arduino serial monitor. Displays date, time and temperature.
- TimeRTC: Same as the example of the same name provided with the Time library, demonstrating the interchangeability of the DS3232RTC library with the DS1307RTC library.
- tiny3232_KnockBang: Demonstrates interfacing an ATtiny45/85 to a DS3231 or DS3232 RTC.
When using the DS3232RTC library, the user is responsible for ensuring that reads and writes do not exceed the device's address space (0x00-0x12 for DS3231, 0x00-0xFF for DS3232); no bounds checking is done by the library.
Similar to the DS1307RTC library, the DS3232RTC library instantiates an RTC object; the user does not need to do this.
To use the DS3232RTC library, the Time and Wire libraries must also be included. For brevity, these includes are not repeated in the examples below:
#include <DS3232RTC.h> //http://github.com/JChristensen/DS3232RTC
#include <Time.h> //http://www.arduino.cc/playground/Code/Time
#include <Wire.h> //http://arduino.cc/en/Reference/Wire (included with Arduino IDE)
Symbolic names used with the squareWave() method (described below).
- SQWAVE_NONE
- SQWAVE_1_HZ
- SQWAVE_1024_HZ
- SQWAVE_4096_HZ
- SQWAVE_8192_HZ
Symbolic names used with the setAlarm() method (described below).
- ALM1_EVERY_SECOND -- causes an alarm once per second.
- ALM1_MATCH_SECONDS -- causes an alarm when the seconds match (i.e. once per minute).
- ALM1_MATCH_MINUTES -- causes an alarm when the minutes and seconds match.
- ALM1_MATCH_HOURS -- causes an alarm when the hours and minutes and seconds match.
- ALM1_MATCH_DATE -- causes an alarm when the date of the month and hours and minutes and seconds match.
- ALM1_MATCH_DAY -- causes an alarm when the day of the week and hours and minutes and seconds match.
- ALM2_EVERY_MINUTE -- causes an alarm once per minute.
- ALM2_MATCH_MINUTES -- causes an alarm when the minutes match (i.e. once per hour).
- ALM2_MATCH_HOURS -- causes an alarm when the hours and minutes match.
- ALM2_MATCH_DATE -- causes an alarm when the date of the month and hours and minutes match.
- ALM2_MATCH_DAY -- causes an alarm when the day of the week and hours and minutes match.
###get(void)
#####Description
Reads the current date and time from the RTC and returns it as a time_t value. Returns zero if an I2C error occurs (RTC not present, etc.).
#####Syntax
RTC.get();
#####Parameters
None.
#####Returns
Current date and time (time_t)
#####Example
time_t myTime;
myTime = RTC.get();
###set(time_t t)
#####Description
Sets the RTC date and time to the given time_t value.
#####Syntax
RTC.set(t);
#####Parameters
t: The date and time to set the RTC to (time_t)
#####Returns
I2C status (byte). Returns zero if successful.
#####Example
//this example first sets the system time (maintained by the Time library) to
//a hard-coded date and time, and then sets the RTC from the system time.
//the setTime() function is part of the Time library.
setTime(23, 31, 30, 13, 2, 2009); //set the system time to 23h31m30s on 13Feb2009
RTC.set(now()); //set the RTC from the system time
###read(tmElements_t &tm)
#####Description
Reads the current date and time from the RTC and returns it as a tmElements_t structure. See the Arduino Time library for details on the tmElements_t structure.
#####Syntax
RTC.read(tm);
#####Parameters
tm: Address of a tmElements_t structure to which the date and time are returned.
#####Returns
I2C status (byte). Returns zero if successful. The date and time read from the RTC are returned to the tm parameter.
#####Example
tmElements_t tm;
RTC.read(tm);
Serial.print(tm.Hour, DEC);
Serial.print(':');
Serial.print(tm.Minute,DEC);
Serial.print(':');
Serial.println(tm.Second,DEC);
###write(tmElements_t &tm)
#####Description
Sets the RTC to the date and time given by a tmElements_t structure.
#####Syntax
RTC.write(tm);
#####Parameters
tm: Address of a tmElements_t structure used to set the date and time.
#####Returns
I2C status (byte). Returns zero if successful.
#####Example
tmElements_t tm;
tm.Hour = 23; //set the tm structure to 23h31m30s on 13Feb2009
tm.Minute = 31;
tm.Minute = 30;
tm.Day = 13;
tm.Month = 2;
tm.Year = 2009 - 1970; //tmElements_t.Year is the offset from 1970
RTC.write(tm); //set the RTC from the tm structure
The DS3232RTC.h file defines symbolic names for the timekeeping, alarm, status and control registers. These can be used for the addr argument in the functions below.
###writeRTC(byte addr, byte *values, byte nBytes)
#####Description
Write one or more bytes to RTC memory.
#####Syntax
RTC.writeRTC(addr, values, nbytes);
#####Parameters
addr: First SRAM address to write (byte). The valid address range is 0x00-0x12 for DS3231, 0x00-0xFF for DS3232. The general-purpose SRAM for the DS3232 begins at address 0x14. Address is not checked for validity by the library.
values: An array of values to write (*byte)
nBytes: Number of bytes to write (byte). Must be between 1 and 31 (Wire library limitation) but is not checked by the library.
#####Returns
I2C status (byte). Returns zero if successful.
#####Example
//write 1, 2, ..., 8 to the first eight DS3232 SRAM locations
byte buf[8] = {1, 2, 3, 4, 5, 6, 7, 8};
RTC.sramWrite(0x14, buf, 8);
###writeRTC(byte addr, byte value)
#####Description
Write a single byte to RTC memory.
#####Syntax
RTC.writeRTC(addr, value);
#####Parameters
addr: SRAM address to write (byte). The valid address range is 0x00-0x12 for DS3231, 0x00-0xFF for DS3232. The general-purpose SRAM for the DS3232 begins at address 0x14. Address is not checked for validity by the library.
value: Value to write (byte)
#####Returns
I2C status (byte). Returns zero if successful.
#####Example
RTC.writeRTC(3, 14); //write the value 14 to SRAM address 3
###readRTC(byte addr, byte *values, byte nBytes)
#####Description
Read one or more bytes from RTC RAM.
#####Syntax
RTC.readRTC(addr, values, nbytes);
#####Parameters
addr: First SRAM address to read (byte). The valid address range is 0x00-0x12 for DS3231, 0x00-0xFF for DS3232. The general-purpose SRAM for the DS3232 begins at address 0x14. Address is not checked for validity by the library.
values: An array to receive the values read (*byte)
nBytes: Number of bytes to read (byte). Must be between 1 and 32 (Wire library limitation) but is not checked by the library.
#####Returns
I2C status (byte). Returns zero if successful.
#####Example
//read the last eight locations of SRAM into buf
byte buf[8];
RTC.sramRead(248, buf, 8);
###readRTC(byte addr)
#####Description
Reads a single byte from RTC RAM.
#####Syntax
RTC.readRTC(addr);
#####Parameters
addr: SRAM address to read (byte). The valid address range is 0x00-0x12 for DS3231, 0x00-0xFF for DS3232. The general-purpose SRAM for the DS3232 begins at address 0x14. Address is not checked for validity by the library.
#####Returns
Value read from the RTC (byte)
#####Example
byte val;
val = RTC.readRTC(3); //read the value from SRAM location 3
The DS3232 and DS3231 have two alarms. Alarm1 can be set to seconds precision; Alarm2 can only be set to minutes precision.
###setAlarm(ALARM_TYPES_t alarmType, byte seconds, byte minutes, byte hours, byte daydate) #####Description Set an alarm time. Sets the alarm registers only. To cause the INT pin to be asserted on alarm match, use alarmInterrupt(). This method can set either Alarm 1 or Alarm 2, depending on the value of alarmType (use the ALARM_TYPES_t enumeration above). When setting Alarm 2, the seconds value must be supplied but is ignored, recommend using zero. (Alarm 2 has no seconds register.)
#####Syntax
RTC.setAlarm(alarmType, seconds, minutes, hours, dayOrDate);
#####Parameters
alarmType: A value from the ALARM_TYPES_t enumeration, above. (ALARM_TYPES_t)
seconds: The seconds value to set the alarm to. (byte)
minutes: The minutes value to set the alarm to. (byte)
hours: The hours value to set the alarm to. (byte)
dayOrDate: The day of the week or the date of the month. For day of the week, use a value from the Time library timeDayOfWeek_t enumeration, i.e. dowSunday, dowMonday, dowTuesday, dowWednesday, dowThursday, dowFriday, dowSaturday. (byte)
#####Returns
None.
#####Example
//Set Alarm1 for 12:34:56 on Sunday
RTC.setAlarm(ALM1_MATCH_DAY, 56, 34, 12, dowSunday);
###setAlarm(ALARM_TYPES_t alarmType, byte minutes, byte hours, byte daydate) #####Description Set an alarm time. Sets the alarm registers only. To cause the INT pin to be asserted on alarm match, use alarmInterrupt(). This method can set either Alarm 1 or Alarm 2, depending on the value of alarmType (use the ALARM_TYPES_t enumeration above). However, when using this method to set Alarm 1, the seconds value is set to zero. (Alarm 2 has no seconds register.)
#####Syntax
RTC.setAlarm(alarmType, minutes, hours, dayOrDate);
#####Parameters
alarmType: A value from the ALARM_TYPES_t enumeration, above. (ALARM_TYPES_t)
minutes: The minutes value to set the alarm to. (byte)
hours: The hours value to set the alarm to. (byte)
dayOrDate: The day of the week or the date of the month. For day of the week, use a value from the Time library timeDayOfWeek_t enumeration, i.e. dowSunday, dowMonday, dowTuesday, dowWednesday, dowThursday, dowFriday, dowSaturday. (byte)
#####Returns
None.
#####Example
//Set Alarm2 for 12:34 on the 4th day of the month
RTC.setAlarm(ALM1_MATCH_DATE, 34, 12, 4);
###alarmInterrupt(byte alarmNumber, boolean alarmEnabled)
#####Description
Enable or disable an alarm "interrupt". Note that this "interrupt" causes the RTC's INT pin to be asserted. To use this signal as an actual interrupt to a microcontroller, it will need to be connected properly and programmed in the application firmware.
on the RTC.
#####Syntax
RTC.alarmInterrupt(alarmNumber, enable);
#####Parameters
alarmNumber: The number of the alarm to enable or disable, ALARM_1 or ALARM_2 (byte)
alarmEnabled: true or false (boolean)
#####Returns
None.
#####Example
RTC.alarmInterrupt(ALARM_1, true); //assert the INT pin when Alarm1 occurs.
RTC.alarmInterrupt(ALARM_2, false); //disable Alarm2
###alarm(byte alarmNumber)
#####Description
Tests whether an alarm has been triggered. If the alarm was triggered, returns true and resets the alarm flag in the RTC, else returns false.
#####Syntax
RTC.alarm(alarmNumber);
#####Parameters
alarmNumber: The number of the alarm to test, ALARM_1 or ALARM_2 (byte)
#####Returns
Description (type)
#####Example
if ( RTC.alarm(ALARM_1) ) { //has Alarm1 triggered?
//yes, act on the alarm
}
else {
//no alarm
}
###temperature(void)
#####Description
Returns the RTC temperature.
#####Syntax
RTC.temperature();
#####Parameters
None.
#####Returns
RTC temperature as degrees Celsius times four. (int)
#####Example
int t = RTC.temperature();
float celsius = t / 4.0;
float fahrenheit = celsius * 9.0 / 5.0 + 32.0;
###squareWave(SQWAVE_FREQS_t freq)
#####Description
Enables or disables the square wave output.
#####Syntax
RTC.squareWave(freq);
#####Parameters
freq: a value from the SQWAVE_FREQS_t enumeration above. (SQWAVE_FREQS_t)
#####Returns
None.
#####Example
RTC.squareWave(SQWAVE_1_HZ); //1 Hz square wave
RTC.squareWave(SQWAVE_NONE); //no square wave
###oscStopped(void)
#####Description
Check whether the RTC oscillator is or was stopped. This may indicate that the RTC's time is not accurate.
#####Syntax
RTC.oscStopped();
#####Parameters
None.
#####Returns
True or false (boolean)
#####Example
if ( RTC.oscStopped() ) { //check the oscillator
//may be trouble
}
else {
//all is well
}