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Readme file for Arduino Time Library # Arduino Time Library
Time is a library that provides timekeeping functionality for Arduino. Time is a library that provides timekeeping functionality for Arduino.
...@@ -12,8 +12,11 @@ Example sketches illustrate how similar sketch code can be used with: a Real Tim ...@@ -12,8 +12,11 @@ Example sketches illustrate how similar sketch code can be used with: a Real Tim
internet NTP time service, GPS time data, and Serial time messages from a computer internet NTP time service, GPS time data, and Serial time messages from a computer
for time synchronization. for time synchronization.
The functions available in the library include: ## Functionality
The functions available in the library include
```c
hour(); // the hour now (0-23) hour(); // the hour now (0-23)
minute(); // the minute now (0-59) minute(); // the minute now (0-59)
second(); // the second now (0-59) second(); // the second now (0-59)
...@@ -21,115 +24,132 @@ day(); // the day now (1-31) ...@@ -21,115 +24,132 @@ day(); // the day now (1-31)
weekday(); // day of the week (1-7), Sunday is day 1 weekday(); // day of the week (1-7), Sunday is day 1
month(); // the month now (1-12) month(); // the month now (1-12)
year(); // the full four digit year: (2009, 2010 etc) year(); // the full four digit year: (2009, 2010 etc)
```
there are also functions to return the hour in 12 hour format there are also functions to return the hour in 12 hour format
```c
hourFormat12(); // the hour now in 12 hour format hourFormat12(); // the hour now in 12 hour format
isAM(); // returns true if time now is AM isAM(); // returns true if time now is AM
isPM(); // returns true if time now is PM isPM(); // returns true if time now is PM
now(); // returns the current time as seconds since Jan 1 1970 now(); // returns the current time as seconds since Jan 1 1970
```
The time and date functions can take an optional parameter for the time. This prevents The time and date functions can take an optional parameter for the time. This prevents
errors if the time rolls over between elements. For example, if a new minute begins errors if the time rolls over between elements. For example, if a new minute begins
between getting the minute and second, the values will be inconsistent. Using the between getting the minute and second, the values will be inconsistent. Using the
following functions eliminates this probglem following functions eliminates this probglem
time_t t = now(); // store the current time in time variable t
hour(t); // returns the hour for the given time t
minute(t); // returns the minute for the given time t
second(t); // returns the second for the given time t
day(t); // the day for the given time t
weekday(t); // day of the week for the given time t
month(t); // the month for the given time t
year(t); // the year for the given time t
```c
time_t t = now(); // store the current time in time variable t
hour(t); // returns the hour for the given time t
minute(t); // returns the minute for the given time t
second(t); // returns the second for the given time t
day(t); // the day for the given time t
weekday(t); // day of the week for the given time t
month(t); // the month for the given time t
year(t); // the year for the given time t
```
Functions for managing the timer services are: Functions for managing the timer services are:
setTime(t); // set the system time to the give time t ```c
setTime(hr,min,sec,day,mnth,yr); // alternative to above, yr is 2 or 4 digit yr setTime(t); // set the system time to the give time t
// (2010 or 10 sets year to 2010) setTime(hr,min,sec,day,mnth,yr); // alternative to above, yr is 2 or 4 digit yr
adjustTime(adjustment); // adjust system time by adding the adjustment value // (2010 or 10 sets year to 2010)
timeStatus(); // indicates if time has been set and recently synchronized adjustTime(adjustment); // adjust system time by adding the adjustment value
// returns one of the following enumerations: timeStatus(); // indicates if time has been set and recently synchronized
timeNotSet // the time has never been set, the clock started at Jan 1 1970 // returns one of the following enumerations:
timeNeedsSync // the time had been set but a sync attempt did not succeed timeNotSet // the time has never been set, the clock started at Jan 1 1970
timeSet // the time is set and is synced timeNeedsSync // the time had been set but a sync attempt did not succeed
timeSet // the time is set and is synced
```
Time and Date values are not valid if the status is timeNotSet. Otherwise values can be used but Time and Date values are not valid if the status is timeNotSet. Otherwise values can be used but
the returned time may have drifted if the status is timeNeedsSync. the returned time may have drifted if the status is timeNeedsSync.
setSyncProvider(getTimeFunction); // set the external time provider ```c
setSyncInterval(interval); // set the number of seconds between re-sync setSyncProvider(getTimeFunction); // set the external time provider
setSyncInterval(interval); // set the number of seconds between re-sync
```
There are many convenience macros in the `time.h` file for time constants and conversion
There are many convenience macros in the time.h file for time constants and conversion
of time units. of time units.
To use the library, copy the download to the Library directory. To use the library, copy the download to the Library directory.
## Examples
The Time directory contains the Time library and some example sketches The Time directory contains the Time library and some example sketches
illustrating how the library can be used with various time sources: illustrating how the library can be used with various time sources:
- TimeSerial.pde shows Arduino as a clock without external hardware. - `TimeSerial.pde` shows Arduino as a clock without external hardware.
It is synchronized by time messages sent over the serial port. It is synchronized by time messages sent over the serial port.
A companion Processing sketch will automatically provide these messages A companion Processing sketch will automatically provide these messages
if it is running and connected to the Arduino serial port. if it is running and connected to the Arduino serial port.
- TimeSerialDateStrings.pde adds day and month name strings to the sketch above - `TimeSerialDateStrings.pde` adds day and month name strings to the sketch above
Short (3 character) and long strings are available to print the days of Short (3 character) and long strings are available to print the days of
the week and names of the months. the week and names of the months.
- TimeRTC uses a DS1307 real time clock to provide time synchronization. - `TimeRTC` uses a DS1307 real time clock to provide time synchronization.
A basic RTC library named DS1307RTC is included in the download. A basic RTC library named DS1307RTC is included in the download.
To run this sketch the DS1307RTC library must be installed. To run this sketch the DS1307RTC library must be installed.
- TimeRTCSet is similar to the above and adds the ability to set the Real Time Clock - `TimeRTCSet` is similar to the above and adds the ability to set the Real Time Clock
- TimeRTCLog demonstrates how to calculate the difference between times. - `TimeRTCLog` demonstrates how to calculate the difference between times.
It is a vary simple logger application that monitors events on digtial pins It is a vary simple logger application that monitors events on digtial pins
and prints (to the serial port) the time of an event and the time period since and prints (to the serial port) the time of an event and the time period since
the previous event. the previous event.
- TimeNTP uses the Arduino Ethernet shield to access time using the internet NTP time service. - `TimeNTP` uses the Arduino Ethernet shield to access time using the internet NTP time service.
The NTP protocol uses UDP and the UdpBytewise library is required, see: The NTP protocol uses UDP and the UdpBytewise library is required, see:
http://bitbucket.org/bjoern/arduino_osc/src/14667490521f/libraries/Ethernet/ http://bitbucket.org/bjoern/arduino_osc/src/14667490521f/libraries/Ethernet/
- TimeGPS gets time from a GPS - `TimeGPS` gets time from a GPS
This requires the TinyGPS library from Mikal Hart: This requires the TinyGPS library from Mikal Hart:
http://arduiniana.org/libraries/TinyGPS http://arduiniana.org/libraries/TinyGPS
## Differences
Differences between this code and the playground DateTime library Differences between this code and the playground DateTime library
although the Time library is based on the DateTime codebase, the API has changed. although the Time library is based on the DateTime codebase, the API has changed.
Changes in the Time library API: Changes in the Time library API:
- time elements are functions returning int (they are variables in DateTime)
- time elements are functions returning `int` (they are variables in DateTime)
- Years start from 1970 - Years start from 1970
- days of the week and months start from 1 (they start from 0 in DateTime) - days of the week and months start from 1 (they start from 0 in DateTime)
- DateStrings do not require a seperate library - DateStrings do not require a seperate library
- time elements can be accessed non-atomically (in DateTime they are always atomic) - time elements can be accessed non-atomically (in DateTime they are always atomic)
- function added to automatically sync time with extrnal source - function added to automatically sync time with extrnal source
- localTime and maketime parameters changed, localTime renamed to breakTime - `localTime` and `maketime` parameters changed, `localTime` renamed to `breakTime`
Technical notes: ## Technical notes:
Internal system time is based on the standard Unix time_t. Internal system time is based on the standard Unix `time_t`.
The value is the number of seconds since Jan 1 1970. The value is the number of seconds since Jan 1 1970.
System time begins at zero when the sketch starts. System time begins at zero when the sketch starts.
The internal time can be automatically synchronized at regular intervals to an external time source. The internal time can be automatically synchronized at regular intervals to an external time source.
This is enabled by calling the setSyncProvider(provider) function - the provider argument is This is enabled by calling the `setSyncProvider(provider)` function - the provider argument is
the address of a function that returns the current time as a time_t. the address of a function that returns the current time as a `time_t`.
See the sketches in the examples directory for usage. See the sketches in the examples directory for usage.
The default interval for re-syncing the time is 5 minutes but can be changed by calling the The default interval for re-syncing the time is 5 minutes but can be changed by calling the
setSyncInterval( interval) method to set the number of seconds between re-sync attempts. `setSyncInterval(interval)` method to set the number of seconds between re-sync attempts.
The Time library defines a structure for holding time elements that is a compact version of the C tm structure. The Time library defines a structure for holding time elements that is a compact version of the C tm structure.
All the members of the Arduino tm structure are bytes and the year is offset from 1970. All the members of the Arduino tm structure are bytes and the year is offset from 1970.
Convenience macros provide conversion to and from the Arduino format. Convenience macros provide conversion to and from the Arduino format.
Low level functions to convert between system time and individual time elements are provided: Low level functions to convert between system time and individual time elements are provided:
breakTime(time, &tm); // break time_t into elements stored in tm struct
makeTime(&tm); // return time_t from elements stored in tm struct ```c
breakTime(time, &tm); // break time_t into elements stored in tm struct
makeTime(&tm); // return time_t from elements stored in tm struct
```
The DS1307RTC library included in the download provides an example of how a time provider The DS1307RTC library included in the download provides an example of how a time provider
can use the low level functions to interface with the Time library. can use the low level functions to interface with the Time library.
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