Python - Real-Time Clock Bricklet

This is the description of the Python API bindings for the Real-Time Clock Bricklet. General information and technical specifications for the Real-Time Clock Bricklet are summarized in its hardware description.

An installation guide for the Python API bindings is part of their general description.

Examples

The example code below is Public Domain (CC0 1.0).

Simple

Download (example_simple.py)

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#!/usr/bin/env python
# -*- coding: utf-8 -*-

HOST = "localhost"
PORT = 4223
UID = "XYZ" # Change XYZ to the UID of your Real-Time Clock Bricklet

from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_real_time_clock import BrickletRealTimeClock

if __name__ == "__main__":
    ipcon = IPConnection() # Create IP connection
    rtc = BrickletRealTimeClock(UID, ipcon) # Create device object

    ipcon.connect(HOST, PORT) # Connect to brickd
    # Don't use device before ipcon is connected

    # Get current date and time
    year, month, day, hour, minute, second, centisecond, weekday = rtc.get_date_time()

    print("Year: " + str(year))
    print("Month: " + str(month))
    print("Day: " + str(day))
    print("Hour: " + str(hour))
    print("Minute: " + str(minute))
    print("Second: " + str(second))
    print("Centisecond: " + str(centisecond))
    print("Weekday: " + str(weekday))

    # Get current timestamp
    timestamp = rtc.get_timestamp()
    print("Timestamp: " + str(timestamp) + " ms")

    raw_input("Press key to exit\n") # Use input() in Python 3
    ipcon.disconnect()

Callback

Download (example_callback.py)

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#!/usr/bin/env python
# -*- coding: utf-8 -*-

HOST = "localhost"
PORT = 4223
UID = "XYZ" # Change XYZ to the UID of your Real-Time Clock Bricklet

from tinkerforge.ip_connection import IPConnection
from tinkerforge.bricklet_real_time_clock import BrickletRealTimeClock

# Callback function for date and time callback
def cb_date_time(year, month, day, hour, minute, second, centisecond, weekday, timestamp):
    print("Year: " + str(year))
    print("Month: " + str(month))
    print("Day: " + str(day))
    print("Hour: " + str(hour))
    print("Minute: " + str(minute))
    print("Second: " + str(second))
    print("Centisecond: " + str(centisecond))
    print("Weekday: " + str(weekday))
    print("Timestamp: " + str(timestamp))
    print("")

if __name__ == "__main__":
    ipcon = IPConnection() # Create IP connection
    rtc = BrickletRealTimeClock(UID, ipcon) # Create device object

    ipcon.connect(HOST, PORT) # Connect to brickd
    # Don't use device before ipcon is connected

    # Register date and time callback to function cb_date_time
    rtc.register_callback(rtc.CALLBACK_DATE_TIME, cb_date_time)

    # Set period for date and time callback to 5s (5000ms)
    # Note: The date and time callback is only called every 5 seconds
    #       if the date and time has changed since the last call!
    rtc.set_date_time_callback_period(5000)

    raw_input("Press key to exit\n") # Use input() in Python 3
    ipcon.disconnect()

API

Generally, every method of the Python bindings can throw an tinkerforge.ip_connection.Error exception that has a value and a description property. value can have different values:

  • Error.TIMEOUT = -1
  • Error.ALREADY_CONNECTED = -7
  • Error.NOT_CONNECTED = -8
  • Error.INVALID_PARAMETER = -9
  • Error.NOT_SUPPORTED = -10
  • Error.UNKNOWN_ERROR_CODE = -11
  • Error.STREAM_OUT_OF_SYNC = -12

All methods listed below are thread-safe.

Basic Functions

BrickletRealTimeClock(uid, ipcon)
Parameters:
  • uid -- string
  • ipcon -- IPConnection

Creates an object with the unique device ID uid:

real_time_clock = BrickletRealTimeClock("YOUR_DEVICE_UID", ipcon)

This object can then be used after the IP Connection is connected (see examples above).

BrickletRealTimeClock.set_date_time(year, month, day, hour, minute, second, centisecond, weekday)
Parameters:
  • year -- int
  • month -- int
  • day -- int
  • hour -- int
  • minute -- int
  • second -- int
  • centisecond -- int
  • weekday -- int
Return type:

None

Sets the current date (including weekday) and the current time with hundredths of a second resolution.

Possible value ranges:

  • Year: 2000 to 2099
  • Month: 1 to 12 (January to December)
  • Day: 1 to 31
  • Hour: 0 to 23
  • Minute: 0 to 59
  • Second: 0 to 59
  • Centisecond: 0 to 99
  • Weekday: 1 to 7 (Monday to Sunday)

If the backup battery is installed then the real-time clock keeps date and time even if the Bricklet is not powered by a Brick.

The real-time clock handles leap year and inserts the 29th of February accordingly. But leap seconds, time zones and daylight saving time are not handled.

The following constants are available for this function:

  • BrickletRealTimeClock.WEEKDAY_MONDAY = 1
  • BrickletRealTimeClock.WEEKDAY_TUESDAY = 2
  • BrickletRealTimeClock.WEEKDAY_WEDNESDAY = 3
  • BrickletRealTimeClock.WEEKDAY_THURSDAY = 4
  • BrickletRealTimeClock.WEEKDAY_FRIDAY = 5
  • BrickletRealTimeClock.WEEKDAY_SATURDAY = 6
  • BrickletRealTimeClock.WEEKDAY_SUNDAY = 7
BrickletRealTimeClock.get_date_time()
Return type:(int, int, int, int, int, int, int, int)

Returns the current date (including weekday) and the current time of the real-time clock with hundredths of a second resolution.

The following constants are available for this function:

  • BrickletRealTimeClock.WEEKDAY_MONDAY = 1
  • BrickletRealTimeClock.WEEKDAY_TUESDAY = 2
  • BrickletRealTimeClock.WEEKDAY_WEDNESDAY = 3
  • BrickletRealTimeClock.WEEKDAY_THURSDAY = 4
  • BrickletRealTimeClock.WEEKDAY_FRIDAY = 5
  • BrickletRealTimeClock.WEEKDAY_SATURDAY = 6
  • BrickletRealTimeClock.WEEKDAY_SUNDAY = 7

The returned namedtuple has the variables year, month, day, hour, minute, second, centisecond and weekday.

BrickletRealTimeClock.get_timestamp()
Return type:int

Returns the current date and the time of the real-time clock converted to milliseconds. The timestamp has an effective resolution of hundredths of a second.

Advanced Functions

BrickletRealTimeClock.set_offset(offset)
Parameters:offset -- int
Return type:None

Sets the offset the real-time clock should compensate for in 2.17 ppm steps between -277.76 ppm (-128) and +275.59 ppm (127).

The real-time clock time can deviate from the actual time due to the frequency deviation of its 32.768 kHz crystal. Even without compensation (factory default) the resulting time deviation should be at most ±20 ppm (±52.6 seconds per month).

This deviation can be calculated by comparing the same duration measured by the real-time clock (rtc_duration) an accurate reference clock (ref_duration).

For best results the configured offset should be set to 0 ppm first and then a duration of at least 6 hours should be measured.

The new offset (new_offset) can be calculated from the currently configured offset (current_offset) and the measured durations as follow:

new_offset = current_offset - round(1000000 * (rtc_duration - ref_duration) / rtc_duration / 2.17)

If you want to calculate the offset, then we recommend using the calibration dialog in Brick Viewer, instead of doing it manually.

The offset is saved in the EEPROM of the Bricklet and only needs to be configured once.

BrickletRealTimeClock.get_offset()
Return type:int

Returns the offset as set by set_offset().

BrickletRealTimeClock.get_api_version()
Return type:[int, int, int]

Returns the version of the API definition (major, minor, revision) implemented by this API bindings. This is neither the release version of this API bindings nor does it tell you anything about the represented Brick or Bricklet.

BrickletRealTimeClock.get_response_expected(function_id)
Parameters:function_id -- int
Return type:bool

Returns the response expected flag for the function specified by the function ID parameter. It is true if the function is expected to send a response, false otherwise.

For getter functions this is enabled by default and cannot be disabled, because those functions will always send a response. For callback configuration functions it is enabled by default too, but can be disabled by set_response_expected(). For setter functions it is disabled by default and can be enabled.

Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

See set_response_expected() for the list of function ID constants available for this function.

BrickletRealTimeClock.set_response_expected(function_id, response_expected)
Parameters:
  • function_id -- int
  • response_expected -- bool
Return type:

None

Changes the response expected flag of the function specified by the function ID parameter. This flag can only be changed for setter (default value: false) and callback configuration functions (default value: true). For getter functions it is always enabled.

Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

The following function ID constants are available for this function:

  • BrickletRealTimeClock.FUNCTION_SET_DATE_TIME = 1
  • BrickletRealTimeClock.FUNCTION_SET_OFFSET = 4
  • BrickletRealTimeClock.FUNCTION_SET_DATE_TIME_CALLBACK_PERIOD = 6
  • BrickletRealTimeClock.FUNCTION_SET_ALARM = 8
BrickletRealTimeClock.set_response_expected_all(response_expected)
Parameters:response_expected -- bool
Return type:None

Changes the response expected flag for all setter and callback configuration functions of this device at once.

BrickletRealTimeClock.get_identity()
Return type:(str, str, chr, [int, int, int], [int, int, int], int)

Returns the UID, the UID where the Bricklet is connected to, the position, the hardware and firmware version as well as the device identifier.

The position can be 'a', 'b', 'c' or 'd'.

The device identifier numbers can be found here. There is also a constant for the device identifier of this Bricklet.

The returned namedtuple has the variables uid, connected_uid, position, hardware_version, firmware_version and device_identifier.

Callback Configuration Functions

BrickletRealTimeClock.register_callback(callback_id, function)
Parameters:
  • callback_id -- int
  • function -- callable
Return type:

None

Registers the given function with the given callback_id.

The available callback IDs with corresponding function signatures are listed below.

BrickletRealTimeClock.set_date_time_callback_period(period)
Parameters:period -- int
Return type:None

Sets the period in ms with which the CALLBACK_DATE_TIME callback is triggered periodically. A value of 0 turns the callback off.

The CALLBACK_DATE_TIME Callback is only triggered if the date or time changed since the last triggering.

The default value is 0.

New in version 2.0.1 (Plugin).

BrickletRealTimeClock.get_date_time_callback_period()
Return type:int

Returns the period as set by set_date_time_callback_period().

New in version 2.0.1 (Plugin).

BrickletRealTimeClock.set_alarm(month, day, hour, minute, second, weekday, interval)
Parameters:
  • month -- int
  • day -- int
  • hour -- int
  • minute -- int
  • second -- int
  • weekday -- int
  • interval -- int
Return type:

None

Configures a repeatable alarm. The CALLBACK_ALARM callback is triggered if the current date and time matches the configured alarm.

Setting a parameter to -1 means that it should be disabled and doesn't take part in the match. Setting all parameters to -1 disables the alarm completely.

For example, to make the alarm trigger every day at 7:30 AM it can be configured as (-1, -1, 7, 30, -1, -1, -1). The hour is set to match 7 and the minute is set to match 30. The alarm is triggered if all enabled parameters match.

The interval has a special role. It allows to make the alarm reconfigure itself. This is useful if you need a repeated alarm that cannot be expressed by matching the current date and time. For example, to make the alarm trigger every 23 seconds it can be configured as (-1, -1, -1, -1, -1, -1, 23). Internally the Bricklet will take the current date and time, add 23 seconds to it and set the result as its alarm. The first alarm will be triggered 23 seconds after the call. Because the interval is not -1, the Bricklet will do the same again internally, take the current date and time, add 23 seconds to it and set that as its alarm. This results in a repeated alarm that triggers every 23 seconds.

The interval can also be used in combination with the other parameters. For example, configuring the alarm as (-1, -1, 7, 30, -1, -1, 300) results in an alarm that triggers every day at 7:30 AM and is then repeated every 5 minutes.

The following constants are available for this function:

  • BrickletRealTimeClock.ALARM_MATCH_DISABLED = -1
  • BrickletRealTimeClock.ALARM_INTERVAL_DISABLED = -1

New in version 2.0.1 (Plugin).

BrickletRealTimeClock.get_alarm()
Return type:(int, int, int, int, int, int, int)

Returns the alarm configuration as set by set_alarm().

The following constants are available for this function:

  • BrickletRealTimeClock.ALARM_MATCH_DISABLED = -1
  • BrickletRealTimeClock.ALARM_INTERVAL_DISABLED = -1

New in version 2.0.1 (Plugin).

The returned namedtuple has the variables month, day, hour, minute, second, weekday and interval.

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the register_callback() function of the device object. The first parameter is the callback ID and the second parameter the callback function:

def my_callback(param):
    print(param)

real_time_clock.register_callback(BrickletRealTimeClock.CALLBACK_EXAMPLE, my_callback)

The available constants with inherent number and type of parameters are described below.

Note

Using callbacks for recurring events is always preferred compared to using getters. It will use less USB bandwidth and the latency will be a lot better, since there is no round trip time.

BrickletRealTimeClock.CALLBACK_DATE_TIME
Parameters:
  • year -- int
  • month -- int
  • day -- int
  • hour -- int
  • minute -- int
  • second -- int
  • centisecond -- int
  • weekday -- int
  • timestamp -- int

This callback is triggered periodically with the period that is set by set_date_time_callback_period(). The parameters are the same as for get_date_time() and get_timestamp() combined.

The CALLBACK_DATE_TIME callback is only triggered if the date or time changed since the last triggering.

The following constants are available for this function:

  • BrickletRealTimeClock.WEEKDAY_MONDAY = 1
  • BrickletRealTimeClock.WEEKDAY_TUESDAY = 2
  • BrickletRealTimeClock.WEEKDAY_WEDNESDAY = 3
  • BrickletRealTimeClock.WEEKDAY_THURSDAY = 4
  • BrickletRealTimeClock.WEEKDAY_FRIDAY = 5
  • BrickletRealTimeClock.WEEKDAY_SATURDAY = 6
  • BrickletRealTimeClock.WEEKDAY_SUNDAY = 7

New in version 2.0.1 (Plugin).

BrickletRealTimeClock.CALLBACK_ALARM
Parameters:
  • year -- int
  • month -- int
  • day -- int
  • hour -- int
  • minute -- int
  • second -- int
  • centisecond -- int
  • weekday -- int
  • timestamp -- int

This callback is triggered every time the current date and time matches the configured alarm (see set_alarm()). The parameters are the same as for get_date_time() and get_timestamp() combined.

The following constants are available for this function:

  • BrickletRealTimeClock.WEEKDAY_MONDAY = 1
  • BrickletRealTimeClock.WEEKDAY_TUESDAY = 2
  • BrickletRealTimeClock.WEEKDAY_WEDNESDAY = 3
  • BrickletRealTimeClock.WEEKDAY_THURSDAY = 4
  • BrickletRealTimeClock.WEEKDAY_FRIDAY = 5
  • BrickletRealTimeClock.WEEKDAY_SATURDAY = 6
  • BrickletRealTimeClock.WEEKDAY_SUNDAY = 7

New in version 2.0.1 (Plugin).

Constants

BrickletRealTimeClock.DEVICE_IDENTIFIER

This constant is used to identify a Real-Time Clock Bricklet.

The get_identity() function and the CALLBACK_ENUMERATE callback of the IP Connection have a device_identifier parameter to specify the Brick's or Bricklet's type.

BrickletRealTimeClock.DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Real-Time Clock Bricklet.