MQTT - Real-Time Clock Bricklet

This is the description of the MQTT 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 MQTT API bindings is part of their general description.

Examples

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

Simple

Download (example-simple.txt)

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
# Change XYZ to the UID of your Real-Time Clock Bricklet

setup:
    # Get current date and time
    subscribe to tinkerforge/response/real_time_clock_bricklet/XYZ/get_date_time
    publish '' to tinkerforge/request/real_time_clock_bricklet/XYZ/get_date_time
    
    # Get current timestamp
    subscribe to tinkerforge/response/real_time_clock_bricklet/XYZ/get_timestamp
    publish '' to tinkerforge/request/real_time_clock_bricklet/XYZ/get_timestamp

Callback

Download (example-callback.txt)

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
# Change XYZ to the UID of your Real-Time Clock Bricklet

setup:
    # Handle incoming date and time callbacks
    subscribe to tinkerforge/callback/real_time_clock_bricklet/XYZ/date_time
    publish '{"register": true}' to tinkerforge/register/real_time_clock_bricklet/XYZ/date_time # Register date_time callback
    
    # 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!
    publish '{"period": 5000}' to tinkerforge/request/real_time_clock_bricklet/XYZ/set_date_time_callback_period

API

All published payload to an from the MQTT bindings is in the JSON format.

If an error occures, the bindings publish a JSON object containing the error message as attribute "_ERROR". It is published on the corresponding response topic: .../response/... for .../request/... and .../callback/... for .../register/....

Basic Functions

request/real_time_clock_bricklet/<UID>/set_date_time
Request payload:
 
  • year -- int
  • month -- int
  • day -- int
  • hour -- int
  • minute -- int
  • second -- int
  • centisecond -- int
  • weekday -- int (has symbols)

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 symbols are available for this function:

for weekday:

  • "Monday" = 1
  • "Tuesday" = 2
  • "Wednesday" = 3
  • "Thursday" = 4
  • "Friday" = 5
  • "Saturday" = 6
  • "Sunday" = 7
request/real_time_clock_bricklet/<UID>/get_date_time
Response payload:
 
  • year -- int
  • month -- int
  • day -- int
  • hour -- int
  • minute -- int
  • second -- int
  • centisecond -- int
  • weekday -- int (has symbols)

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

The following symbols are available for this function:

for weekday:

  • "Monday" = 1
  • "Tuesday" = 2
  • "Wednesday" = 3
  • "Thursday" = 4
  • "Friday" = 5
  • "Saturday" = 6
  • "Sunday" = 7
request/real_time_clock_bricklet/<UID>/get_timestamp
Response payload:
 
  • timestamp -- 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

request/real_time_clock_bricklet/<UID>/set_offset
Request payload:
 
  • offset -- int

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.

request/real_time_clock_bricklet/<UID>/get_offset
Response payload:
 
  • offset -- int

Returns the offset as set by request/real_time_clock_bricklet/<UID>/set_offset.

request/real_time_clock_bricklet/<UID>/get_identity
Response payload:
 
  • uid -- string
  • connected_uid -- string
  • position -- string
  • hardware_version -- [int,int,int]
  • firmware_version -- [int,int,int]
  • device_identifier -- int (has symbols)
  • _display_name -- string

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. If symbolic output is not disabled, the device identifier is mapped to the corresponding name in the format used in topics.

The display name contains the Real-Time Clock's name in a human readable form.

Callback Configuration Functions

request/real_time_clock_bricklet/<UID>/set_date_time_callback_period
Request payload:
 
  • period -- int

Sets the period in ms with which the register/real_time_clock_bricklet/<UID>/date_time callback is triggered periodically. A value of 0 turns the callback off.

The register/real_time_clock_bricklet/<UID>/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).

request/real_time_clock_bricklet/<UID>/get_date_time_callback_period
Response payload:
 
  • period -- int

Returns the period as set by request/real_time_clock_bricklet/<UID>/set_date_time_callback_period.

New in version 2.0.1 (Plugin).

request/real_time_clock_bricklet/<UID>/set_alarm
Request payload:
 
  • month -- int (has symbols)
  • day -- int (has symbols)
  • hour -- int (has symbols)
  • minute -- int (has symbols)
  • second -- int (has symbols)
  • weekday -- int (has symbols)
  • interval -- int (has symbols)

Configures a repeatable alarm. The register/real_time_clock_bricklet/<UID>/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 symbols are available for this function:

for month:

  • "Disabled" = -1

for interval:

  • "Disabled" = -1

New in version 2.0.1 (Plugin).

request/real_time_clock_bricklet/<UID>/get_alarm
Response payload:
 
  • month -- int (has symbols)
  • day -- int (has symbols)
  • hour -- int (has symbols)
  • minute -- int (has symbols)
  • second -- int (has symbols)
  • weekday -- int (has symbols)
  • interval -- int (has symbols)

Returns the alarm configuration as set by request/real_time_clock_bricklet/<UID>/set_alarm.

The following symbols are available for this function:

for month:

  • "Disabled" = -1

for interval:

  • "Disabled" = -1

New in version 2.0.1 (Plugin).

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the corresponding .../register/... topic and an optional suffix. This suffix can be used to deregister the callback later.

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.

register/real_time_clock_bricklet/<UID>/date_time
Request payload:
 
  • register -- bool
Response payload:
 
  • year -- int
  • month -- int
  • day -- int
  • hour -- int
  • minute -- int
  • second -- int
  • centisecond -- int
  • weekday -- int (has symbols)
  • timestamp -- int

A callback can be registered for this event by publishing to the .../register/real_time_clock_bricklet/<UID>/date_time[/<SUFFIX>] topic with the payload "true". An added callback can be removed by publishing to the same topic with the payload "false". To support multiple (de)registrations, e.g. for message filtering, an optional suffix can be used.

If the callback is triggered, a message with it's payload is published under the corresponding .../callback/real_time_clock_bricklet/<UID>/date_time[/<SUFFIX>] topic for each registered suffix.

This callback is triggered periodically with the period that is set by request/real_time_clock_bricklet/<UID>/set_date_time_callback_period. The callback payload members are the same as for request/real_time_clock_bricklet/<UID>/get_date_time and request/real_time_clock_bricklet/<UID>/get_timestamp combined.

The register/real_time_clock_bricklet/<UID>/date_time callback is only triggered if the date or time changed since the last triggering.

The following symbols are available for this function:

for weekday:

  • "Monday" = 1
  • "Tuesday" = 2
  • "Wednesday" = 3
  • "Thursday" = 4
  • "Friday" = 5
  • "Saturday" = 6
  • "Sunday" = 7

New in version 2.0.1 (Plugin).

register/real_time_clock_bricklet/<UID>/alarm
Request payload:
 
  • register -- bool
Response payload:
 
  • year -- int
  • month -- int
  • day -- int
  • hour -- int
  • minute -- int
  • second -- int
  • centisecond -- int
  • weekday -- int (has symbols)
  • timestamp -- int

A callback can be registered for this event by publishing to the .../register/real_time_clock_bricklet/<UID>/alarm[/<SUFFIX>] topic with the payload "true". An added callback can be removed by publishing to the same topic with the payload "false". To support multiple (de)registrations, e.g. for message filtering, an optional suffix can be used.

If the callback is triggered, a message with it's payload is published under the corresponding .../callback/real_time_clock_bricklet/<UID>/alarm[/<SUFFIX>] topic for each registered suffix.

This callback is triggered every time the current date and time matches the configured alarm (see request/real_time_clock_bricklet/<UID>/set_alarm). The callback payload members are the same as for request/real_time_clock_bricklet/<UID>/get_date_time and request/real_time_clock_bricklet/<UID>/get_timestamp combined.

The following symbols are available for this function:

for weekday:

  • "Monday" = 1
  • "Tuesday" = 2
  • "Wednesday" = 3
  • "Thursday" = 4
  • "Friday" = 5
  • "Saturday" = 6
  • "Sunday" = 7

New in version 2.0.1 (Plugin).