MQTT - Current25 Bricklet

This is the description of the MQTT API bindings for the Current25 Bricklet. General information and technical specifications for the Current25 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)

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# Change XYZ to the UID of your Current25 Bricklet

setup:
    # Get current current
    subscribe to tinkerforge/response/current25_bricklet/XYZ/get_current
    publish '' to tinkerforge/request/current25_bricklet/XYZ/get_current

Callback

Download (example-callback.txt)

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# Change XYZ to the UID of your Current25 Bricklet

setup:
    # Handle incoming current callbacks
    subscribe to tinkerforge/callback/current25_bricklet/XYZ/current
    publish '{"register": true}' to tinkerforge/register/current25_bricklet/XYZ/current # Register current callback
    
    # Set period for current callback to 1s (1000ms)
    # Note: The current callback is only called every second
    #       if the current has changed since the last call!
    publish '{"period": 1000}' to tinkerforge/request/current25_bricklet/XYZ/set_current_callback_period

Threshold

Download (example-threshold.txt)

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# Change XYZ to the UID of your Current25 Bricklet

setup:
    # Get threshold callbacks with a debounce time of 10 seconds (10000ms)
    publish '{"debounce": 10000}' to tinkerforge/request/current25_bricklet/XYZ/set_debounce_period
    
    # Handle incoming current reached callbacks
    subscribe to tinkerforge/callback/current25_bricklet/XYZ/current_reached
    publish '{"register": true}' to tinkerforge/register/current25_bricklet/XYZ/current_reached # Register current_reached callback
    
    # Configure threshold for current "greater than 5 A"
    publish '{"option": "greater", "min": 5000, "max": 0}' to tinkerforge/request/current25_bricklet/XYZ/set_current_callback_threshold

API

All published payloads to and from the MQTT bindings are in 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/current25_bricklet/<UID>/get_current
Response payload:
  • current -- int

Returns the current of the sensor. The value is in mA and between -25000mA and 25000mA.

If you want to get the current periodically, it is recommended to use the register/current25_bricklet/<UID>/current callback and set the period with request/current25_bricklet/<UID>/set_current_callback_period.

Advanced Functions

request/current25_bricklet/<UID>/calibrate

Calibrates the 0 value of the sensor. You have to call this function when there is no current present.

The zero point of the current sensor is depending on the exact properties of the analog-to-digital converter, the length of the Bricklet cable and the temperature. Thus, if you change the Brick or the environment in which the Bricklet is used, you might have to recalibrate.

The resulting calibration will be saved on the EEPROM of the Current Bricklet.

request/current25_bricklet/<UID>/is_over_current
Response payload:
  • over -- bool

Returns true if more than 25A were measured.

Note

To reset this value you have to power cycle the Bricklet.

request/current25_bricklet/<UID>/get_analog_value
Response payload:
  • value -- int

Returns the value as read by a 12-bit analog-to-digital converter. The value is between 0 and 4095.

Note

The value returned by request/current25_bricklet/<UID>/get_current is averaged over several samples to yield less noise, while request/current25_bricklet/<UID>/get_analog_value gives back raw unfiltered analog values. The only reason to use request/current25_bricklet/<UID>/get_analog_value is, if you need the full resolution of the analog-to-digital converter.

If you want the analog value periodically, it is recommended to use the register/current25_bricklet/<UID>/analog_value callback and set the period with request/current25_bricklet/<UID>/set_analog_value_callback_period.

request/current25_bricklet/<UID>/get_identity
Response payload:
  • uid -- string
  • connected_uid -- string
  • position -- char
  • 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 Current25's name in a human readable form.

Callback Configuration Functions

request/current25_bricklet/<UID>/set_current_callback_period
Request payload:
  • period -- int

Sets the period in ms with which the register/current25_bricklet/<UID>/current callback is triggered periodically. A value of 0 turns the callback off.

The register/current25_bricklet/<UID>/current callback is only triggered if the current has changed since the last triggering.

The default value is 0.

request/current25_bricklet/<UID>/get_current_callback_period
Response payload:
  • period -- int

Returns the period as set by request/current25_bricklet/<UID>/set_current_callback_period.

request/current25_bricklet/<UID>/set_analog_value_callback_period
Request payload:
  • period -- int

Sets the period in ms with which the register/current25_bricklet/<UID>/analog_value callback is triggered periodically. A value of 0 turns the callback off.

The register/current25_bricklet/<UID>/analog_value callback is only triggered if the analog value has changed since the last triggering.

The default value is 0.

request/current25_bricklet/<UID>/get_analog_value_callback_period
Response payload:
  • period -- int

Returns the period as set by request/current25_bricklet/<UID>/set_analog_value_callback_period.

request/current25_bricklet/<UID>/set_current_callback_threshold
Request payload:
  • option -- char (has symbols)
  • min -- int
  • max -- int

Sets the thresholds for the register/current25_bricklet/<UID>/current_reached callback.

The following options are possible:

Option Description
'x' Callback is turned off
'o' Callback is triggered when the current is outside the min and max values
'i' Callback is triggered when the current is inside the min and max values
'<' Callback is triggered when the current is smaller than the min value (max is ignored)
'>' Callback is triggered when the current is greater than the min value (max is ignored)

The default value is ('x', 0, 0).

The following symbols are available for this function:

for option:

  • "Off" = 'x'
  • "Outside" = 'o'
  • "Inside" = 'i'
  • "Smaller" = '<'
  • "Greater" = '>'
request/current25_bricklet/<UID>/get_current_callback_threshold
Response payload:
  • option -- char (has symbols)
  • min -- int
  • max -- int

Returns the threshold as set by request/current25_bricklet/<UID>/set_current_callback_threshold.

The following symbols are available for this function:

for option:

  • "Off" = 'x'
  • "Outside" = 'o'
  • "Inside" = 'i'
  • "Smaller" = '<'
  • "Greater" = '>'
request/current25_bricklet/<UID>/set_analog_value_callback_threshold
Request payload:
  • option -- char (has symbols)
  • min -- int
  • max -- int

Sets the thresholds for the register/current25_bricklet/<UID>/analog_value_reached callback.

The following options are possible:

Option Description
'x' Callback is turned off
'o' Callback is triggered when the analog value is outside the min and max values
'i' Callback is triggered when the analog value is inside the min and max values
'<' Callback is triggered when the analog value is smaller than the min value (max is ignored)
'>' Callback is triggered when the analog value is greater than the min value (max is ignored)

The default value is ('x', 0, 0).

The following symbols are available for this function:

for option:

  • "Off" = 'x'
  • "Outside" = 'o'
  • "Inside" = 'i'
  • "Smaller" = '<'
  • "Greater" = '>'
request/current25_bricklet/<UID>/get_analog_value_callback_threshold
Response payload:
  • option -- char (has symbols)
  • min -- int
  • max -- int

Returns the threshold as set by request/current25_bricklet/<UID>/set_analog_value_callback_threshold.

The following symbols are available for this function:

for option:

  • "Off" = 'x'
  • "Outside" = 'o'
  • "Inside" = 'i'
  • "Smaller" = '<'
  • "Greater" = '>'
request/current25_bricklet/<UID>/set_debounce_period
Request payload:
  • debounce -- int

Sets the period in ms with which the threshold callbacks

are triggered, if the thresholds

keep being reached.

The default value is 100.

request/current25_bricklet/<UID>/get_debounce_period
Response payload:
  • debounce -- int

Returns the debounce period as set by request/current25_bricklet/<UID>/set_debounce_period.

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/current25_bricklet/<UID>/current
Request payload:
  • register -- bool
Response payload:
  • current -- int

A callback can be registered for this event by publishing to the .../register/current25_bricklet/<UID>/current[/<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/current25_bricklet/<UID>/current[/<SUFFIX>] topic for each registered suffix.

This callback is triggered periodically with the period that is set by request/current25_bricklet/<UID>/set_current_callback_period. The callback payload is the current of the sensor.

The register/current25_bricklet/<UID>/current callback is only triggered if the current has changed since the last triggering.

register/current25_bricklet/<UID>/analog_value
Request payload:
  • register -- bool
Response payload:
  • value -- int

A callback can be registered for this event by publishing to the .../register/current25_bricklet/<UID>/analog_value[/<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/current25_bricklet/<UID>/analog_value[/<SUFFIX>] topic for each registered suffix.

This callback is triggered periodically with the period that is set by request/current25_bricklet/<UID>/set_analog_value_callback_period. The callback payload is the analog value of the sensor.

The register/current25_bricklet/<UID>/analog_value callback is only triggered if the current has changed since the last triggering.

register/current25_bricklet/<UID>/current_reached
Request payload:
  • register -- bool
Response payload:
  • current -- int

A callback can be registered for this event by publishing to the .../register/current25_bricklet/<UID>/current_reached[/<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/current25_bricklet/<UID>/current_reached[/<SUFFIX>] topic for each registered suffix.

This callback is triggered when the threshold as set by request/current25_bricklet/<UID>/set_current_callback_threshold is reached. The callback payload is the current of the sensor.

If the threshold keeps being reached, the callback is triggered periodically with the period as set by request/current25_bricklet/<UID>/set_debounce_period.

register/current25_bricklet/<UID>/analog_value_reached
Request payload:
  • register -- bool
Response payload:
  • value -- int

A callback can be registered for this event by publishing to the .../register/current25_bricklet/<UID>/analog_value_reached[/<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/current25_bricklet/<UID>/analog_value_reached[/<SUFFIX>] topic for each registered suffix.

This callback is triggered when the threshold as set by request/current25_bricklet/<UID>/set_analog_value_callback_threshold is reached. The callback payload is the analog value of the sensor.

If the threshold keeps being reached, the callback is triggered periodically with the period as set by request/current25_bricklet/<UID>/set_debounce_period.

register/current25_bricklet/<UID>/over_current
Request payload:
  • register -- bool

A callback can be registered for this event by publishing to the .../register/current25_bricklet/<UID>/over_current[/<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/current25_bricklet/<UID>/over_current[/<SUFFIX>] topic for each registered suffix.

This callback is triggered when an over current is measured (see request/current25_bricklet/<UID>/is_over_current).