MQTT - Industrial Dual 0-20mA Bricklet

This is the description of the MQTT API bindings for the Industrial Dual 0-20mA Bricklet. General information and technical specifications for the Industrial Dual 0-20mA 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 Industrial Dual 0-20mA Bricklet

setup:
    # Get current current from sensor 1
    subscribe to tinkerforge/response/industrial_dual_0_20ma_bricklet/XYZ/get_current
    publish '{"sensor": 1}' to tinkerforge/request/industrial_dual_0_20ma_bricklet/XYZ/get_current

Callback

Download (example-callback.txt)

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# Change XYZ to the UID of your Industrial Dual 0-20mA Bricklet

setup:
    # Handle incoming current callbacks
    subscribe to tinkerforge/callback/industrial_dual_0_20ma_bricklet/XYZ/current
    publish '{"register": true}' to tinkerforge/register/industrial_dual_0_20ma_bricklet/XYZ/current # Register current callback
    
    # Set period for current (sensor 1) callback to 1s (1000ms)
    # Note: The current (sensor 1) callback is only called every second
    #       if the current (sensor 1) has changed since the last call!
    publish '{"sensor": 1, "period": 1000}' to tinkerforge/request/industrial_dual_0_20ma_bricklet/XYZ/set_current_callback_period

Threshold

Download (example-threshold.txt)

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# Change XYZ to the UID of your Industrial Dual 0-20mA Bricklet

setup:
    # Get threshold callbacks with a debounce time of 10 seconds (10000ms)
    publish '{"debounce": 10000}' to tinkerforge/request/industrial-dual-0-20ma_bricklet/XYZ/set_debounce_period
    
    # Handle incoming current reached callbacks
    subscribe to tinkerforge/callback/industrial_dual_0_20ma_bricklet/XYZ/current_reached
    publish '{"register": true}' to tinkerforge/register/industrial_dual_0_20ma_bricklet/XYZ/current_reached # Register current_reached callback
    
    # Configure threshold for current (sensor 1) "greater than 10 mA"
    publish '{"sensor": 1, "option": "greater", "min": 10000000, "max": 0}' to tinkerforge/request/industrial_dual_0_20ma_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/....

Two sensors can be connected to the Bricklet. Functions that are related directly to a sensor have a sensor parameter to specify one of the two sensors. Valid values for the sensor parameter are 0 and 1.

Basic Functions

request/industrial_dual_0_20ma_bricklet/<UID>/get_current
Request payload:
 
  • sensor -- int
Response payload:
 
  • current -- int

Returns the current of the specified sensor (0 or 1). The value is in nA and between 0nA and 22505322nA (22.5mA).

It is possible to detect if an IEC 60381-1 compatible sensor is connected and if it works probably.

If the returned current is below 4mA, there is likely no sensor connected or the sensor may be defect. If the returned current is over 20mA, there might be a short circuit or the sensor may be defect.

If you want to get the current periodically, it is recommended to use the register/industrial_dual_0_20ma_bricklet/<UID>/current callback and set the period with request/industrial_dual_0_20ma_bricklet/<UID>/set_current_callback_period.

Advanced Functions

request/industrial_dual_0_20ma_bricklet/<UID>/set_sample_rate
Request payload:
 
  • rate -- int (has symbols)

Sets the sample rate to either 240, 60, 15 or 4 samples per second. The resolution for the rates is 12, 14, 16 and 18 bit respectively.

Value Description
0 240 samples per second, 12 bit resolution
1 60 samples per second, 14 bit resolution
2 15 samples per second, 16 bit resolution
3 4 samples per second, 18 bit resolution

The default value is 3 (4 samples per second with 18 bit resolution).

The following symbols are available for this function:

for rate:

  • "240SPS" = 0
  • "60SPS" = 1
  • "15SPS" = 2
  • "4SPS" = 3
request/industrial_dual_0_20ma_bricklet/<UID>/get_sample_rate
Response payload:
 
  • rate -- int (has symbols)

Returns the sample rate as set by request/industrial_dual_0_20ma_bricklet/<UID>/set_sample_rate.

The following symbols are available for this function:

for rate:

  • "240SPS" = 0
  • "60SPS" = 1
  • "15SPS" = 2
  • "4SPS" = 3
request/industrial_dual_0_20ma_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 Industrial Dual 0-20mA's name in a human readable form.

Callback Configuration Functions

request/industrial_dual_0_20ma_bricklet/<UID>/set_current_callback_period
Request payload:
 
  • sensor -- int
  • period -- int

Sets the period in ms with which the register/industrial_dual_0_20ma_bricklet/<UID>/current callback is triggered periodically for the given sensor. A value of 0 turns the callback off.

The register/industrial_dual_0_20ma_bricklet/<UID>/current callback is only triggered if the current has changed since the last triggering.

The default value is 0.

request/industrial_dual_0_20ma_bricklet/<UID>/get_current_callback_period
Request payload:
 
  • sensor -- int
Response payload:
 
  • period -- int

Returns the period as set by request/industrial_dual_0_20ma_bricklet/<UID>/set_current_callback_period.

request/industrial_dual_0_20ma_bricklet/<UID>/set_current_callback_threshold
Request payload:
 
  • sensor -- int
  • option -- string (has symbols)
  • min -- int
  • max -- int

Sets the thresholds for the register/industrial_dual_0_20ma_bricklet/<UID>/current_reached callback for the given sensor.

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/industrial_dual_0_20ma_bricklet/<UID>/get_current_callback_threshold
Request payload:
 
  • sensor -- int
Response payload:
 
  • option -- string (has symbols)
  • min -- int
  • max -- int

Returns the threshold as set by request/industrial_dual_0_20ma_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/industrial_dual_0_20ma_bricklet/<UID>/set_debounce_period
Request payload:
 
  • debounce -- int

Sets the period in ms with which the threshold callback

is triggered, if the threshold

keeps being reached.

The default value is 100.

request/industrial_dual_0_20ma_bricklet/<UID>/get_debounce_period
Response payload:
 
  • debounce -- int

Returns the debounce period as set by request/industrial_dual_0_20ma_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/industrial_dual_0_20ma_bricklet/<UID>/current
Request payload:
 
  • register -- bool
Response payload:
 
  • sensor -- int
  • current -- int

A callback can be registered for this event by publishing to the .../register/industrial_dual_0_20ma_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/industrial_dual_0_20ma_bricklet/<UID>/current[/<SUFFIX>] topic for each registered suffix.

This callback is triggered periodically with the period that is set by request/industrial_dual_0_20ma_bricklet/<UID>/set_current_callback_period. The callback payload is the current of the sensor.

The register/industrial_dual_0_20ma_bricklet/<UID>/current callback is only triggered if the current has changed since the last triggering.

register/industrial_dual_0_20ma_bricklet/<UID>/current_reached
Request payload:
 
  • register -- bool
Response payload:
 
  • sensor -- int
  • current -- int

A callback can be registered for this event by publishing to the .../register/industrial_dual_0_20ma_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/industrial_dual_0_20ma_bricklet/<UID>/current_reached[/<SUFFIX>] topic for each registered suffix.

This callback is triggered when the threshold as set by request/industrial_dual_0_20ma_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/industrial_dual_0_20ma_bricklet/<UID>/set_debounce_period.