Modbus - Industrial Dual 0-20mA Bricklet

This is the description of the Modbus protocol 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.

API

A general description of the Modbus protocol structure can be found here.

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

BrickletIndustrialDual020mA.get_current
Function ID:

1

Request:
  • sensor -- uint8
Response:
  • current -- int32

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 CALLBACK_CURRENT callback and set the period with set_current_callback_period.

Advanced Functions

BrickletIndustrialDual020mA.set_sample_rate
Function ID:

8

Request:
  • rate -- uint8
Response:

no response

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 meanings are defined for the parameters of this function:

  • 0: 240 sps, for rate
  • 1: 60 sps, for rate
  • 2: 15 sps, for rate
  • 3: 4 sps, for rate
BrickletIndustrialDual020mA.get_sample_rate
Function ID:

9

Request:

empty payload

Response:
  • rate -- uint8

Returns the sample rate as set by set_sample_rate.

The following meanings are defined for the parameters of this function:

  • 0: 240 sps, for rate
  • 1: 60 sps, for rate
  • 2: 15 sps, for rate
  • 3: 4 sps, for rate
BrickletIndustrialDual020mA.get_identity
Function ID:

255

Request:

empty payload

Response:
  • uid -- char[8]
  • connected_uid -- char[8]
  • position -- char
  • hardware_version -- uint8[3]
  • firmware_version -- uint8[3]
  • device_identifier -- uint16

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

Callback Configuration Functions

BrickletIndustrialDual020mA.set_current_callback_period
Function ID:

2

Request:
  • sensor -- uint8
  • period -- uint32
Response:

no response

Sets the period in ms with which the CALLBACK_CURRENT callback is triggered periodically for the given sensor. A value of 0 turns the callback off.

The CALLBACK_CURRENT callback is only triggered if the current has changed since the last triggering.

The default value is 0.

BrickletIndustrialDual020mA.get_current_callback_period
Function ID:

3

Request:
  • sensor -- uint8
Response:
  • period -- uint32

Returns the period as set by set_current_callback_period.

BrickletIndustrialDual020mA.set_current_callback_threshold
Function ID:

4

Request:
  • sensor -- uint8
  • option -- char
  • min -- int32
  • max -- int32
Response:

no response

Sets the thresholds for the CALLBACK_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 meanings are defined for the parameters of this function:

  • x: off, for option
  • o: outside, for option
  • i: inside, for option
  • <: smaller, for option
  • >: greater, for option
BrickletIndustrialDual020mA.get_current_callback_threshold
Function ID:

5

Request:
  • sensor -- uint8
Response:
  • option -- char
  • min -- int32
  • max -- int32

Returns the threshold as set by set_current_callback_threshold.

The following meanings are defined for the parameters of this function:

  • x: off, for option
  • o: outside, for option
  • i: inside, for option
  • <: smaller, for option
  • >: greater, for option
BrickletIndustrialDual020mA.set_debounce_period
Function ID:

6

Request:
  • debounce -- uint32
Response:

no response

Sets the period in ms with which the threshold callback

is triggered, if the threshold

keeps being reached.

The default value is 100.

BrickletIndustrialDual020mA.get_debounce_period
Function ID:

7

Request:

empty payload

Response:
  • debounce -- uint32

Returns the debounce period as set by set_debounce_period.

Callbacks

BrickletIndustrialDual020mA.CALLBACK_CURRENT
Function ID:

10

Response:
  • sensor -- uint8
  • current -- int32

This callback is triggered periodically with the period that is set by set_current_callback_period. The response value is the current of the sensor.

The CALLBACK_CURRENT callback is only triggered if the current has changed since the last triggering.

BrickletIndustrialDual020mA.CALLBACK_CURRENT_REACHED
Function ID:

11

Response:
  • sensor -- uint8
  • current -- int32

This callback is triggered when the threshold as set by set_current_callback_threshold is reached. The response value is the current of the sensor.

If the threshold keeps being reached, the callback is triggered periodically with the period as set by set_debounce_period.