Modbus - Thermocouple Bricklet

This is the description of the Modbus protocol for the Thermocouple Bricklet. General information and technical specifications for the Thermocouple Bricklet are summarized in its hardware description.

API

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

Basic Functions

BrickletThermocouple.get_temperature
Function ID:

1

Request:

empty payload

Response:
  • temperature -- int32

Returns the temperature of the thermocouple. The value is given in °C/100, e.g. a value of 4223 means that a temperature of 42.23 °C is measured.

If you want to get the temperature periodically, it is recommended to use the CALLBACK_TEMPERATURE callback and set the period with set_temperature_callback_period.

Advanced Functions

BrickletThermocouple.set_configuration
Function ID:

10

Request:
  • averaging -- uint8
  • thermocouple_type -- uint8
  • filter -- uint8
Response:

no response

You can configure averaging size, thermocouple type and frequency filtering.

Available averaging sizes are 1, 2, 4, 8 and 16 samples.

As thermocouple type you can use B, E, J, K, N, R, S and T. If you have a different thermocouple or a custom thermocouple you can also use G8 and G32. With these types the returned value will not be in °C/100, it will be calculated by the following formulas:

  • G8: value = 8 * 1.6 * 2^17 * Vin
  • G32: value = 32 * 1.6 * 2^17 * Vin

where Vin is the thermocouple input voltage.

The frequency filter can be either configured to 50Hz or to 60Hz. You should configure it according to your utility frequency.

The conversion time depends on the averaging and filter configuration, it can be calculated as follows:

  • 60Hz: time = 82 + (samples - 1) * 16.67
  • 50Hz: time = 98 + (samples - 1) * 20

The default configuration is 16 samples, K type and 50Hz.

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

  • 1: 1, for averaging
  • 2: 2, for averaging
  • 4: 4, for averaging
  • 8: 8, for averaging
  • 16: 16, for averaging
  • 0: b, for thermocouple_type
  • 1: e, for thermocouple_type
  • 2: j, for thermocouple_type
  • 3: k, for thermocouple_type
  • 4: n, for thermocouple_type
  • 5: r, for thermocouple_type
  • 6: s, for thermocouple_type
  • 7: t, for thermocouple_type
  • 8: g8, for thermocouple_type
  • 9: g32, for thermocouple_type
  • 0: 50hz, for filter
  • 1: 60hz, for filter
BrickletThermocouple.get_configuration
Function ID:

11

Request:

empty payload

Response:
  • averaging -- uint8
  • thermocouple_type -- uint8
  • filter -- uint8

Returns the configuration as set by set_configuration.

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

  • 1: 1, for averaging
  • 2: 2, for averaging
  • 4: 4, for averaging
  • 8: 8, for averaging
  • 16: 16, for averaging
  • 0: b, for thermocouple_type
  • 1: e, for thermocouple_type
  • 2: j, for thermocouple_type
  • 3: k, for thermocouple_type
  • 4: n, for thermocouple_type
  • 5: r, for thermocouple_type
  • 6: s, for thermocouple_type
  • 7: t, for thermocouple_type
  • 8: g8, for thermocouple_type
  • 9: g32, for thermocouple_type
  • 0: 50hz, for filter
  • 1: 60hz, for filter
BrickletThermocouple.get_error_state
Function ID:

12

Request:

empty payload

Response:
  • over_under -- bool
  • open_circuit -- bool

Returns the current error state. There are two possible errors:

  • Over/Under Voltage and
  • Open Circuit.

Over/Under Voltage happens for voltages below 0V or above 3.3V. In this case it is very likely that your thermocouple is defective. An Open Circuit error indicates that there is no thermocouple connected.

You can use the CALLBACK_ERROR_STATE callback to automatically get triggered when the error state changes.

BrickletThermocouple.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

BrickletThermocouple.set_temperature_callback_period
Function ID:

2

Request:
  • period -- uint32
Response:

no response

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

The CALLBACK_TEMPERATURE callback is only triggered if the temperature has changed since the last triggering.

The default value is 0.

BrickletThermocouple.get_temperature_callback_period
Function ID:

3

Request:

empty payload

Response:
  • period -- uint32

Returns the period as set by set_temperature_callback_period.

BrickletThermocouple.set_temperature_callback_threshold
Function ID:

4

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

no response

Sets the thresholds for the CALLBACK_TEMPERATURE_REACHED callback.

The following options are possible:

Option Description
'x' Callback is turned off
'o' Callback is triggered when the temperature is outside the min and max values
'i' Callback is triggered when the temperature is inside the min and max values
'<' Callback is triggered when the temperature is smaller than the min value (max is ignored)
'>' Callback is triggered when the temperature 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
BrickletThermocouple.get_temperature_callback_threshold
Function ID:

5

Request:

empty payload

Response:
  • option -- char
  • min -- int32
  • max -- int32

Returns the threshold as set by set_temperature_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
BrickletThermocouple.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.

BrickletThermocouple.get_debounce_period
Function ID:

7

Request:

empty payload

Response:
  • debounce -- uint32

Returns the debounce period as set by set_debounce_period.

Callbacks

BrickletThermocouple.CALLBACK_TEMPERATURE
Function ID:

8

Response:
  • temperature -- int32

This callback is triggered periodically with the period that is set by set_temperature_callback_period. The response value is the temperature of the thermocouple.

The CALLBACK_TEMPERATURE callback is only triggered if the temperature has changed since the last triggering.

BrickletThermocouple.CALLBACK_TEMPERATURE_REACHED
Function ID:

9

Response:
  • temperature -- int32

This callback is triggered when the threshold as set by set_temperature_callback_threshold is reached. The response value is the temperature of the thermocouple.

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

BrickletThermocouple.CALLBACK_ERROR_STATE
Function ID:

13

Response:
  • over_under -- bool
  • open_circuit -- bool

This Callback is triggered every time the error state changes (see get_error_state).