Modbus - PTC Bricklet

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

API

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

Basic Functions

BrickletPTC.get_temperature
Function ID:

1

Request:

empty payload

Response:
  • temperature -- int32

Returns the temperature of connected sensor. The value has a range of -246 to 849 °C and 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.

BrickletPTC.is_sensor_connected
Function ID:

19

Request:

empty payload

Response:
  • connected -- bool

Returns true if the sensor is connected correctly.

If this function returns false, there is either no Pt100 or Pt1000 sensor connected, the sensor is connected incorrectly or the sensor itself is faulty.

BrickletPTC.set_wire_mode
Function ID:

20

Request:
  • mode -- uint8
Response:

no response

Sets the wire mode of the sensor. Possible values are 2, 3 and 4 which correspond to 2-, 3- and 4-wire sensors. The value has to match the jumper configuration on the Bricklet.

The default value is 2 = 2-wire.

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

  • 2: 2, for mode
  • 3: 3, for mode
  • 4: 4, for mode
BrickletPTC.get_wire_mode
Function ID:

21

Request:

empty payload

Response:
  • mode -- uint8

Returns the wire mode as set by set_wire_mode

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

  • 2: 2, for mode
  • 3: 3, for mode
  • 4: 4, for mode

Advanced Functions

BrickletPTC.get_resistance
Function ID:

2

Request:

empty payload

Response:
  • resistance -- int32

Returns the value as measured by the MAX31865 precision delta-sigma ADC.

The value can be converted with the following formulas:

  • Pt100: resistance = (value * 390) / 32768
  • Pt1000: resistance = (value * 3900) / 32768

If you want to get the resistance periodically, it is recommended to use the CALLBACK_RESISTANCE callback and set the period with set_resistance_callback_period.

BrickletPTC.set_noise_rejection_filter
Function ID:

17

Request:
  • filter -- uint8
Response:

no response

Sets the noise rejection filter to either 50Hz (0) or 60Hz (1). Noise from 50Hz or 60Hz power sources (including harmonics of the AC power's fundamental frequency) is attenuated by 82dB.

Default value is 0 = 50Hz.

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

  • 0: 50hz, for filter
  • 1: 60hz, for filter
BrickletPTC.get_noise_rejection_filter
Function ID:

18

Request:

empty payload

Response:
  • filter -- uint8

Returns the noise rejection filter option as set by set_noise_rejection_filter

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

  • 0: 50hz, for filter
  • 1: 60hz, for filter
BrickletPTC.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

BrickletPTC.set_temperature_callback_period
Function ID:

3

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.

BrickletPTC.get_temperature_callback_period
Function ID:

4

Request:

empty payload

Response:
  • period -- uint32

Returns the period as set by set_temperature_callback_period.

BrickletPTC.set_resistance_callback_period
Function ID:

5

Request:
  • period -- uint32
Response:

no response

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

The CALLBACK_RESISTANCE callback is only triggered if the resistance has changed since the last triggering.

The default value is 0.

BrickletPTC.get_resistance_callback_period
Function ID:

6

Request:

empty payload

Response:
  • period -- uint32

Returns the period as set by set_resistance_callback_period.

BrickletPTC.set_temperature_callback_threshold
Function ID:

7

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
BrickletPTC.get_temperature_callback_threshold
Function ID:

8

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
BrickletPTC.set_resistance_callback_threshold
Function ID:

9

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

no response

Sets the thresholds for the CALLBACK_RESISTANCE_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
BrickletPTC.get_resistance_callback_threshold
Function ID:

10

Request:

empty payload

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

Returns the threshold as set by set_resistance_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
BrickletPTC.set_debounce_period
Function ID:

11

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.

BrickletPTC.get_debounce_period
Function ID:

12

Request:

empty payload

Response:
  • debounce -- uint32

Returns the debounce period as set by set_debounce_period.

BrickletPTC.set_sensor_connected_callback_configuration
Function ID:

22

Request:
  • enabled -- bool
Response:

no response

If you enable this callback, the CALLBACK_SENSOR_CONNECTED callback is triggered every time a Pt sensor is connected/disconnected.

By default this callback is disabled.

New in version 2.0.2 (Plugin).

BrickletPTC.get_sensor_connected_callback_configuration
Function ID:

23

Request:

empty payload

Response:
  • enabled -- bool

Returns the configuration as set by set_sensor_connected_callback_configuration.

New in version 2.0.2 (Plugin).

Callbacks

BrickletPTC.CALLBACK_TEMPERATURE
Function ID:

13

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 connected sensor.

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

BrickletPTC.CALLBACK_TEMPERATURE_REACHED
Function ID:

14

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 connected sensor.

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

BrickletPTC.CALLBACK_RESISTANCE
Function ID:

15

Response:
  • resistance -- int32

This callback is triggered periodically with the period that is set by set_resistance_callback_period. The response value is the resistance of the connected sensor.

The CALLBACK_RESISTANCE callback is only triggered if the resistance has changed since the last triggering.

BrickletPTC.CALLBACK_RESISTANCE_REACHED
Function ID:

16

Response:
  • resistance -- int32

This callback is triggered when the threshold as set by set_resistance_callback_threshold is reached. The response value is the resistance of the connected sensor.

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

BrickletPTC.CALLBACK_SENSOR_CONNECTED
Function ID:

24

Response:
  • connected -- bool

This callback is triggered periodically according to the configuration set by set_sensor_connected_callback_configuration.

The response value is the same as is_sensor_connected.

New in version 2.0.2 (Plugin).