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.
A general description of the Modbus protocol structure can be found here.
Function ID: | 1 |
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Request: | empty payload |
Response: |
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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 CALLBACK_TEMPERATURE and set the period with set_temperature_callback_period.
Function ID: | 19 |
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Request: | empty payload |
Response: |
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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.
Function ID: | 20 |
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Request: |
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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.
Function ID: | 21 |
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Request: | empty payload |
Response: |
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Returns the wire mode as set by set_wire_mode
Function ID: | 2 |
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Request: | empty payload |
Response: |
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Returns the value as measured by the MAX31865 precision delta-sigma ADC.
The value can be converted with the following formulas:
If you want to get the resistance periodically, it is recommended to use the callback CALLBACK_RESISTANCE and set the period with set_resistance_callback_period.
Function ID: | 17 |
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Request: |
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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.
Function ID: | 18 |
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Request: | empty payload |
Response: |
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Returns the noise rejection filter option as set by set_noise_rejection_filter
Function ID: | 255 |
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Request: | empty payload |
Response: |
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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.
Function ID: | 3 |
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Request: |
|
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.
CALLBACK_TEMPERATURE is only triggered if the temperature has changed since the last triggering.
The default value is 0.
Function ID: | 4 |
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Request: | empty payload |
Response: |
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Returns the period as set by set_temperature_callback_period.
Function ID: | 5 |
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Request: |
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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.
CALLBACK_RESISTANCE is only triggered if the resistance has changed since the last triggering.
The default value is 0.
Function ID: | 6 |
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Request: | empty payload |
Response: |
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Returns the period as set by set_resistance_callback_period.
Function ID: | 7 |
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Request: |
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Response: | no response |
Sets the thresholds for the CALLBACK_TEMPERATURE_REACHED callback.
The following options are possible:
Option | Description |
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'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).
Function ID: | 8 |
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Request: | empty payload |
Response: |
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Returns the threshold as set by set_temperature_callback_threshold.
Function ID: | 9 |
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Request: |
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Response: | no response |
Sets the thresholds for the CALLBACK_RESISTANCE_REACHED callback.
The following options are possible:
Option | Description |
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'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).
Function ID: | 10 |
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Request: | empty payload |
Response: |
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Returns the threshold as set by set_resistance_callback_threshold.
Function ID: | 11 |
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Request: |
|
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.
Function ID: | 12 |
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Request: | empty payload |
Response: |
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Returns the debounce period as set by set_debounce_period.
Function ID: | 13 |
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Response: |
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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.
CALLBACK_TEMPERATURE is only triggered if the temperature has changed since the last triggering.
Function ID: | 14 |
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Response: |
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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.
Function ID: | 15 |
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Response: |
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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.
CALLBACK_RESISTANCE is only triggered if the resistance has changed since the last triggering.
Function ID: | 16 |
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Response: |
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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.