This is the description of the Modbus protocol for the Barometer Bricklet. General information and technical specifications for the Barometer 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 air pressure of the air pressure sensor. The value has a range of 10000 to 1200000 and is given in mbar/1000, i.e. a value of 1001092 means that an air pressure of 1001.092 mbar is measured.
If you want to get the air pressure periodically, it is recommended to use the callback CALLBACK_AIR_PRESSURE and set the period with set_air_pressure_callback_period.
Function ID: | 2 |
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Request: | empty payload |
Response: |
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Returns the relative altitude of the air pressure sensor. The value is given in cm and is calculated based on the difference between the current air pressure and the reference air pressure that can be set with set_reference_air_pressure.
If you want to get the altitude periodically, it is recommended to use the callback CALLBACK_ALTITUDE and set the period with set_altitude_callback_period.
Function ID: | 13 |
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Request: |
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Response: | no response |
Sets the reference air pressure in mbar/1000 for the altitude calculation. Setting the reference to the current air pressure results in a calculated altitude of 0cm. Passing 0 is a shortcut for passing the current air pressure as reference.
Well known reference values are the Q codes QNH and QFE used in aviation.
The default value is 1013.25mbar.
Function ID: | 19 |
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Request: | empty payload |
Response: |
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Returns the reference air pressure as set by set_reference_air_pressure.
Function ID: | 14 |
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Request: | empty payload |
Response: |
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Returns the temperature of the air pressure sensor. The value has a range of -4000 to 8500 and is given in °C/100, i.e. a value of 2007 means that a temperature of 20.07 °C is measured.
This temperature is used internally for temperature compensation of the air pressure measurement. It is not as accurate as the temperature measured by the Temperature Bricklet or the Temperature IR Bricklet.
Function ID: | 20 |
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Request: |
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Response: | no response |
Sets the different averaging parameters. It is possible to set the length of a normal averaging for the temperature and pressure, as well as an additional length of a moving average for the pressure. The moving average is calculated from the normal averages. There is no moving average for the temperature.
The maximum length for the pressure average is 10, for the temperature average is 255 and for the moving average is 25.
Setting the all three parameters to 0 will turn the averaging completely off. If the averaging is off, there is lots of noise on the data, but the data is without delay. Thus we recommend to turn the averaging off if the Barometer Bricklet data is to be used for sensor fusion with other sensors.
The default values are 10 for the normal averages and 25 for the moving average.
New in version 2.0.1 (Plugin).
Function ID: | 21 |
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Request: | empty payload |
Response: |
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Returns the averaging configuration as set by set_averaging.
New in version 2.0.1 (Plugin).
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: |
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Response: | no response |
Sets the period in ms with which the CALLBACK_AIR_PRESSURE callback is triggered periodically. A value of 0 turns the callback off.
CALLBACK_AIR_PRESSURE is only triggered if the air pressure 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_air_pressure_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_ALTITUDE callback is triggered periodically. A value of 0 turns the callback off.
CALLBACK_ALTITUDE is only triggered if the altitude 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_altitude_callback_period.
Function ID: | 7 |
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Request: |
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Response: | no response |
Sets the thresholds for the CALLBACK_AIR_PRESSURE_REACHED callback.
The following options are possible:
Option | Description |
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'x' | Callback is turned off |
'o' | Callback is triggered when the air pressure is outside the min and max values |
'i' | Callback is triggered when the air pressure is inside the min and max values |
'<' | Callback is triggered when the air pressure is smaller than the min value (max is ignored) |
'>' | Callback is triggered when the air pressure 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_air_pressure_callback_threshold.
Function ID: | 9 |
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Request: |
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Response: | no response |
Sets the thresholds for the CALLBACK_ALTITUDE_REACHED callback.
The following options are possible:
Option | Description |
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'x' | Callback is turned off |
'o' | Callback is triggered when the altitude is outside the min and max values |
'i' | Callback is triggered when the altitude is inside the min and max values |
'<' | Callback is triggered when the altitude is smaller than the min value (max is ignored) |
'>' | Callback is triggered when the altitude 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_altitude_callback_threshold.
Function ID: | 11 |
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Request: |
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Response: | no response |
Sets the period in ms with which the threshold callbacks
are triggered, if the thresholds
keep 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: | 15 |
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Response: |
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This callback is triggered periodically with the period that is set by set_air_pressure_callback_period. The response value is the air pressure of the air pressure sensor.
CALLBACK_AIR_PRESSURE is only triggered if the air pressure has changed since the last triggering.
Function ID: | 16 |
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Response: |
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This callback is triggered periodically with the period that is set by set_altitude_callback_period. The response value is the altitude of the air pressure sensor.
CALLBACK_ALTITUDE is only triggered if the altitude has changed since the last triggering.
Function ID: | 17 |
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Response: |
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This callback is triggered when the threshold as set by set_air_pressure_callback_threshold is reached. The response value is the air pressure of the air pressure sensor.
If the threshold keeps being reached, the callback is triggered periodically with the period as set by set_debounce_period.
Function ID: | 18 |
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Response: |
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This callback is triggered when the threshold as set by set_altitude_callback_threshold is reached. The response value is the altitude of the air pressure sensor.
If the threshold keeps being reached, the callback is triggered periodically with the period as set by set_debounce_period.