Specifications / Modbus Protocol / API / Bricklets / Barometer Bricklet

Modbus - Barometer Bricklet¶

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.

API¶

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

Basic Functions¶

BrickletBarometer.get_air_pressure¶

Function ID:	1
Request:	empty payload
Response:	air_pressure – Type: int32, Unit: 1/1000 hPa, Range: [10000 to 1200000]

Returns the air pressure of the air pressure sensor.

If you want to get the air pressure periodically, it is recommended to use the CALLBACK_AIR_PRESSURE callback and set the period with set_air_pressure_callback_period.

BrickletBarometer.get_altitude¶

Function ID:	2
Request:	empty payload
Response:	altitude – Type: int32, Unit: 1 cm, Range: [-2³¹ to 2³¹ - 1]

Returns the relative altitude of the air pressure sensor. The value 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_ALTITUDE callback and set the period with set_altitude_callback_period.

BrickletBarometer.set_reference_air_pressure¶

Function ID:	13
Request:	air_pressure – Type: int32, Unit: 1/1000 hPa, Range: [0, 10000 to 1200000], Default: 1013250
Response:	no response

Sets the reference air pressure 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.

BrickletBarometer.get_reference_air_pressure¶

Function ID:	19
Request:	empty payload
Response:	air_pressure – Type: int32, Unit: 1/1000 hPa, Range: [10000 to 1200000], Default: 1013250

Returns the reference air pressure as set by set_reference_air_pressure.

Advanced Functions¶

BrickletBarometer.get_chip_temperature¶

Function ID:	14
Request:	empty payload
Response:	temperature – Type: int16, Unit: 1/100 °C, Range: [-4000 to 8500]

Returns the temperature of the air pressure sensor.

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.

BrickletBarometer.set_averaging¶

Function ID:	20
Request:	moving_average_pressure – Type: uint8, Range: [0 to 25], Default: 25 average_pressure – Type: uint8, Range: [0 to 10], Default: 10 average_temperature – Type: uint8, Range: [0 to 255], Default: 10
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.

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.

New in version 2.0.1 (Plugin).

BrickletBarometer.get_averaging¶

Function ID:	21
Request:	empty payload
Response:	moving_average_pressure – Type: uint8, Range: [0 to 25], Default: 25 average_pressure – Type: uint8, Range: [0 to 10], Default: 10 average_temperature – Type: uint8, Range: [0 to 255], Default: 10

Returns the averaging configuration as set by set_averaging.

New in version 2.0.1 (Plugin).

BrickletBarometer.set_i2c_mode¶

Function ID:	22
Request:	mode – Type: uint8, Range: See meanings, Default: 0
Response:	no response

Sets the I2C mode. Possible modes are:

0: Fast (400kHz)
1: Slow (100kHz)

If you have problems with obvious outliers in the Barometer Bricklet measurements, they may be caused by EMI issues. In this case it may be helpful to lower the I2C speed.

It is however not recommended to lower the I2C speed in applications where a high throughput needs to be achieved.

New in version 2.0.3 (Plugin).

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

For mode:

0 = Fast
1 = Slow

BrickletBarometer.get_i2c_mode¶

Function ID:	23
Request:	empty payload
Response:	mode – Type: uint8, Range: See meanings, Default: 0

Returns the I2C mode as set by set_i2c_mode.

New in version 2.0.3 (Plugin).

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

For mode:

0 = Fast
1 = Slow

BrickletBarometer.get_identity¶

Function ID:	255
Request:	empty payload
Response:	uid – Type: char[8] connected_uid – Type: char[8] position – Type: char, Range: ['a' to 'h', 'z'] hardware_version – Type: uint8[3] 0: major – Type: uint8, Range: [0 to 255] 1: minor – Type: uint8, Range: [0 to 255] 2: revision – Type: uint8, Range: [0 to 255] firmware_version – Type: uint8[3] 0: major – Type: uint8, Range: [0 to 255] 1: minor – Type: uint8, Range: [0 to 255] 2: revision – Type: uint8, Range: [0 to 255] device_identifier – Type: uint16, Range: [0 to 2¹⁶ - 1]

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', 'd', 'e', 'f', 'g' or 'h' (Bricklet Port). A Bricklet connected to an Isolator Bricklet is always at position 'z'.

The device identifier numbers can be found here.

Callback Configuration Functions¶

BrickletBarometer.set_air_pressure_callback_period¶

Function ID:	3
Request:	period – Type: uint32, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Response:	no response

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

The CALLBACK_AIR_PRESSURE callback is only triggered if the air pressure has changed since the last triggering.

BrickletBarometer.get_air_pressure_callback_period¶

Function ID:	4
Request:	empty payload
Response:	period – Type: uint32, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0

Returns the period as set by set_air_pressure_callback_period.

BrickletBarometer.set_altitude_callback_period¶

Function ID:	5
Request:	period – Type: uint32, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Response:	no response

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

The CALLBACK_ALTITUDE callback is only triggered if the altitude has changed since the last triggering.

BrickletBarometer.get_altitude_callback_period¶

Function ID:	6
Request:	empty payload
Response:	period – Type: uint32, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0

Returns the period as set by set_altitude_callback_period.

BrickletBarometer.set_air_pressure_callback_threshold¶

Function ID:	7
Request:	option – Type: char, Range: See meanings, Default: 'x' min – Type: int32, Unit: 1/1000 hPa, Range: [-2³¹ to 2³¹ - 1], Default: 0 max – Type: int32, Unit: 1/1000 hPa, Range: [-2³¹ to 2³¹ - 1], Default: 0
Response:	no response

Sets the thresholds for the CALLBACK_AIR_PRESSURE_REACHED callback.

The following options are possible:

Option	Description
'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 following meanings are defined for the elements of this function:

For option:

'x' = Off
'o' = Outside
'i' = Inside
'<' = Smaller
'>' = Greater

BrickletBarometer.get_air_pressure_callback_threshold¶

Function ID:	8
Request:	empty payload
Response:	option – Type: char, Range: See meanings, Default: 'x' min – Type: int32, Unit: 1/1000 hPa, Range: [-2³¹ to 2³¹ - 1], Default: 0 max – Type: int32, Unit: 1/1000 hPa, Range: [-2³¹ to 2³¹ - 1], Default: 0

Returns the threshold as set by set_air_pressure_callback_threshold.

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

For option:

'x' = Off
'o' = Outside
'i' = Inside
'<' = Smaller
'>' = Greater

BrickletBarometer.set_altitude_callback_threshold¶

Function ID:	9
Request:	option – Type: char, Range: See meanings, Default: 'x' min – Type: int32, Unit: 1 cm, Range: [-2³¹ to 2³¹ - 1], Default: 0 max – Type: int32, Unit: 1 cm, Range: [-2³¹ to 2³¹ - 1], Default: 0
Response:	no response

Sets the thresholds for the CALLBACK_ALTITUDE_REACHED callback.

The following options are possible:

Option	Description
'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 following meanings are defined for the elements of this function:

For option:

'x' = Off
'o' = Outside
'i' = Inside
'<' = Smaller
'>' = Greater

BrickletBarometer.get_altitude_callback_threshold¶

Function ID:	10
Request:	empty payload
Response:	option – Type: char, Range: See meanings, Default: 'x' min – Type: int32, Unit: 1 cm, Range: [-2³¹ to 2³¹ - 1], Default: 0 max – Type: int32, Unit: 1 cm, Range: [-2³¹ to 2³¹ - 1], Default: 0

Returns the threshold as set by set_altitude_callback_threshold.

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

For option:

'x' = Off
'o' = Outside
'i' = Inside
'<' = Smaller
'>' = Greater

BrickletBarometer.set_debounce_period¶

Function ID:	11
Request:	debounce – Type: uint32, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 100
Response:	no response

Sets the period with which the threshold callbacks

CALLBACK_AIR_PRESSURE_REACHED,
CALLBACK_ALTITUDE_REACHED

are triggered, if the thresholds

set_air_pressure_callback_threshold,
set_altitude_callback_threshold

keep being reached.

BrickletBarometer.get_debounce_period¶

Function ID:	12
Request:	empty payload
Response:	debounce – Type: uint32, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 100

Returns the debounce period as set by set_debounce_period.

Callbacks¶

BrickletBarometer.CALLBACK_AIR_PRESSURE¶

Function ID:	15
Response:	air_pressure – Type: int32, Unit: 1/1000 hPa, Range: [10000 to 1200000]

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.

The CALLBACK_AIR_PRESSURE callback is only triggered if the air pressure has changed since the last triggering.

BrickletBarometer.CALLBACK_ALTITUDE¶

Function ID:	16
Response:	altitude – Type: int32, Unit: 1 cm, Range: [-2³¹ to 2³¹ - 1]

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.

The CALLBACK_ALTITUDE callback is only triggered if the altitude has changed since the last triggering.

BrickletBarometer.CALLBACK_AIR_PRESSURE_REACHED¶

Function ID:	17
Response:	air_pressure – Type: int32, Unit: 1/1000 hPa, Range: [10000 to 1200000]

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.

BrickletBarometer.CALLBACK_ALTITUDE_REACHED¶

Function ID:	18
Response:	altitude – Type: int32, Unit: 1 cm, Range: [-2³¹ to 2³¹ - 1]

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.