Software / API Bindings / Go / API Reference and Examples / Bricklets / Barometer Bricklet

Go - Barometer Bricklet¶

This is the description of the Go API bindings for the Barometer Bricklet. General information and technical specifications for the Barometer Bricklet are summarized in its hardware description.

An installation guide for the Go API bindings is part of their general description. Additional documentation can be found on godoc.org.

Examples¶

The example code below is Public Domain (CC0 1.0).

Simple¶

Download (example_simple.go)

package main

import (
    "fmt"
    "github.com/Tinkerforge/go-api-bindings/barometer_bricklet"
    "github.com/Tinkerforge/go-api-bindings/ipconnection"
)

const ADDR string = "localhost:4223"
const UID string = "XYZ" // Change XYZ to the UID of your Barometer Bricklet.

func main() {
    ipcon := ipconnection.New()
    defer ipcon.Close()
    b, _ := barometer_bricklet.New(UID, &ipcon) // Create device object.

    ipcon.Connect(ADDR) // Connect to brickd.
    defer ipcon.Disconnect()
    // Don't use device before ipcon is connected.

    // Get current air pressure.
    airPressure, _ := b.GetAirPressure()
    fmt.Printf("Air Pressure: %f hPa\n", float64(airPressure)/1000.0)

    // Get current altitude.
    altitude, _ := b.GetAltitude()
    fmt.Printf("Altitude: %f m\n", float64(altitude)/100.0)

    fmt.Print("Press enter to exit.")
    fmt.Scanln()
}

Callback¶

Download (example_callback.go)

package main

import (
    "fmt"
    "github.com/Tinkerforge/go-api-bindings/barometer_bricklet"
    "github.com/Tinkerforge/go-api-bindings/ipconnection"
)

const ADDR string = "localhost:4223"
const UID string = "XYZ" // Change XYZ to the UID of your Barometer Bricklet.

func main() {
    ipcon := ipconnection.New()
    defer ipcon.Close()
    b, _ := barometer_bricklet.New(UID, &ipcon) // Create device object.

    ipcon.Connect(ADDR) // Connect to brickd.
    defer ipcon.Disconnect()
    // Don't use device before ipcon is connected.

    b.RegisterAirPressureCallback(func(airPressure int32) {
        fmt.Printf("Air Pressure: %f hPa\n", float64(airPressure)/1000.0)
    })

    // Set period for air pressure receiver to 1s (1000ms).
    // Note: The air pressure callback is only called every second
    //       if the air pressure has changed since the last call!
    b.SetAirPressureCallbackPeriod(1000)

    fmt.Print("Press enter to exit.")
    fmt.Scanln()
}

Threshold¶

Download (example_threshold.go)

package main

import (
    "fmt"
    "github.com/Tinkerforge/go-api-bindings/barometer_bricklet"
    "github.com/Tinkerforge/go-api-bindings/ipconnection"
)

const ADDR string = "localhost:4223"
const UID string = "XYZ" // Change XYZ to the UID of your Barometer Bricklet.

func main() {
    ipcon := ipconnection.New()
    defer ipcon.Close()
    b, _ := barometer_bricklet.New(UID, &ipcon) // Create device object.

    ipcon.Connect(ADDR) // Connect to brickd.
    defer ipcon.Disconnect()
    // Don't use device before ipcon is connected.

    // Get threshold receivers with a debounce time of 10 seconds (10000ms).
    b.SetDebouncePeriod(10000)

    b.RegisterAirPressureReachedCallback(func(airPressure int32) {
        fmt.Printf("Air Pressure: %f hPa\n", float64(airPressure)/1000.0)
        fmt.Println("Enjoy the potentially good weather!")
    })

    // Configure threshold for air pressure "greater than 1025 hPa".
    b.SetAirPressureCallbackThreshold('>', 1025*1000, 0)

    fmt.Print("Press enter to exit.")
    fmt.Scanln()
}

API¶

The Barometer Bricklet API is defined in the package github.com/Tinkerforge/go-api-bindings/barometer_bricklet

Nearly every function of the Go bindings can return an ipconnection.DeviceError, implementing the error interface. The error can have one of the following values:

ipconnection.DeviceErrorSuccess = 0
ipconnection.DeviceErrorInvalidParameter = 1
ipconnection.DeviceErrorFunctionNotSupported = 2
ipconnection.DeviceErrorUnknownError = 3

which correspond to the values returned from Bricks and Bricklets.

All functions listed below are thread-safe.

Basic Functions¶

func barometer_bricklet.New(uid string, ipcon *IPConnection) (device BarometerBricklet, err error)¶

Parameters:	uid – Type: string ipcon – Type: *IPConnection
Returns:	device – Type: BarometerBricklet err – Type: error

Creates a new BarometerBricklet object with the unique device ID uid and adds it to the IPConnection ipcon:

device, err := barometer_bricklet.New("YOUR_DEVICE_UID", &ipcon)

This device object can be used after the IPConnection has been connected.

func (*BarometerBricklet) GetAirPressure() (airPressure int32, err error)¶

Returns:	airPressure – Type: int32, Unit: 1/1000 hPa, Range: [10000 to 1200000] err – Type: error

Returns the air pressure of the air pressure sensor.

If you want to get the air pressure periodically, it is recommended to use the AirPressureCallback callback and set the period with SetAirPressureCallbackPeriod().

func (*BarometerBricklet) GetAltitude() (altitude int32, err error)¶

Returns:	altitude – Type: int32, Unit: 1 cm, Range: [-2³¹ to 2³¹ - 1] err – Type: error

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 SetReferenceAirPressure().

If you want to get the altitude periodically, it is recommended to use the AltitudeCallback callback and set the period with SetAltitudeCallbackPeriod().

func (*BarometerBricklet) SetReferenceAirPressure(airPressure int32) (err error)¶

Parameters:	airPressure – Type: int32, Unit: 1/1000 hPa, Range: [0, 10000 to 1200000], Default: 1013250
Returns:	err – Type: error

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.

func (*BarometerBricklet) GetReferenceAirPressure() (airPressure int32, err error)¶

Returns:	airPressure – Type: int32, Unit: 1/1000 hPa, Range: [10000 to 1200000], Default: 1013250 err – Type: error

Returns the reference air pressure as set by SetReferenceAirPressure().

Advanced Functions¶

func (*BarometerBricklet) GetChipTemperature() (temperature int16, err error)¶

Returns:	temperature – Type: int16, Unit: 1/100 °C, Range: [-4000 to 8500] err – Type: error

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.

func (*BarometerBricklet) SetAveraging(movingAveragePressure uint8, averagePressure uint8, averageTemperature uint8) (err error)¶

Parameters:	movingAveragePressure – Type: uint8, Range: [0 to 25], Default: 25 averagePressure – Type: uint8, Range: [0 to 10], Default: 10 averageTemperature – Type: uint8, Range: [0 to 255], Default: 10
Returns:	err – Type: error

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).

func (*BarometerBricklet) GetAveraging() (movingAveragePressure uint8, averagePressure uint8, averageTemperature uint8, err error)¶

Returns:	movingAveragePressure – Type: uint8, Range: [0 to 25], Default: 25 averagePressure – Type: uint8, Range: [0 to 10], Default: 10 averageTemperature – Type: uint8, Range: [0 to 255], Default: 10 err – Type: error

Returns the averaging configuration as set by SetAveraging().

New in version 2.0.1 (Plugin).

func (*BarometerBricklet) SetI2CMode(mode uint8) (err error)¶

Parameters:	mode – Type: uint8, Range: See constants, Default: 0
Returns:	err – Type: error

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.

The following constants are available for this function:

For mode:

barometer_bricklet.I2CModeFast = 0
barometer_bricklet.I2CModeSlow = 1

New in version 2.0.3 (Plugin).

func (*BarometerBricklet) GetI2CMode() (mode uint8, err error)¶

Returns:	mode – Type: uint8, Range: See constants, Default: 0 err – Type: error

Returns the I2C mode as set by SetI2CMode().

The following constants are available for this function:

For mode:

barometer_bricklet.I2CModeFast = 0
barometer_bricklet.I2CModeSlow = 1

New in version 2.0.3 (Plugin).

func (*BarometerBricklet) GetIdentity() (uid string, connectedUid string, position rune, hardwareVersion [3]uint8, firmwareVersion [3]uint8, deviceIdentifier uint16, err error)¶

Returns:

Returns:	uid – Type: string, Length: up to 8 connectedUid – Type: string, Length: up to 8 position – Type: rune, Range: ['a' to 'h', 'z'] hardwareVersion – Type: [3]uint8 0: major – Type: uint8, Range: [0 to 255] 1: minor – Type: uint8, Range: [0 to 255] 2: revision – Type: uint8, Range: [0 to 255] firmwareVersion – Type: [3]uint8 0: major – Type: uint8, Range: [0 to 255] 1: minor – Type: uint8, Range: [0 to 255] 2: revision – Type: uint8, Range: [0 to 255] deviceIdentifier – Type: uint16, Range: [0 to 2¹⁶ - 1] err – Type: error

uid – Type: string, Length: up to 8
connectedUid – Type: string, Length: up to 8
position – Type: rune, Range: ['a' to 'h', 'z']
hardwareVersion – Type: [3]uint8

0: major – Type: uint8, Range: [0 to 255]
1: minor – Type: uint8, Range: [0 to 255]
2: revision – Type: uint8, Range: [0 to 255]

firmwareVersion – Type: [3]uint8

0: major – Type: uint8, Range: [0 to 255]
1: minor – Type: uint8, Range: [0 to 255]
2: revision – Type: uint8, Range: [0 to 255]

deviceIdentifier – Type: uint16, Range: [0 to 2¹⁶ - 1]
err – Type: error

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. There is also a constant for the device identifier of this Bricklet.

Callback Configuration Functions¶

func (*BarometerBricklet) SetAirPressureCallbackPeriod(period uint32) (err error)¶

Parameters:	period – Type: uint32, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Returns:	err – Type: error

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

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

func (*BarometerBricklet) GetAirPressureCallbackPeriod() (period uint32, err error)¶

Returns:	period – Type: uint32, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0 err – Type: error

Returns the period as set by SetAirPressureCallbackPeriod().

func (*BarometerBricklet) SetAltitudeCallbackPeriod(period uint32) (err error)¶

Parameters:	period – Type: uint32, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Returns:	err – Type: error

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

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

func (*BarometerBricklet) GetAltitudeCallbackPeriod() (period uint32, err error)¶

Returns:	period – Type: uint32, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0 err – Type: error

Returns the period as set by SetAltitudeCallbackPeriod().

func (*BarometerBricklet) SetAirPressureCallbackThreshold(option rune, min int32, max int32) (err error)¶

Parameters:	option – Type: rune, Range: See constants, 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:	err – Type: error

Sets the thresholds for the AirPressureReachedCallback 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 constants are available for this function:

For option:

barometer_bricklet.ThresholdOptionOff = 'x'
barometer_bricklet.ThresholdOptionOutside = 'o'
barometer_bricklet.ThresholdOptionInside = 'i'
barometer_bricklet.ThresholdOptionSmaller = '<'
barometer_bricklet.ThresholdOptionGreater = '>'

func (*BarometerBricklet) GetAirPressureCallbackThreshold() (option rune, min int32, max int32, err error)¶

Returns:	option – Type: rune, Range: See constants, 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 err – Type: error

Returns the threshold as set by SetAirPressureCallbackThreshold().

The following constants are available for this function:

For option:

barometer_bricklet.ThresholdOptionOff = 'x'
barometer_bricklet.ThresholdOptionOutside = 'o'
barometer_bricklet.ThresholdOptionInside = 'i'
barometer_bricklet.ThresholdOptionSmaller = '<'
barometer_bricklet.ThresholdOptionGreater = '>'

func (*BarometerBricklet) SetAltitudeCallbackThreshold(option rune, min int32, max int32) (err error)¶

Parameters:	option – Type: rune, Range: See constants, 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:	err – Type: error

Sets the thresholds for the AltitudeReachedCallback 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 constants are available for this function:

For option:

barometer_bricklet.ThresholdOptionOff = 'x'
barometer_bricklet.ThresholdOptionOutside = 'o'
barometer_bricklet.ThresholdOptionInside = 'i'
barometer_bricklet.ThresholdOptionSmaller = '<'
barometer_bricklet.ThresholdOptionGreater = '>'

func (*BarometerBricklet) GetAltitudeCallbackThreshold() (option rune, min int32, max int32, err error)¶

Returns:	option – Type: rune, Range: See constants, 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 err – Type: error

Returns the threshold as set by SetAltitudeCallbackThreshold().

The following constants are available for this function:

For option:

barometer_bricklet.ThresholdOptionOff = 'x'
barometer_bricklet.ThresholdOptionOutside = 'o'
barometer_bricklet.ThresholdOptionInside = 'i'
barometer_bricklet.ThresholdOptionSmaller = '<'
barometer_bricklet.ThresholdOptionGreater = '>'

func (*BarometerBricklet) SetDebouncePeriod(debounce uint32) (err error)¶

Parameters:	debounce – Type: uint32, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 100
Returns:	err – Type: error

Sets the period with which the threshold callbacks

AirPressureReachedCallback,
AltitudeReachedCallback

are triggered, if the thresholds

SetAirPressureCallbackThreshold(),
SetAltitudeCallbackThreshold()

keep being reached.

func (*BarometerBricklet) GetDebouncePeriod() (debounce uint32, err error)¶

Returns:	debounce – Type: uint32, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 100 err – Type: error

Returns the debounce period as set by SetDebouncePeriod().

Callbacks¶

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the corresponding Register*Callback function, which returns a unique callback ID. This ID can be used to deregister the callback later with the corresponding Deregister*Callback function.

Note

Using callbacks for recurring events is always preferred compared to using getters. It will use less USB bandwidth and the latency will be a lot better, since there is no round trip time.

func (*BarometerBricklet) RegisterAirPressureCallback(func(airPressure int32)) (registrationId uint64)¶

Callback Parameters:	airPressure – Type: int32, Unit: 1/1000 hPa, Range: [10000 to 1200000]
Returns:	registrationId – Type: uint64

This callback is triggered periodically with the period that is set by SetAirPressureCallbackPeriod(). The callback parameter is the air pressure of the air pressure sensor.

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

func (*BarometerBricklet) RegisterAltitudeCallback(func(altitude int32)) (registrationId uint64)¶

Callback Parameters:	altitude – Type: int32, Unit: 1 cm, Range: [-2³¹ to 2³¹ - 1]
Returns:	registrationId – Type: uint64

This callback is triggered periodically with the period that is set by SetAltitudeCallbackPeriod(). The callback parameter is the altitude of the air pressure sensor.

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

func (*BarometerBricklet) RegisterAirPressureReachedCallback(func(airPressure int32)) (registrationId uint64)¶

Callback Parameters:	airPressure – Type: int32, Unit: 1/1000 hPa, Range: [10000 to 1200000]
Returns:	registrationId – Type: uint64

This callback is triggered when the threshold as set by SetAirPressureCallbackThreshold() is reached. The callback parameter 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 SetDebouncePeriod().

func (*BarometerBricklet) RegisterAltitudeReachedCallback(func(altitude int32)) (registrationId uint64)¶

Callback Parameters:	altitude – Type: int32, Unit: 1 cm, Range: [-2³¹ to 2³¹ - 1]
Returns:	registrationId – Type: uint64

This callback is triggered when the threshold as set by SetAltitudeCallbackThreshold() is reached. The callback parameter 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 SetDebouncePeriod().

Virtual Functions¶

Virtual functions don't communicate with the device itself, but operate only on the API bindings device object. They can be called without the corresponding IP Connection object being connected.

func (*BarometerBricklet) GetAPIVersion() (apiVersion [3]uint8, err error)¶

Returns:	apiVersion – Type: [3]uint8 0: major – Type: uint8, Range: [0 to 255] 1: minor – Type: uint8, Range: [0 to 255] 2: revision – Type: uint8, Range: [0 to 255] err – Type: error

Returns the version of the API definition implemented by this API bindings. This is neither the release version of this API bindings nor does it tell you anything about the represented Brick or Bricklet.

func (*BarometerBricklet) GetResponseExpected(functionId uint8) (responseExpected bool, err error)¶

Parameters:	functionId – Type: uint8, Range: See constants
Returns:	responseExpected – Type: bool err – Type: error

Returns the response expected flag for the function specified by the function ID parameter. It is true if the function is expected to send a response, false otherwise.

For getter functions this is enabled by default and cannot be disabled, because those functions will always send a response. For callback configuration functions it is enabled by default too, but can be disabled by SetResponseExpected(). For setter functions it is disabled by default and can be enabled.

Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is sent and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

For functionId:

barometer_bricklet.FunctionSetAirPressureCallbackPeriod = 3
barometer_bricklet.FunctionSetAltitudeCallbackPeriod = 5
barometer_bricklet.FunctionSetAirPressureCallbackThreshold = 7
barometer_bricklet.FunctionSetAltitudeCallbackThreshold = 9
barometer_bricklet.FunctionSetDebouncePeriod = 11
barometer_bricklet.FunctionSetReferenceAirPressure = 13
barometer_bricklet.FunctionSetAveraging = 20
barometer_bricklet.FunctionSetI2CMode = 22

func (*BarometerBricklet) SetResponseExpected(functionId uint8, responseExpected bool) (err error)¶

Parameters:	functionId – Type: uint8, Range: See constants responseExpected – Type: bool
Returns:	err – Type: error

Changes the response expected flag of the function specified by the function ID parameter. This flag can only be changed for setter (default value: false) and callback configuration functions (default value: true). For getter functions it is always enabled.

The following constants are available for this function:

For functionId:

barometer_bricklet.FunctionSetAirPressureCallbackPeriod = 3
barometer_bricklet.FunctionSetAltitudeCallbackPeriod = 5
barometer_bricklet.FunctionSetAirPressureCallbackThreshold = 7
barometer_bricklet.FunctionSetAltitudeCallbackThreshold = 9
barometer_bricklet.FunctionSetDebouncePeriod = 11
barometer_bricklet.FunctionSetReferenceAirPressure = 13
barometer_bricklet.FunctionSetAveraging = 20
barometer_bricklet.FunctionSetI2CMode = 22

func (*BarometerBricklet) SetResponseExpectedAll(responseExpected bool) (err error)¶

Parameters:	responseExpected – Type: bool
Returns:	err – Type: error

Changes the response expected flag for all setter and callback configuration functions of this device at once.

Constants¶

barometer_bricklet.DeviceIdentifier¶

This constant is used to identify a Barometer Bricklet.

The GetIdentity() function and the (*IPConnection) RegisterEnumerateCallback callback of the IPConnection have a deviceIdentifier parameter to specify the Brick's or Bricklet's type.

barometer_bricklet.DeviceDisplayName¶: This constant represents the human readable name of a Barometer Bricklet.