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)

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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 mbar\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)

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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 mbar\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)

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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 mbar\n", float64(airPressure)/1000.0)
        fmt.Println("Enjoy the potentially good weather!")
    })

    // Configure threshold for air pressure "greater than 1025 mbar".
    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 BrickletError, implementing the error interface. The error can have one of the following values:

  • BrickletErrorSuccess = 0
  • BrickletErrorInvalidParameter = 1
  • BrickletErrorFunctionNotSupported = 2
  • BrickletErrorUnknownError = 3

which correspond to the values returned from Bricks and Bricklets.

All functions listed below are thread-safe.

Basic Functions

func NewBarometerBricklet(uid string, ipcon *IPConnection)(device BarometerBricklet, err error)

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

This device object can be used after the IPConnection has been connected (see examples above).

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

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 (*BarometerBricklet) RegisterAirPressureCallback callback and set the period with (*BarometerBricklet) SetAirPressureCallbackPeriod.

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

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 (*BarometerBricklet) SetReferenceAirPressure.

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

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

Sets the reference air pressure in mbar/1000 for the altitude calculation. Valid values are between 10000 and 1200000. 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.

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

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

Advanced Functions

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

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.

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

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).

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

Returns the averaging configuration as set by (*BarometerBricklet) SetAveraging.

New in version 2.0.1 (Plugin).

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

Returns the version of the API definition (major, minor, revision) 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)

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 (*BarometerBricklet) 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 send and errors are silently ignored, because they cannot be detected.

See (*BarometerBricklet) SetResponseExpected for the list of function ID constants available for this function.

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

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 send and errors are silently ignored, because they cannot be detected.

The following function ID constants are available for this function:

  • FunctionSetAirPressureCallbackPeriod = 3
  • FunctionSetAltitudeCallbackPeriod = 5
  • FunctionSetAirPressureCallbackThreshold = 7
  • FunctionSetAltitudeCallbackThreshold = 9
  • FunctionSetDebouncePeriod = 11
  • FunctionSetReferenceAirPressure = 13
  • FunctionSetAveraging = 20
func (*BarometerBricklet)SetResponseExpectedAll(responseExpected bool)(err error)

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

func (*BarometerBricklet)GetIdentity()(uid string, connectedUid string, position rune, hardwareVersion [3]uint8, firmwareVersion [3]uint8, deviceIdentifier uint16, err 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' or 'd'.

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)

Sets the period in ms with which the (*BarometerBricklet) RegisterAirPressureCallback callback is triggered periodically. A value of 0 turns the callback off.

The (*BarometerBricklet) RegisterAirPressureCallback callback is only triggered if the air pressure has changed since the last triggering.

The default value is 0.

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

Returns the period as set by (*BarometerBricklet) SetAirPressureCallbackPeriod.

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

Sets the period in ms with which the (*BarometerBricklet) RegisterAltitudeCallback callback is triggered periodically. A value of 0 turns the callback off.

The (*BarometerBricklet) RegisterAltitudeCallback callback is only triggered if the altitude has changed since the last triggering.

The default value is 0.

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

Returns the period as set by (*BarometerBricklet) SetAltitudeCallbackPeriod.

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

Sets the thresholds for the (*BarometerBricklet) RegisterAirPressureReachedCallback 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 default value is ('x', 0, 0).

The following constants are available for this function:

  • ThresholdOptionOff = 'x'
  • ThresholdOptionOutside = 'o'
  • ThresholdOptionInside = 'i'
  • ThresholdOptionSmaller = '<'
  • ThresholdOptionGreater = '>'
func (*BarometerBricklet)GetAirPressureCallbackThreshold()(option ThresholdOption, min int32, max int32, err error)

Returns the threshold as set by (*BarometerBricklet) SetAirPressureCallbackThreshold.

The following constants are available for this function:

  • ThresholdOptionOff = 'x'
  • ThresholdOptionOutside = 'o'
  • ThresholdOptionInside = 'i'
  • ThresholdOptionSmaller = '<'
  • ThresholdOptionGreater = '>'
func (*BarometerBricklet)SetAltitudeCallbackThreshold(option ThresholdOption, min int32, max int32)(err error)

Sets the thresholds for the (*BarometerBricklet) RegisterAltitudeReachedCallback 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 default value is ('x', 0, 0).

The following constants are available for this function:

  • ThresholdOptionOff = 'x'
  • ThresholdOptionOutside = 'o'
  • ThresholdOptionInside = 'i'
  • ThresholdOptionSmaller = '<'
  • ThresholdOptionGreater = '>'
func (*BarometerBricklet)GetAltitudeCallbackThreshold()(option ThresholdOption, min int32, max int32, err error)

Returns the threshold as set by (*BarometerBricklet) SetAltitudeCallbackThreshold.

The following constants are available for this function:

  • ThresholdOptionOff = 'x'
  • ThresholdOptionOutside = 'o'
  • ThresholdOptionInside = 'i'
  • ThresholdOptionSmaller = '<'
  • ThresholdOptionGreater = '>'
func (*BarometerBricklet)SetDebouncePeriod(debounce uint32)(err error)

Sets the period in ms with which the threshold callbacks

are triggered, if the thresholds

keep being reached.

The default value is 100.

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

Returns the debounce period as set by (*BarometerBricklet) 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.

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)

A callback can be registered for this event with the RegisterAirPressureCallback() function. This function returns the ID of the registered callback. An added callback can be removed with the DeregisterAirPressureCallback(registrationID uint64) function.

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

The (*BarometerBricklet) RegisterAirPressureCallback callback is only triggered if the air pressure has changed since the last triggering.

func (*BarometerBricklet)RegisterAltitudeCallback(func(altitude int32))(registrationID uint64)

A callback can be registered for this event with the RegisterAltitudeCallback() function. This function returns the ID of the registered callback. An added callback can be removed with the DeregisterAltitudeCallback(registrationID uint64) function.

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

The (*BarometerBricklet) RegisterAltitudeCallback callback is only triggered if the altitude has changed since the last triggering.

func (*BarometerBricklet)RegisterAirPressureReachedCallback(func(airPressure int32))(registrationID uint64)

A callback can be registered for this event with the RegisterAirPressureReachedCallback() function. This function returns the ID of the registered callback. An added callback can be removed with the DeregisterAirPressureReachedCallback(registrationID uint64) function.

This callback is triggered when the threshold as set by (*BarometerBricklet) 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 (*BarometerBricklet) SetDebouncePeriod.

func (*BarometerBricklet)RegisterAltitudeReachedCallback(func(altitude int32))(registrationID uint64)

A callback can be registered for this event with the RegisterAltitudeReachedCallback() function. This function returns the ID of the registered callback. An added callback can be removed with the DeregisterAltitudeReachedCallback(registrationID uint64) function.

This callback is triggered when the threshold as set by (*BarometerBricklet) 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 (*BarometerBricklet) SetDebouncePeriod.

Constants

barometer_bricklet.DeviceIdentifier

This constant is used to identify a Barometer Bricklet.

The (*BarometerBricklet) 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.