Go - GPS Bricklet

This is the description of the Go API bindings for the GPS Bricklet. General information and technical specifications for the GPS 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/gps_bricklet"
    "github.com/Tinkerforge/go-api-bindings/ipconnection"
)

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

func main() {
    ipcon := ipconnection.New()
    defer ipcon.Close()
    gps, _ := gps_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 coordinates.
    latitude, ns, longitude, ew, _, _, _, _, _ := gps.GetCoordinates()

    fmt.Printf("Latitude: %f °\n", float64(latitude)/1000000.0)
    fmt.Printf("N/S: \n", ns)
    fmt.Printf("Longitude: %f °\n", float64(longitude)/1000000.0)
    fmt.Printf("E/W: \n", ew)

    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/gps_bricklet"
    "github.com/Tinkerforge/go-api-bindings/ipconnection"
)

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

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

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

    gps.RegisterCoordinatesCallback(func(latitude uint32, ns rune, longitude uint32, ew rune, pdop uint16, hdop uint16, vdop uint16, epe uint16) {
        fmt.Printf("Latitude: %f °\n", float64(latitude)/1000000.0)
        fmt.Printf("N/S: %c\n", ns)
        fmt.Printf("Longitude: %f °\n", float64(longitude)/1000000.0)
        fmt.Printf("E/W: %c\n", ew)
        fmt.Println()
    })

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

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

API

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

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

  • DeviceErrorSuccess = 0
  • DeviceErrorInvalidParameter = 1
  • DeviceErrorFunctionNotSupported = 2
  • DeviceErrorUnknownError = 3

which correspond to the values returned from Bricks and Bricklets.

All functions listed below are thread-safe.

Basic Functions

func gps_bricklet.New(uid string, ipcon *IPConnection) (device GPSBricklet, err error)

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

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

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

func (*GPSBricklet) GetCoordinates() (latitude uint32, ns rune, longitude uint32, ew rune, pdop uint16, hdop uint16, vdop uint16, epe uint16, err error)

Returns the GPS coordinates. Latitude and longitude are given in the DD.dddddd° format, the value 57123468 means 57.123468°. The parameter ns and ew are the cardinal directions for latitude and longitude. Possible values for ns and ew are 'N', 'S', 'E' and 'W' (north, south, east and west).

PDOP, HDOP and VDOP are the dilution of precision (DOP) values. They specify the additional multiplicative effect of GPS satellite geometry on GPS precision. See here for more information. The values are give in hundredths.

EPE is the "Estimated Position Error". The EPE is given in cm. This is not the absolute maximum error, it is the error with a specific confidence. See here for more information.

This data is only valid if there is currently a fix as indicated by GetStatus().

func (*GPSBricklet) GetStatus() (fix Fix, satellitesView uint8, satellitesUsed uint8, err error)

Returns the current fix status, the number of satellites that are in view and the number of satellites that are currently used.

Possible fix status values can be:

Value Description
1 No Fix, GetCoordinates(), GetAltitude() and GetMotion() return invalid data
2 2D Fix, only GetCoordinates() and GetMotion() return valid data
3 3D Fix, GetCoordinates(), GetAltitude() and GetMotion() return valid data

There is also a blue LED on the Bricklet that indicates the fix status.

The following constants are available for this function:

  • gps_bricklet.FixNoFix = 1
  • gps_bricklet.Fix2DFix = 2
  • gps_bricklet.Fix3DFix = 3
func (*GPSBricklet) GetAltitude() (altitude int32, geoidalSeparation int32, err error)

Returns the current altitude and corresponding geoidal separation.

Both values are given in cm.

This data is only valid if there is currently a fix as indicated by GetStatus().

func (*GPSBricklet) GetMotion() (course uint32, speed uint32, err error)

Returns the current course and speed. Course is given in hundredths degree and speed is given in hundredths km/h. A course of 0° means the Bricklet is traveling north bound and 90° means it is traveling east bound.

Please note that this only returns useful values if an actual movement is present.

This data is only valid if there is currently a fix as indicated by GetStatus().

func (*GPSBricklet) GetDateTime() (date uint32, time uint32, err error)

Returns the current date and time. The date is given in the format ddmmyy and the time is given in the format hhmmss.sss. For example, 140713 means 14.07.13 as date and 195923568 means 19:59:23.568 as time.

Advanced Functions

func (*GPSBricklet) Restart(restartType RestartType) (err error)

Restarts the GPS Bricklet, the following restart types are available:

Value Description
0 Hot start (use all available data in the NV store)
1 Warm start (don't use ephemeris at restart)
2 Cold start (don't use time, position, almanacs and ephemeris at restart)
3 Factory reset (clear all system/user configurations at restart)

The following constants are available for this function:

  • gps_bricklet.RestartTypeHotStart = 0
  • gps_bricklet.RestartTypeWarmStart = 1
  • gps_bricklet.RestartTypeColdStart = 2
  • gps_bricklet.RestartTypeFactoryReset = 3
func (*GPSBricklet) 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 (*GPSBricklet) GetResponseExpected(functionId Function) (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 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.

The following constants are available for this function:

  • gps_bricklet.FunctionRestart = 6
  • gps_bricklet.FunctionSetCoordinatesCallbackPeriod = 7
  • gps_bricklet.FunctionSetStatusCallbackPeriod = 9
  • gps_bricklet.FunctionSetAltitudeCallbackPeriod = 11
  • gps_bricklet.FunctionSetMotionCallbackPeriod = 13
  • gps_bricklet.FunctionSetDateTimeCallbackPeriod = 15
func (*GPSBricklet) SetResponseExpected(functionId Function, 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 constants are available for this function:

  • gps_bricklet.FunctionRestart = 6
  • gps_bricklet.FunctionSetCoordinatesCallbackPeriod = 7
  • gps_bricklet.FunctionSetStatusCallbackPeriod = 9
  • gps_bricklet.FunctionSetAltitudeCallbackPeriod = 11
  • gps_bricklet.FunctionSetMotionCallbackPeriod = 13
  • gps_bricklet.FunctionSetDateTimeCallbackPeriod = 15
func (*GPSBricklet) SetResponseExpectedAll(responseExpected bool) (err error)

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

func (*GPSBricklet) 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 (*GPSBricklet) SetCoordinatesCallbackPeriod(period uint32) (err error)

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

The RegisterCoordinatesCallback callback is only triggered if the coordinates changed since the last triggering.

The default value is 0.

func (*GPSBricklet) GetCoordinatesCallbackPeriod() (period uint32, err error)

Returns the period as set by SetCoordinatesCallbackPeriod().

func (*GPSBricklet) SetStatusCallbackPeriod(period uint32) (err error)

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

The RegisterStatusCallback callback is only triggered if the status changed since the last triggering.

The default value is 0.

func (*GPSBricklet) GetStatusCallbackPeriod() (period uint32, err error)

Returns the period as set by SetStatusCallbackPeriod().

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

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

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

The default value is 0.

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

Returns the period as set by SetAltitudeCallbackPeriod().

func (*GPSBricklet) SetMotionCallbackPeriod(period uint32) (err error)

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

The RegisterMotionCallback callback is only triggered if the motion changed since the last triggering.

The default value is 0.

func (*GPSBricklet) GetMotionCallbackPeriod() (period uint32, err error)

Returns the period as set by SetMotionCallbackPeriod().

func (*GPSBricklet) SetDateTimeCallbackPeriod(period uint32) (err error)

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

The RegisterDateTimeCallback callback is only triggered if the date or time changed since the last triggering.

The default value is 0.

func (*GPSBricklet) GetDateTimeCallbackPeriod() (period uint32, err error)

Returns the period as set by SetDateTimeCallbackPeriod().

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 (*GPSBricklet) RegisterCoordinatesCallback(func(latitude uint32, ns rune, longitude uint32, ew rune, pdop uint16, hdop uint16, vdop uint16, epe uint16)) (registrationId uint64)

A callback can be registered for this event with the RegisterCoordinatesCallback() function. This function returns the ID of the registered callback. An added callback can be removed with the DeregisterCoordinatesCallback(registrationId uint64) function.

This callback is triggered periodically with the period that is set by SetCoordinatesCallbackPeriod(). The parameters are the same as for GetCoordinates().

The RegisterCoordinatesCallback callback is only triggered if the coordinates changed since the last triggering and if there is currently a fix as indicated by GetStatus().

func (*GPSBricklet) RegisterStatusCallback(func(fix Fix, satellitesView uint8, satellitesUsed uint8)) (registrationId uint64)

A callback can be registered for this event with the RegisterStatusCallback() function. This function returns the ID of the registered callback. An added callback can be removed with the DeregisterStatusCallback(registrationId uint64) function.

This callback is triggered periodically with the period that is set by SetStatusCallbackPeriod(). The parameters are the same as for GetStatus().

The RegisterStatusCallback callback is only triggered if the status changed since the last triggering.

The following constants are available for this function:

  • gps_bricklet.FixNoFix = 1
  • gps_bricklet.Fix2DFix = 2
  • gps_bricklet.Fix3DFix = 3
func (*GPSBricklet) RegisterAltitudeCallback(func(altitude int32, geoidalSeparation 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 SetAltitudeCallbackPeriod(). The parameters are the same as for GetAltitude().

The RegisterAltitudeCallback callback is only triggered if the altitude changed since the last triggering and if there is currently a fix as indicated by GetStatus().

func (*GPSBricklet) RegisterMotionCallback(func(course uint32, speed uint32)) (registrationId uint64)

A callback can be registered for this event with the RegisterMotionCallback() function. This function returns the ID of the registered callback. An added callback can be removed with the DeregisterMotionCallback(registrationId uint64) function.

This callback is triggered periodically with the period that is set by SetMotionCallbackPeriod(). The parameters are the same as for GetMotion().

The RegisterMotionCallback callback is only triggered if the motion changed since the last triggering and if there is currently a fix as indicated by GetStatus().

func (*GPSBricklet) RegisterDateTimeCallback(func(date uint32, time uint32)) (registrationId uint64)

A callback can be registered for this event with the RegisterDateTimeCallback() function. This function returns the ID of the registered callback. An added callback can be removed with the DeregisterDateTimeCallback(registrationId uint64) function.

This callback is triggered periodically with the period that is set by SetDateTimeCallbackPeriod(). The parameters are the same as for GetDateTime().

The RegisterDateTimeCallback callback is only triggered if the date or time changed since the last triggering.

Constants

gps_bricklet.DeviceIdentifier

This constant is used to identify a GPS 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.

gps_bricklet.DeviceDisplayName

This constant represents the human readable name of a GPS Bricklet.