Go - Hall Effect Bricklet

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

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

func main() {
    ipcon := ipconnection.New()
    defer ipcon.Close()
    he, _ := hall_effect_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 edge count without reset.
    count, _ := he.GetEdgeCount(false)
    fmt.Printf("Count: \n", count)

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

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

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

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

    he.RegisterEdgeCountCallback(func(count uint32, value bool) {
        fmt.Printf("Count: %d\n", count)
    })

    // Set period for edge count receiver to 0.05s (50ms).
    // Note: The edge count callback is only called every 0.05 seconds
    //       if the edge count has changed since the last call!
    he.SetEdgeCountCallbackPeriod(50)

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

API

The Hall Effect Bricklet's API is defined in the package github.com/Tinkerforge/go-api-bindings/hall_effect_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 NewHallEffectBricklet(uid string, ipcon *IPConnection)(device HallEffectBricklet, err error)

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

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

func (*HallEffectBricklet)GetValue()(value bool, err error)

Returns true if a magnetic field of 35 Gauss (3.5mT) or greater is detected.

func (*HallEffectBricklet)GetEdgeCount(resetCounter bool)(count uint32, err error)

Returns the current value of the edge counter. You can configure edge type (rising, falling, both) that is counted with (*HallEffectBricklet) SetEdgeCountConfig.

If you set the reset counter to true, the count is set back to 0 directly after it is read.

Advanced Functions

func (*HallEffectBricklet)SetEdgeCountConfig(edgeType EdgeType, debounce uint8)(err error)

The edge type parameter configures if rising edges, falling edges or both are counted. Possible edge types are:

  • 0 = rising (default)
  • 1 = falling
  • 2 = both

A magnetic field of 35 Gauss (3.5mT) or greater causes a falling edge and a magnetic field of 25 Gauss (2.5mT) or smaller causes a rising edge.

If a magnet comes near the Bricklet the signal goes low (falling edge), if a magnet is removed from the vicinity the signal goes high (rising edge).

The debounce time is given in ms.

Configuring an edge counter resets its value to 0.

If you don't know what any of this means, just leave it at default. The default configuration is very likely OK for you.

Default values: 0 (edge type) and 100ms (debounce time)

The following constants are available for this function:

  • EdgeTypeRising = 0
  • EdgeTypeFalling = 1
  • EdgeTypeBoth = 2
func (*HallEffectBricklet)GetEdgeCountConfig()(edgeType EdgeType, debounce uint8, err error)

Returns the edge type and debounce time as set by (*HallEffectBricklet) SetEdgeCountConfig.

The following constants are available for this function:

  • EdgeTypeRising = 0
  • EdgeTypeFalling = 1
  • EdgeTypeBoth = 2
func (*HallEffectBricklet)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 (*HallEffectBricklet)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 (*HallEffectBricklet) 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 (*HallEffectBricklet) SetResponseExpected for the list of function ID constants available for this function.

func (*HallEffectBricklet)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:

  • FunctionSetEdgeCountConfig = 3
  • FunctionSetEdgeInterrupt = 5
  • FunctionSetEdgeCountCallbackPeriod = 7
func (*HallEffectBricklet)SetResponseExpectedAll(responseExpected bool)(err error)

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

func (*HallEffectBricklet)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 (*HallEffectBricklet)SetEdgeInterrupt(edges uint32)(err error)

Sets the number of edges until an interrupt is invoked.

If edges is set to n, an interrupt is invoked for every n-th detected edge.

If edges is set to 0, the interrupt is disabled.

Default value is 0.

func (*HallEffectBricklet)GetEdgeInterrupt()(edges uint32, err error)

Returns the edges as set by (*HallEffectBricklet) SetEdgeInterrupt.

func (*HallEffectBricklet)SetEdgeCountCallbackPeriod(period uint32)(err error)

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

The (*HallEffectBricklet) RegisterEdgeCountCallback callback is only triggered if the edge count has changed since the last triggering.

The default value is 0.

func (*HallEffectBricklet)GetEdgeCountCallbackPeriod()(period uint32, err error)

Returns the period as set by (*HallEffectBricklet) SetEdgeCountCallbackPeriod.

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 (*HallEffectBricklet)RegisterEdgeCountCallback(func(count uint32, value bool))(callbackID uint64)

A callback can be registered for this event with the RegisterEdgeCountCallback() function. This function returns the ID of the registered callback. An added callback can be removed with the DeregisterEdgeCountCallback(callbackID uint64) function.

This callback is triggered periodically with the period that is set by (*HallEffectBricklet) SetEdgeCountCallbackPeriod. The callback parameters are the current count and the current value (see (*HallEffectBricklet) GetValue and (*HallEffectBricklet) GetEdgeCount).

The (*HallEffectBricklet) RegisterEdgeCountCallback callback is only triggered if the count or value changed since the last triggering.

Constants

hall_effect_bricklet.DeviceIdentifier

This constant is used to identify a Hall Effect Bricklet.

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

hall_effect_bricklet.DeviceDisplayName

This constant represents the human readable name of a Hall Effect Bricklet.