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 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 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 hall_effect_bricklet.New(uid string, ipcon *IPConnection) (device HallEffectBricklet, err error)
Parameters:
  • uid – Type: string
  • ipcon – Type: *IPConnection
Returns:
  • device – Type: HallEffectBricklet
  • err – Type: error

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

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

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

func (*HallEffectBricklet) GetValue() (value bool, err error)
Returns:
  • value – Type: bool
  • err – Type: error

Returns true if a magnetic field of 3.5 millitesla or greater is detected.

func (*HallEffectBricklet) GetEdgeCount(resetCounter bool) (count uint32, err error)
Parameters:
  • resetCounter – Type: bool
Returns:
  • count – Type: uint32, Range: [0 to 232 - 1]
  • err – Type: error

Returns the current value of the edge counter. You can configure edge type (rising, falling, both) that is counted with 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 uint8, debounce uint8) (err error)
Parameters:
  • edgeType – Type: uint8, Range: See constants, Default: 0
  • debounce – Type: uint8, Unit: 1 ms, Range: [0 to 255], Default: 100
Returns:
  • err – Type: error

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

  • 0 = rising
  • 1 = falling
  • 2 = both

A magnetic field of 3.5 millitesla or greater causes a falling edge and a magnetic field of 2.5 millitesla 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).

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.

The following constants are available for this function:

For edgeType:

  • hall_effect_bricklet.EdgeTypeRising = 0
  • hall_effect_bricklet.EdgeTypeFalling = 1
  • hall_effect_bricklet.EdgeTypeBoth = 2
func (*HallEffectBricklet) GetEdgeCountConfig() (edgeType uint8, debounce uint8, err error)
Returns:
  • edgeType – Type: uint8, Range: See constants, Default: 0
  • debounce – Type: uint8, Unit: 1 ms, Range: [0 to 255], Default: 100
  • err – Type: error

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

The following constants are available for this function:

For edgeType:

  • hall_effect_bricklet.EdgeTypeRising = 0
  • hall_effect_bricklet.EdgeTypeFalling = 1
  • hall_effect_bricklet.EdgeTypeBoth = 2
func (*HallEffectBricklet) GetIdentity() (uid string, connectedUid string, position rune, hardwareVersion [3]uint8, firmwareVersion [3]uint8, deviceIdentifier uint16, err error)
Returns:
  • uid – Type: string, Length: up to 8
  • connectedUid – Type: string, Length: up to 8
  • position – Type: rune, Range: ['a' to 'h', 'i', '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). The Raspberry Pi HAT (Zero) Brick is always at position 'i' and the Bricklet connected to an Isolator Bricklet is always as 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 (*HallEffectBricklet) SetEdgeInterrupt(edges uint32) (err error)
Parameters:
  • edges – Type: uint32, Range: [0 to 232 - 1], Default: 0
Returns:
  • err – Type: 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.

func (*HallEffectBricklet) GetEdgeInterrupt() (edges uint32, err error)
Returns:
  • edges – Type: uint32, Range: [0 to 232 - 1], Default: 0
  • err – Type: error

Returns the edges as set by SetEdgeInterrupt().

func (*HallEffectBricklet) SetEdgeCountCallbackPeriod(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 RegisterEdgeCountCallback callback is triggered periodically. A value of 0 turns the callback off.

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

func (*HallEffectBricklet) GetEdgeCountCallbackPeriod() (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 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 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 (*HallEffectBricklet) RegisterEdgeCountCallback(func(count uint32, value bool)) (registrationId uint64)
Callback Parameters:
  • count – Type: uint32, Range: [0 to 232 - 1]
  • value – Type: bool
Returns:
  • registrationId – Type: uint64

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

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

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

The following constants are available for this function:

For functionId:

  • hall_effect_bricklet.FunctionSetEdgeCountConfig = 3
  • hall_effect_bricklet.FunctionSetEdgeInterrupt = 5
  • hall_effect_bricklet.FunctionSetEdgeCountCallbackPeriod = 7
func (*HallEffectBricklet) 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.

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:

For functionId:

  • hall_effect_bricklet.FunctionSetEdgeCountConfig = 3
  • hall_effect_bricklet.FunctionSetEdgeInterrupt = 5
  • hall_effect_bricklet.FunctionSetEdgeCountCallbackPeriod = 7
func (*HallEffectBricklet) 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

hall_effect_bricklet.DeviceIdentifier

This constant is used to identify a Hall Effect 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.

hall_effect_bricklet.DeviceDisplayName

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