Go - Multi Touch Bricklet

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

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

func main() {
    ipcon := ipconnection.New()
    defer ipcon.Close()
    mt, _ := multi_touch_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 touch state.
    state, _ := mt.GetTouchState()
    var str string

    if (state & (1 << 12)) == (1 << 12) {
        str += "In proximity, "
    }

    if (state & 0xfff) == 0 {
        str += "No electrodes touched"
    } else {
        str += "Electrodes "
        for i := uint(0); i < 12; i++ {
            if (state & (1 << i)) == (1 << i) {
                str += string(i) + " "
            }
        }
        str += "touched"
    }

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

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

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

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

    mt.RegisterTouchStateCallback(func(state uint16) {
        var str string

        if (state & (1 << 12)) == (1 << 12) {
            str += "In proximity, "
        }

        if (state & 0xfff) == 0 {
            str += "No electrodes touched"
        } else {
            str += "Electrodes "
            for i := uint(0); i < 12; i++ {
                if (state & (1 << i)) == (1 << i) {
                    str += string(i) + " "
                }
            }
            str += "touched"
        }
        fmt.Print(str)
    })

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

API

The Multi Touch Bricklet's API is defined in the package github.com/Tinkerforge/go-api-bindings/multi_touch_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 NewMultiTouchBricklet(uid string, ipcon *IPConnection)(device MultiTouchBricklet, err error)

Creates a new MultiTouchBricklet 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 (*MultiTouchBricklet)GetTouchState()(state uint16, err error)

Returns the current touch state. The state is given as a bitfield.

Bits 0 to 11 represent the 12 electrodes and bit 12 represents the proximity.

If an electrode is touched, the corresponding bit is true. If a hand or similar is in proximity to the electrodes, bit 12 is true.

Example: The state 4103 = 0x1007 = 0b1000000000111 means that electrodes 0, 1 and 2 are touched and that something is in the proximity of the electrodes.

The proximity is activated with a distance of 1-2cm. An electrode is already counted as touched if a finger is nearly touching the electrode. This means that you can put a piece of paper or foil or similar on top of a electrode to build a touch panel with a professional look.

func (*MultiTouchBricklet)Recalibrate()(err error)

Recalibrates the electrodes. Call this function whenever you changed or moved you electrodes.

func (*MultiTouchBricklet)SetElectrodeConfig(enabledElectrodes uint16)(err error)

Enables/disables electrodes with a bitfield (see (*MultiTouchBricklet) GetTouchState).

True enables the electrode, false disables the electrode. A disabled electrode will always return false as its state. If you don't need all electrodes you can disable the electrodes that are not needed.

It is recommended that you disable the proximity bit (bit 12) if the proximity feature is not needed. This will reduce the amount of traffic that is produced by the (*MultiTouchBricklet) RegisterTouchStateCallback callback.

Disabling electrodes will also reduce power consumption.

Default: 8191 = 0x1FFF = 0b1111111111111 (all electrodes enabled)

func (*MultiTouchBricklet)GetElectrodeConfig()(enabledElectrodes uint16, err error)

Returns the electrode configuration, as set by (*MultiTouchBricklet) SetElectrodeConfig.

func (*MultiTouchBricklet)SetElectrodeSensitivity(sensitivity uint8)(err error)

Sets the sensitivity of the electrodes. An electrode with a high sensitivity will register a touch earlier then an electrode with a low sensitivity.

If you build a big electrode you might need to decrease the sensitivity, since the area that can be charged will get bigger. If you want to be able to activate an electrode from further away you need to increase the sensitivity.

After a new sensitivity is set, you likely want to call (*MultiTouchBricklet) Recalibrate to calibrate the electrodes with the newly defined sensitivity.

The valid sensitivity value range is 5-201.

The default sensitivity value is 181.

func (*MultiTouchBricklet)GetElectrodeSensitivity()(sensitivity uint8, err error)

Returns the current sensitivity, as set by (*MultiTouchBricklet) SetElectrodeSensitivity.

Advanced Functions

func (*MultiTouchBricklet)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 (*MultiTouchBricklet)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 (*MultiTouchBricklet) 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 (*MultiTouchBricklet) SetResponseExpected for the list of function ID constants available for this function.

func (*MultiTouchBricklet)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:

  • FunctionRecalibrate = 2
  • FunctionSetElectrodeConfig = 3
  • FunctionSetElectrodeSensitivity = 6
func (*MultiTouchBricklet)SetResponseExpectedAll(responseExpected bool)(err error)

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

func (*MultiTouchBricklet)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

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 (*MultiTouchBricklet)RegisterTouchStateCallback(func(state uint16))(callbackID uint64)

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

Returns the current touch state, see (*MultiTouchBricklet) GetTouchState for information about the state.

This callback is triggered every time the touch state changes.

Constants

multi_touch_bricklet.DeviceIdentifier

This constant is used to identify a Multi Touch Bricklet.

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

multi_touch_bricklet.DeviceDisplayName

This constant represents the human readable name of a Multi Touch Bricklet.