Rust - Multi Touch Bricklet

This is the description of the Rust 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 Rust API bindings is part of their general description. Additional documentation can be found on docs.rs.

Examples

The example code below is Public Domain (CC0 1.0).

Simple

Download (example_simple.rs)

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use std::{error::Error, io};

use tinkerforge::{ip_connection::IpConnection, multi_touch_bricklet::*};

const HOST: &str = "127.0.0.1";
const PORT: u16 = 4223;
const UID: &str = "XYZ"; // Change XYZ to the UID of your Multi Touch Bricklet

fn main() -> Result<(), Box<dyn Error>> {
    let ipcon = IpConnection::new(); // Create IP connection
    let mt = MultiTouchBricklet::new(UID, &ipcon); // Create device object

    ipcon.connect((HOST, PORT)).recv()??; // Connect to brickd
                                          // Don't use device before ipcon is connected

    // Get current touch state
    let state = mt.get_touch_state().recv()?;
    let mut string = String::new();

    if (state & (1 << 12)) == (1 << 12) {
        string.push_str("In proximity, ");
    }

    if (state & 0xfff) == 0 {
        string.push_str("No electrodes touched");
    } else {
        string.push_str("Electrodes ");
        for i in 0..12 {
            if (state & (1 << i)) == (1 << i) {
                string.push_str(&(i.to_string() + " "));
            }
        }
        string.push_str("touched");
    }

    println!("Press enter to exit.");
    let mut _input = String::new();
    io::stdin().read_line(&mut _input)?;
    ipcon.disconnect();
    Ok(())
}

Callback

Download (example_callback.rs)

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use std::{error::Error, io, thread};
use tinkerforge::{ip_connection::IpConnection, multi_touch_bricklet::*};

const HOST: &str = "127.0.0.1";
const PORT: u16 = 4223;
const UID: &str = "XYZ"; // Change XYZ to the UID of your Multi Touch Bricklet

fn main() -> Result<(), Box<dyn Error>> {
    let ipcon = IpConnection::new(); // Create IP connection
    let mt = MultiTouchBricklet::new(UID, &ipcon); // Create device object

    ipcon.connect((HOST, PORT)).recv()??; // Connect to brickd
                                          // Don't use device before ipcon is connected

    let touch_state_receiver = mt.get_touch_state_callback_receiver();

    // Spawn thread to handle received events.
    // This thread ends when the `mt` object
    // is dropped, so there is no need for manual cleanup.
    thread::spawn(move || {
        for state_change in touch_state_receiver {
            let mut string = String::new();

            if (state_change & (1 << 12)) == (1 << 12) {
                string.push_str("In proximity, ");
            }

            if (state_change & 0xfff) == 0 {
                string.push_str("No electrodes touched");
            } else {
                string.push_str("Electrodes ");
                for i in 0..12 {
                    if (state_change & (1 << i)) == (1 << i) {
                        string.push_str(&(i.to_string() + " "));
                    }
                }
                string.push_str("touched");
            }
        }
    });

    println!("Press enter to exit.");
    let mut _input = String::new();
    io::stdin().read_line(&mut _input)?;
    ipcon.disconnect();
    Ok(())
}

API

To allow non-blocking usage, nearly every function of the Rust bindings returns a wrapper around a mpsc::Receiver. To block until the function has finished and get your result, call one of the receiver's recv variants. Those return either the result sent by the device, or any error occured.

Functions returning a result directly will block until the device has finished processing the request.

All functions listed below are thread-safe, those which return a receiver are lock-free.

Basic Functions

pub fn MultiTouchBricklet::new(uid: &str, ip_connection: &IpConnection) → MultiTouchBricklet
Parameters:
  • uid – Type: &str
  • ip_connection – Type: &IPConnection
Returns:
  • multi_touch – Type: MultiTouchBricklet

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

let multi_touch = MultiTouchBricklet::new("YOUR_DEVICE_UID", &ip_connection);

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

pub fn MultiTouchBricklet::get_touch_state(&self) → ConvertingReceiver<u16>
Returns:
  • state – Type: u16, Range: [0 to 216 - 1]

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.

pub fn MultiTouchBricklet::recalibrate(&self) → ConvertingReceiver<()>

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

pub fn MultiTouchBricklet::set_electrode_config(&self, enabled_electrodes: u16) → ConvertingReceiver<()>
Parameters:
  • enabled_electrodes – Type: u16, Range: [0 to 216 - 1]

Enables/disables electrodes with a bitfield (see MultiTouchBricklet::get_touch_state).

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::get_touch_state_callback_receiver callback.

Disabling electrodes will also reduce power consumption.

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

pub fn MultiTouchBricklet::get_electrode_config(&self) → ConvertingReceiver<u16>
Returns:
  • enabled_electrodes – Type: u16, Range: [0 to 216 - 1]

Returns the electrode configuration, as set by MultiTouchBricklet::set_electrode_config.

pub fn MultiTouchBricklet::set_electrode_sensitivity(&self, sensitivity: u8) → ConvertingReceiver<()>
Parameters:
  • sensitivity – Type: u8, Range: [0 to 255]

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.

pub fn MultiTouchBricklet::get_electrode_sensitivity(&self) → ConvertingReceiver<u8>
Returns:
  • sensitivity – Type: u8, Range: [0 to 255]

Returns the current sensitivity, as set by MultiTouchBricklet::set_electrode_sensitivity.

Advanced Functions

pub fn MultiTouchBricklet::get_api_version(&self) → [u8; 3]
Returns:
  • api_version – Type: [u8; 3], Range: [0 to 255]

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.

pub fn MultiTouchBricklet::get_response_expected(&mut self, function_id: u8) → bool
Parameters:
  • function_id – Type: u8, Range: See constants
Returns:
  • response_expected – Type: bool

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::set_response_expected. 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 function_id:

  • MULTI_TOUCH_BRICKLET_FUNCTION_RECALIBRATE = 2
  • MULTI_TOUCH_BRICKLET_FUNCTION_SET_ELECTRODE_CONFIG = 3
  • MULTI_TOUCH_BRICKLET_FUNCTION_SET_ELECTRODE_SENSITIVITY = 6
pub fn MultiTouchBricklet::set_response_expected(&mut self, function_id: u8, response_expected: bool) → ()
Parameters:
  • function_id – Type: u8, Range: See constants
  • response_expected – Type: bool

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 function_id:

  • MULTI_TOUCH_BRICKLET_FUNCTION_RECALIBRATE = 2
  • MULTI_TOUCH_BRICKLET_FUNCTION_SET_ELECTRODE_CONFIG = 3
  • MULTI_TOUCH_BRICKLET_FUNCTION_SET_ELECTRODE_SENSITIVITY = 6
pub fn MultiTouchBricklet::set_response_expected_all(&mut self, response_expected: bool) → ()
Parameters:
  • response_expected – Type: bool

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

pub fn MultiTouchBricklet::get_identity(&self) → ConvertingReceiver<Identity>
Return Object:
  • uid – Type: String, Length: up to 8
  • connected_uid – Type: String, Length: up to 8
  • position – Type: char
  • hardware_version – Type: [u8; 3], Range: [0 to 255]
  • firmware_version – Type: [u8; 3], Range: [0 to 255]
  • device_identifier – Type: u16, Range: [0 to 216 - 1]

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.

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the corresponding get_*_callback_receiver function, which returns a receiver for callback events.

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.

pub fn MultiTouchBricklet::get_touch_state_callback_receiver(&self) → ConvertingCallbackReceiver<u16>
Event:
  • state – Type: u16, Range: [0 to 216 - 1]

Receivers created with this function receive Touch State events.

Returns the current touch state, see MultiTouchBricklet::get_touch_state for information about the state.

This callback is triggered every time the touch state changes.

Constants

pub const MultiTouchBricklet::DEVICE_IDENTIFIER

This constant is used to identify a Multi Touch Bricklet.

The MultiTouchBricklet::get_identity function and the IpConnection::get_enumerate_callback_receiver callback of the IP Connection have a device_identifier parameter to specify the Brick's or Bricklet's type.

pub const MultiTouchBricklet::DEVICE_DISPLAY_NAME

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