Shell - Multi Touch Bricklet

This is the description of the Shell 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 Shell API bindings is part of their general description.

Examples

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

Simple

Download (example-simple.sh)

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#!/bin/sh
# Connects to localhost:4223 by default, use --host and --port to change this

uid=XYZ # Change XYZ to the UID of your Multi Touch Bricklet

# Get current touch state
tinkerforge call multi-touch-bricklet $uid get-touch-state

Callback

Download (example-callback.sh)

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#!/bin/sh
# Connects to localhost:4223 by default, use --host and --port to change this

uid=XYZ # Change XYZ to the UID of your Multi Touch Bricklet

# Handle incoming touch state callbacks
tinkerforge dispatch multi-touch-bricklet $uid touch-state &

echo "Press key to exit"; read dummy

kill -- -$$ # Stop callback dispatch in background

API

Possible exit codes for all tinkerforge commands are:

  • 1: interrupted (ctrl+c)
  • 2: syntax error
  • 21: Python 2.5 or newer is required
  • 22: Python argparse module is missing
  • 23: socket error
  • 24: other exception
  • 25: invalid placeholder in format string
  • 26: authentication error
  • 201: timeout occurred
  • 209: invalid argument value
  • 210: function is not supported
  • 211: unknown error

Command Structure

The common options of the call and dispatch commands are documented here. The specific command structure is shown below.

tinkerforge call multi-touch-bricklet [<option>..] <uid> <function> [<argument>..]
Parameters:
  • <uid> -- string
  • <function> -- string

The call command is used to call a function of the Multi Touch Bricklet. It can take several options:

  • --help shows help for the specific call command and exits
  • --list-functions shows a list of known functions of the Multi Touch Bricklet and exits
tinkerforge dispatch multi-touch-bricklet [<option>..] <uid> <callback>
Parameters:
  • <uid> -- string
  • <callback> -- string

The dispatch command is used to dispatch a callback of the Multi Touch Bricklet. It can take several options:

  • --help shows help for the specific dispatch command and exits
  • --list-callbacks shows a list of known callbacks of the Multi Touch Bricklet and exits
tinkerforge call multi-touch-bricklet <uid> <function> [<option>..] [<argument>..]
Parameters:
  • <uid> -- string
  • <function> -- string

The <function> to be called can take different options depending of its kind. All functions can take the following options:

  • --help shows help for the specific function and exits

Getter functions can take the following options:

  • --execute <command> shell command line to execute for each incoming response (see section about output formatting for details)

Setter functions can take the following options:

  • --expect-response requests response and waits for it

The --expect-response option for setter functions allows to detect timeouts and other error conditions calls of setters as well. The device will then send a response for this purpose. If this option is not given for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

tinkerforge dispatch multi-touch-bricklet <uid> <callback> [<option>..]
Parameters:
  • <uid> -- string
  • <callback> -- string

The <callback> to be dispatched can take several options:

  • --help shows help for the specific callback and exits
  • --execute <command> shell command line to execute for each incoming response (see section about output formatting for details)

Basic Functions

tinkerforge call multi-touch-bricklet <uid> get-touch-state
Output:
  • state -- int

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.

tinkerforge call multi-touch-bricklet <uid> recalibrate
Output:no output

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

tinkerforge call multi-touch-bricklet <uid> set-electrode-config <enabled-electrodes>
Parameters:
  • <enabled-electrodes> -- int
Output:

no output

Enables/disables electrodes with a bitfield (see 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 touch-state callback.

Disabling electrodes will also reduce power consumption.

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

tinkerforge call multi-touch-bricklet <uid> get-electrode-config
Output:
  • enabled-electrodes -- int

Returns the electrode configuration, as set by set-electrode-config.

tinkerforge call multi-touch-bricklet <uid> set-electrode-sensitivity <sensitivity>
Parameters:
  • <sensitivity> -- int
Output:

no output

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 recalibrate to calibrate the electrodes with the newly defined sensitivity.

The valid sensitivity value range is 5-201.

The default sensitivity value is 181.

tinkerforge call multi-touch-bricklet <uid> get-electrode-sensitivity
Output:
  • sensitivity -- int

Returns the current sensitivity, as set by set-electrode-sensitivity.

Advanced Functions

tinkerforge call multi-touch-bricklet <uid> get-identity
Output:
  • uid -- string
  • connected-uid -- string
  • position -- char
  • hardware-version -- int,int,int
  • firmware-version -- int,int,int
  • device-identifier -- int (has symbols)

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

Callbacks

Callbacks can be used to receive time critical or recurring data from the device:

tinkerforge dispatch multi-touch-bricklet <uid> example

The available callbacks are described below.

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.

tinkerforge dispatch multi-touch-bricklet <uid> touch-state
Output:
  • state -- int

Returns the current touch state, see get-touch-state for information about the state.

This callback is triggered every time the touch state changes.