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# Ruby - Distance US Bricklet

This is the description of the Ruby API bindings for the Distance US Bricklet. General information and technical specifications for the Distance US Bricklet are summarized in its hardware description.

An installation guide for the Ruby API bindings is part of their general description.

## Examples

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

### Simple

Download (example_simple.rb)

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    #!/usr/bin/env ruby
    # -*- ruby encoding: utf-8 -*-

    require 'tinkerforge/ip_connection'
    require 'tinkerforge/bricklet_distance_us'

    include Tinkerforge

    HOST = 'localhost'
    PORT = 4223
    UID = 'XYZ' # Change to your UID

    ipcon = IPConnection.new # Create IP connection
    dir = BrickletDistanceUS.new UID, ipcon # Create device object

    ipcon.connect HOST, PORT # Connect to brickd
    # Don't use device before ipcon is connected

    # Get current distance
    distance = dir.get_distance_value
    puts "Distance Value: #{distance}"

    puts 'Press key to exit'
    $stdin.gets
    ipcon.disconnect

### Callback

Download (example_callback.rb)

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    #!/usr/bin/env ruby
    # -*- ruby encoding: utf-8 -*-

    require 'tinkerforge/ip_connection'
    require 'tinkerforge/bricklet_distance_us'

    include Tinkerforge

    HOST = 'localhost'
    PORT = 4223
    UID = 'XYZ' # Change to your UID

    ipcon = IPConnection.new # Create IP connection
    dir = BrickletDistanceUS.new UID, ipcon # Create device object

    ipcon.connect HOST, PORT # Connect to brickd
    # Don't use device before ipcon is connected

    # Set Period for distance callback to 0.2s (200ms)
    # Note: The callback is only called every 200ms if the
    #       distance has changed since the last call!
    dir.set_distance_callback_period 200

    # Register distance callback (parameter has unit mm)
    dir.register_callback(BrickletDistanceUS::CALLBACK_DISTANCE) do |distance|
      puts "Distance: #{distance/10.0} cm"
    end

    puts 'Press key to exit'
    $stdin.gets
    ipcon.disconnect

### Threshold

Download (example_threshold.rb)

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    #!/usr/bin/env ruby
    # -*- ruby encoding: utf-8 -*-

    require 'tinkerforge/ip_connection'
    require 'tinkerforge/bricklet_distance_us'

    include Tinkerforge

    HOST = 'localhost'
    PORT = 4223
    UID = 'XYZ' # Change to your UID

    ipcon = IPConnection.new # Create IP connection
    dir = BrickletDistanceUS.new UID, ipcon # Create device object

    ipcon.connect HOST, PORT # Connect to brickd
    # Don't use device before ipcon is connected

    # Get threshold callbacks with a debounce time of 10 seconds (10000ms)
    dir.set_debounce_period 10000

    # Register threshold reached callback for distance value smaller than 200
    dir.register_callback(BrickletDistanceUS::CALLBACK_DISTANCE_REACHED) do |distance|
      puts "Distance Value is smaller than 200: #{distance}"
    end

    # Configure threshold for "smaller than 200"
    dir.set_distance_callback_threshold '<', 200, 0

    puts 'Press key to exit'
    $stdin.gets
    ipcon.disconnect

## API

All methods listed below are thread-safe.

### Basic Functions

`BrickletDistanceUS``::``new`(uid, ipcon) → distance_us

  Parameters:

  - uid -- str
  - ipcon -- IPConnection

  Creates an object with the unique device ID `uid`:

      distance_us = BrickletDistanceUS.new 'YOUR_DEVICE_UID', ipcon

  This object can then be used after the IP Connection is connected (see examples above).

`BrickletDistanceUS``#``get_distance_value` → int

  Returns the current distance value measured by the sensor. The value has a range of 0 to 4095. A small value corresponds to a small distance, a big value corresponds to a big distance. The relation between the measured distance value and the actual distance is affected by the 5V supply voltage (deviations in the supply voltage result in deviations in the distance values) and is non-linear (resolution is bigger at close range).

  If you want to get the distance value periodically, it is recommended to use the callback `::CALLBACK_DISTANCE` and set the period with `#set_distance_callback_period`.

### Advanced Functions

`BrickletDistanceUS``#``set_moving_average`(average) → nil

  Parameters: | average -- int

  Sets the length of a moving averaging for the distance value.

  Setting the length to 0 will turn the averaging completely off. With less averaging, there is more noise on the data.

  The range for the averaging is 0-100.

  The default value is 20.

`BrickletDistanceUS``#``get_moving_average` → int

  Returns the length moving average as set by `#set_moving_average`.

`BrickletDistanceUS``#``get_api_version` → [int, int, int]

  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.

`BrickletDistanceUS``#``get_response_expected`(function_id) → bool

  Parameters: | function_id -- int

  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 `#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.

  See `#set_response_expected` for the list of function ID constants available for this function.

`BrickletDistanceUS``#``set_response_expected`(function_id, response_expected) → nil

  Parameters:

  - function_id -- int
  - response_expected -- 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 and callbacks it is always disabled.

  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:

  - BrickletDistanceUS::FUNCTION_SET_DISTANCE_CALLBACK_PERIOD = 2
  - BrickletDistanceUS::FUNCTION_SET_DISTANCE_CALLBACK_THRESHOLD = 4
  - BrickletDistanceUS::FUNCTION_SET_DEBOUNCE_PERIOD = 6
  - BrickletDistanceUS::FUNCTION_SET_MOVING_AVERAGE = 10

`BrickletDistanceUS``#``set_response_expected_all`(response_expected) → nil

  Parameters: | response_expected -- bool

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

`BrickletDistanceUS``#``get_identity` → [str, str, str, [int, int, int], [int, int, int], int]

  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.

  The returned array has the values `uid`, `connected_uid`, `position`, `hardware_version`, `firmware_version` and `device_identifier`.

### Callback Configuration Functions

`BrickletDistanceUS``#``register_callback`(id) { |param [, ...]| block } → nil

  Parameters: | id -- int

  Registers a callback with ID id to the given block. The available IDs with corresponding function signatures are listed below.

`BrickletDistanceUS``#``set_distance_callback_period`(period) → nil

  Parameters: | period -- int

  Sets the period in ms with which the `::CALLBACK_DISTANCE` callback is triggered periodically. A value of 0 turns the callback off.

  `::CALLBACK_DISTANCE` is only triggered if the distance value has changed since the last triggering.

  The default value is 0.

`BrickletDistanceUS``#``get_distance_callback_period` → int

  Returns the period as set by `#set_distance_callback_period`.

`BrickletDistanceUS``#``set_distance_callback_threshold`(option, min, max) → nil

  Parameters:

  - option -- str
  - min -- int
  - max -- int

  Sets the thresholds for the `::CALLBACK_DISTANCE_REACHED` callback.

  The following options are possible:

  Option | Description
  --- | ---
  'x' | Callback is turned off
  'o' | Callback is triggered when the distance value is outside the min and max values
  'i' | Callback is triggered when the distance value is inside the min and max values
  '<' | Callback is triggered when the distance value is smaller than the min value (max is ignored)
  '>' | Callback is triggered when the distance value is greater than the min value (max is ignored)

  The default value is ('x', 0, 0).

  The following constants are available for this function:

  - BrickletDistanceUS::THRESHOLD_OPTION_OFF = 'x'
  - BrickletDistanceUS::THRESHOLD_OPTION_OUTSIDE = 'o'
  - BrickletDistanceUS::THRESHOLD_OPTION_INSIDE = 'i'
  - BrickletDistanceUS::THRESHOLD_OPTION_SMALLER = '<'
  - BrickletDistanceUS::THRESHOLD_OPTION_GREATER = '>'

`BrickletDistanceUS``#``get_distance_callback_threshold` → [str, int, int]

  Returns the threshold as set by `#set_distance_callback_threshold`.

  The following constants are available for this function:

  - BrickletDistanceUS::THRESHOLD_OPTION_OFF = 'x'
  - BrickletDistanceUS::THRESHOLD_OPTION_OUTSIDE = 'o'
  - BrickletDistanceUS::THRESHOLD_OPTION_INSIDE = 'i'
  - BrickletDistanceUS::THRESHOLD_OPTION_SMALLER = '<'
  - BrickletDistanceUS::THRESHOLD_OPTION_GREATER = '>'

  The returned array has the values `option`, `min` and `max`.

`BrickletDistanceUS``#``set_debounce_period`(debounce) → nil

  Parameters: | debounce -- int

  Sets the period in ms with which the threshold callbacks

  - `::CALLBACK_DISTANCE_REACHED`,

  are triggered, if the thresholds

  - `#set_distance_callback_threshold`,

  keep being reached.

  The default value is 100.

`BrickletDistanceUS``#``get_debounce_period` → int

  Returns the debounce period as set by `#set_debounce_period`.

### Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the `#register_callback` function of the device object. The first parameter is the callback ID and the second parameter is a block:

    distance_us.register_callback BrickletDistanceUS::CALLBACK_EXAMPLE, do |param|
      puts "#{param}"
    end

The available constants with inherent number and type of parameters 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.

`BrickletDistanceUS``::``CALLBACK_DISTANCE`

  Parameters: | distance -- int

  This callback is triggered periodically with the period that is set by `#set_distance_callback_period`. The parameter is the distance value of the sensor.

  `::CALLBACK_DISTANCE` is only triggered if the distance value has changed since the last triggering.

`BrickletDistanceUS``::``CALLBACK_DISTANCE_REACHED`

  Parameters: | distance -- int

  This callback is triggered when the threshold as set by `#set_distance_callback_threshold` is reached. The parameter is the distance value of the sensor.

  If the threshold keeps being reached, the callback is triggered periodically with the period as set by `#set_debounce_period`.

### Constants

`BrickletDistanceUS``::``DEVICE_IDENTIFIER`

  This constant is used to identify a Distance US Bricklet.

  The `#get_identity()` function and the `::CALLBACK_ENUMERATE` callback of the IP Connection have a `device_identifier` parameter to specify the Brick's or Bricklet's type.

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