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:breadcrumbs: <a href="../../index.html">Home</a> / <a href="../../index.html#software-delphi">Software</a> / Delphi/Lazarus - Gas Detector Bricklet

.. |device_identifier_constant| replace:: There is also a :ref:`constant <gas_detector_bricklet_delphi_constants>` for the device identifier of this Bricklet.

.. _gas_detector_bricklet_delphi:

Delphi/Lazarus - Gas Detector Bricklet
======================================

.. note::
 This Bricklet is currently in the prototype stage and the software/hardware
 as well as the documentation is in an incomplete state.


This is the description of the :ref:`Delphi/Lazarus API bindings <api_bindings_delphi>` for the :ref:`Gas Detector Bricklet <gas_detector_bricklet>`. General information and technical
specifications for the Gas Detector Bricklet are summarized in its :ref:`hardware description
<gas_detector_bricklet_description>`.

An :ref:`installation guide <api_bindings_delphi_install>` for the Delphi/Lazarus API
bindings is part of their general description.

.. _gas_detector_bricklet_delphi_examples:


Examples
--------

The example code below is `Public Domain (CC0 1.0)
<http://creativecommons.org/publicdomain/zero/1.0/>`__.

.. _gas_detector_bricklet_delphi_api:

API
---

Since Delphi does not support multiple return values directly, we use the
``out`` keyword to return multiple values from a function.

All functions and procedures listed below are thread-safe.




Basic Functions
^^^^^^^^^^^^^^^


.. delphi:function:: constructor TBrickletGasDetector.Create(const uid: string; ipcon: TIPConnection)

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

 .. code-block:: delphi

    gasDetector := TBrickletGasDetector.Create('YOUR_DEVICE_UID', ipcon);

 This object can then be used after the IP Connection is connected
 (see examples :ref:`above <gas_detector_bricklet_delphi_examples>`).


.. delphi:function:: function TBrickletGasDetector.GetValue(): word

 Returns a value between 0 and 4095. 
 
 See `here <TODO>`__ for more information about the measurements.
 
 If you want to get the value periodically, it is recommended 
 to use the callback :delphi:func:`OnValue <TBrickletGasDetector.OnValue>` and set the period with 
 :delphi:func:`SetValueCallbackPeriod <TBrickletGasDetector.SetValueCallbackPeriod>`.
 


Advanced Functions
^^^^^^^^^^^^^^^^^^

.. delphi:function:: procedure TBrickletGasDetector.SetMovingAverage(const average: byte)

 Sets the length of a `moving averaging <http://en.wikipedia.org/wiki/Moving_average>`__ 
 for the measured value.
 
 Setting the length to 1 will turn the averaging off. With less
 averaging, there is more noise on the data.
 
 The range for the averaging is 1-100.
 
 The default value is 100.
 
.. delphi:function:: function TBrickletGasDetector.GetMovingAverage(): byte

 Returns the length moving average as set by :delphi:func:`SetMovingAverage <TBrickletGasDetector.SetMovingAverage>`.
 
.. delphi:function:: procedure TBrickletGasDetector.SetDetectorType(const detectorType: byte)

 Sets the detector type.
 
 The following types are currently supported.
 
 * Type 0: MQ2 and MQ5
 * Type 1: MQ3
 
 The detector type is written to the EEPROM of the Bricklet, so it only has
 to be set once.
 
 You can use the Brick Viewer to set the detector type, so you likely
 don't need to use this function in your source code.
 
 The default detector type is 0.
 
 The following constants are available for this function:
 
 * BRICKLET_GAS_DETECTOR_DETECTOR_TYPE_0 = 0
 * BRICKLET_GAS_DETECTOR_DETECTOR_TYPE_1 = 1
 
.. delphi:function:: function TBrickletGasDetector.GetDetectorType(): byte

 Returns the detector type as set by :delphi:func:`SetDetectorType <TBrickletGasDetector.SetDetectorType>`.
 
 The following constants are available for this function:
 
 * BRICKLET_GAS_DETECTOR_DETECTOR_TYPE_0 = 0
 * BRICKLET_GAS_DETECTOR_DETECTOR_TYPE_1 = 1
 
.. delphi:function:: procedure TBrickletGasDetector.HeaterOn()

 Turns the internal heater on.
 
.. delphi:function:: procedure TBrickletGasDetector.HeaterOff()

 Turns the internal heater off.
 
.. delphi:function:: function TBrickletGasDetector.IsHeaterOn(): boolean

 Returns *true* if the heater is on, *false* otherwise.
 
.. delphi:function:: function TBrickletGasDetector.GetAPIVersion(): array [0..2] of byte

 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.
 
.. delphi:function:: function TBrickletGasDetector.GetResponseExpected(const functionId: byte): boolean

 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
 :delphi:func:`SetResponseExpected <TBrickletGasDetector.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 :delphi:func:`SetResponseExpected <TBrickletGasDetector.SetResponseExpected>`
 for the list of function ID constants available for this function.
 
.. delphi:function:: procedure TBrickletGasDetector.SetResponseExpected(const functionId: byte; const responseExpected: boolean)

 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:
 
 * BRICKLET_GAS_DETECTOR_FUNCTION_SET_VALUE_CALLBACK_PERIOD = 2
 * BRICKLET_GAS_DETECTOR_FUNCTION_SET_VALUE_CALLBACK_THRESHOLD = 4
 * BRICKLET_GAS_DETECTOR_FUNCTION_SET_DEBOUNCE_PERIOD = 6
 * BRICKLET_GAS_DETECTOR_FUNCTION_SET_MOVING_AVERAGE = 8
 * BRICKLET_GAS_DETECTOR_FUNCTION_SET_DETECTOR_TYPE = 10
 * BRICKLET_GAS_DETECTOR_FUNCTION_HEATER_ON = 12
 * BRICKLET_GAS_DETECTOR_FUNCTION_HEATER_OFF = 13
 
.. delphi:function:: procedure TBrickletGasDetector.SetResponseExpectedAll(const responseExpected: boolean)

 Changes the response expected flag for all setter and callback configuration
 functions of this device at once.
 
.. delphi:function:: procedure TBrickletGasDetector.GetIdentity(out uid: string; out connectedUid: string; out position: char; out hardwareVersion: array [0..2] of byte; out firmwareVersion: array [0..2] of byte; out deviceIdentifier: word)

 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 :ref:`here <device_identifier>`.
 |device_identifier_constant|
 


Callback Configuration Functions
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.. delphi:function:: procedure TBrickletGasDetector.SetValueCallbackPeriod(const period: longword)

 Sets the period in ms with which the :delphi:func:`OnValue <TBrickletGasDetector.OnValue>` callback is triggered
 periodically. A value of 0 turns the callback off.
 
 :delphi:func:`OnValue <TBrickletGasDetector.OnValue>` is only triggered if the value value has changed since the
 last triggering.
 
 The default value is 0.
 
.. delphi:function:: function TBrickletGasDetector.GetValueCallbackPeriod(): longword

 Returns the period as set by :delphi:func:`SetValueCallbackPeriod <TBrickletGasDetector.SetValueCallbackPeriod>`.
 
.. delphi:function:: procedure TBrickletGasDetector.SetValueCallbackThreshold(const option: char; const min: word; const max: word)

 Sets the thresholds for the :delphi:func:`OnValueReached <TBrickletGasDetector.OnValueReached>` callback. 
 
 The following options are possible:
 
 .. csv-table::
  :header: "Option", "Description"
  :widths: 10, 100
 
  "'x'",    "Callback is turned off"
  "'o'",    "Callback is triggered when the value value is *outside* the min and max values"
  "'i'",    "Callback is triggered when the value value is *inside* the min and max values"
  "'<'",    "Callback is triggered when the value value is smaller than the min value (max is ignored)"
  "'>'",    "Callback is triggered when the value 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:
 
 * BRICKLET_GAS_DETECTOR_THRESHOLD_OPTION_OFF = 'x'
 * BRICKLET_GAS_DETECTOR_THRESHOLD_OPTION_OUTSIDE = 'o'
 * BRICKLET_GAS_DETECTOR_THRESHOLD_OPTION_INSIDE = 'i'
 * BRICKLET_GAS_DETECTOR_THRESHOLD_OPTION_SMALLER = '<'
 * BRICKLET_GAS_DETECTOR_THRESHOLD_OPTION_GREATER = '>'
 
.. delphi:function:: procedure TBrickletGasDetector.GetValueCallbackThreshold(out option: char; out min: word; out max: word)

 Returns the threshold as set by :delphi:func:`SetValueCallbackThreshold <TBrickletGasDetector.SetValueCallbackThreshold>`.
 
 The following constants are available for this function:
 
 * BRICKLET_GAS_DETECTOR_THRESHOLD_OPTION_OFF = 'x'
 * BRICKLET_GAS_DETECTOR_THRESHOLD_OPTION_OUTSIDE = 'o'
 * BRICKLET_GAS_DETECTOR_THRESHOLD_OPTION_INSIDE = 'i'
 * BRICKLET_GAS_DETECTOR_THRESHOLD_OPTION_SMALLER = '<'
 * BRICKLET_GAS_DETECTOR_THRESHOLD_OPTION_GREATER = '>'
 
.. delphi:function:: procedure TBrickletGasDetector.SetDebouncePeriod(const debounce: longword)

 Sets the period in ms with which the threshold callback
 
 * :delphi:func:`OnValueReached <TBrickletGasDetector.OnValueReached>`
 
 is triggered, if the threshold
 
 * :delphi:func:`SetValueCallbackThreshold <TBrickletGasDetector.SetValueCallbackThreshold>`
 
 keeps being reached.
 
 The default value is 100.
 
.. delphi:function:: function TBrickletGasDetector.GetDebouncePeriod(): longword

 Returns the debounce period as set by :delphi:func:`SetDebouncePeriod <TBrickletGasDetector.SetDebouncePeriod>`.
 




.. _gas_detector_bricklet_delphi_callbacks:

Callbacks
^^^^^^^^^

Callbacks can be registered to receive time critical or recurring data from
the device. The registration is done by assigning a procedure to an callback
property of the device object:

 .. code-block:: delphi

  procedure TExample.MyCallback(sender: TBrickletGasDetector; const param: word);
  begin
    WriteLn(param);
  end;

  gasDetector.OnExample := {$ifdef FPC}@{$endif}example.MyCallback;

The available callback property and their 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.

.. delphi:function:: property TBrickletGasDetector.OnValue

 .. code-block:: delphi

  procedure(sender: TBrickletGasDetector; const value: word) of object;


 This callback is triggered periodically with the period that is set by
 :delphi:func:`SetValueCallbackPeriod <TBrickletGasDetector.SetValueCallbackPeriod>`. The parameter is the value value
 of the sensor.
 
 :delphi:func:`OnValue <TBrickletGasDetector.OnValue>` is only triggered if the value has changed since the
 last triggering.
 
.. delphi:function:: property TBrickletGasDetector.OnValueReached

 .. code-block:: delphi

  procedure(sender: TBrickletGasDetector; const value: word) of object;


 This callback is triggered when the threshold as set by
 :delphi:func:`SetValueCallbackThreshold <TBrickletGasDetector.SetValueCallbackThreshold>` is reached.
 The parameter is the value of the detector.
 
 If the threshold keeps being reached, the callback is triggered periodically
 with the period as set by :delphi:func:`SetDebouncePeriod <TBrickletGasDetector.SetDebouncePeriod>`.
 


.. _gas_detector_bricklet_delphi_constants:

Constants
^^^^^^^^^

.. delphi:function:: const BRICKLET_GAS_DETECTOR_DEVICE_IDENTIFIER

 This constant is used to identify a Gas Detector Bricklet.

 The :delphi:func:`GetIdentity <TBrickletGasDetector.GetIdentity>` function and the
 :delphi:func:`OnEnumerate <TIPConnection.OnEnumerate>`
 callback of the IP Connection have a ``deviceIdentifier`` parameter to specify
 the Brick's or Bricklet's type.

