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

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

.. _hall_effect_bricklet_delphi:

Delphi/Lazarus - Hall Effect Bricklet
=====================================

This is the description of the :ref:`Delphi/Lazarus API bindings <api_bindings_delphi>` for the :ref:`Hall Effect Bricklet <hall_effect_bricklet>`. General information and technical
specifications for the Hall Effect Bricklet are summarized in its :ref:`hardware description
<hall_effect_bricklet_description>`.

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

.. _hall_effect_bricklet_delphi_examples:


Examples
--------

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

Simple
^^^^^^

`Download (ExampleSimple.pas) <https://github.com/Tinkerforge/hall-effect-bricklet/raw/master/software/examples/delphi/ExampleSimple.pas>`__

.. literalinclude:: HallEffect_Bricklet_Delphi_ExampleSimple.pas
 :language: delphi
 :linenos:
 :tab-width: 4

Callback
^^^^^^^^

`Download (ExampleCallback.pas) <https://github.com/Tinkerforge/hall-effect-bricklet/raw/master/software/examples/delphi/ExampleCallback.pas>`__

.. literalinclude:: HallEffect_Bricklet_Delphi_ExampleCallback.pas
 :language: delphi
 :linenos:
 :tab-width: 4

.. _hall_effect_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 TBrickletHallEffect.Create(const uid: string; ipcon: TIPConnection)

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

 .. code-block:: delphi

    hallEffect := TBrickletHallEffect.Create('YOUR_DEVICE_UID', ipcon);

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


.. delphi:function:: function TBrickletHallEffect.GetValue(): boolean

 Returns *true* if a magnetic field of 35 Gauss (3.5mT) or greater is detected.
 
.. delphi:function:: function TBrickletHallEffect.GetEdgeCount(const resetCounter: boolean): longword

 Returns the current value of the edge counter. You can configure
 edge type (rising, falling, both) that is counted with
 :delphi:func:`SetEdgeCountConfig <TBrickletHallEffect.SetEdgeCountConfig>`.
 
 If you set the reset counter to *true*, the count is set back to 0
 directly after it is read.
 


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

.. delphi:function:: procedure TBrickletHallEffect.SetEdgeCountConfig(const edgeType: byte; const debounce: byte)

 The edge type parameter configures if rising edges, falling edges or 
 both are counted. Possible edge types are:
 
 * 0 = rising (default)
 * 1 = falling
 * 2 = both
 
 A magnetic field of 35 Gauss (3.5mT) or greater causes a falling edge and a
 magnetic field of 25 Gauss (2.5mT) or smaller causes a rising edge.
 
 If a magnet comes near the Bricklet the signal goes low (falling edge), if
 a magnet is removed from the vicinity the signal goes high (rising edge).
 
 The debounce time is given in ms.
 
 Configuring an edge counter resets its value to 0.
 
 If you don't know what any of this means, just leave it at default. The
 default configuration is very likely OK for you.
 
 Default values: 0 (edge type) and 100ms (debounce time)
 
 The following constants are available for this function:
 
 * BRICKLET_HALL_EFFECT_EDGE_TYPE_RISING = 0
 * BRICKLET_HALL_EFFECT_EDGE_TYPE_FALLING = 1
 * BRICKLET_HALL_EFFECT_EDGE_TYPE_BOTH = 2
 
.. delphi:function:: procedure TBrickletHallEffect.GetEdgeCountConfig(out edgeType: byte; out debounce: byte)

 Returns the edge type and debounce time as set by :delphi:func:`SetEdgeCountConfig <TBrickletHallEffect.SetEdgeCountConfig>`.
 
 The following constants are available for this function:
 
 * BRICKLET_HALL_EFFECT_EDGE_TYPE_RISING = 0
 * BRICKLET_HALL_EFFECT_EDGE_TYPE_FALLING = 1
 * BRICKLET_HALL_EFFECT_EDGE_TYPE_BOTH = 2
 
.. delphi:function:: function TBrickletHallEffect.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 TBrickletHallEffect.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 <TBrickletHallEffect.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 <TBrickletHallEffect.SetResponseExpected>`
 for the list of function ID constants available for this function.
 
.. delphi:function:: procedure TBrickletHallEffect.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_HALL_EFFECT_FUNCTION_SET_EDGE_COUNT_CONFIG = 3
 * BRICKLET_HALL_EFFECT_FUNCTION_SET_EDGE_INTERRUPT = 5
 * BRICKLET_HALL_EFFECT_FUNCTION_SET_EDGE_COUNT_CALLBACK_PERIOD = 7
 
.. delphi:function:: procedure TBrickletHallEffect.SetResponseExpectedAll(const responseExpected: boolean)

 Changes the response expected flag for all setter and callback configuration
 functions of this device at once.
 
.. delphi:function:: procedure TBrickletHallEffect.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 TBrickletHallEffect.SetEdgeInterrupt(const edges: longword)

 Sets the number of edges until an interrupt is invoked.
 
 If *edges* is set to n, an interrupt is invoked for every n-th detected edge.
 
 If *edges* is set to 0, the interrupt is disabled.
 
 Default value is 0.
 
.. delphi:function:: function TBrickletHallEffect.GetEdgeInterrupt(): longword

 Returns the edges as set by :delphi:func:`SetEdgeInterrupt <TBrickletHallEffect.SetEdgeInterrupt>`.
 
.. delphi:function:: procedure TBrickletHallEffect.SetEdgeCountCallbackPeriod(const period: longword)

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

 Returns the period as set by :delphi:func:`SetEdgeCountCallbackPeriod <TBrickletHallEffect.SetEdgeCountCallbackPeriod>`.
 




.. _hall_effect_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: TBrickletHallEffect; const param: word);
  begin
    WriteLn(param);
  end;

  hallEffect.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 TBrickletHallEffect.OnEdgeCount

 .. code-block:: delphi

  procedure(sender: TBrickletHallEffect; const count: longword; const value: boolean) of object;


 This callback is triggered periodically with the period that is set by
 :delphi:func:`SetEdgeCountCallbackPeriod <TBrickletHallEffect.SetEdgeCountCallbackPeriod>`. The parameters are the
 current count and the current value (see :delphi:func:`GetValue <TBrickletHallEffect.GetValue>` and :delphi:func:`GetEdgeCount <TBrickletHallEffect.GetEdgeCount>`).
 
 :delphi:func:`OnEdgeCount <TBrickletHallEffect.OnEdgeCount>` is only triggered if the count or value changed since the
 last triggering.
 


.. _hall_effect_bricklet_delphi_constants:

Constants
^^^^^^^^^

.. delphi:function:: const BRICKLET_HALL_EFFECT_DEVICE_IDENTIFIER

 This constant is used to identify a Hall Effect Bricklet.

 The :delphi:func:`GetIdentity <TBrickletHallEffect.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.

