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:orphan:
:breadcrumbs: <a href="../../index.html">Home</a> / <a href="../../index.html#software-php">Software</a> / PHP - Load Cell Bricklet

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

.. _load_cell_bricklet_php:

PHP - Load Cell 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:`PHP API bindings <api_bindings_php>` for the :ref:`Load Cell Bricklet <load_cell_bricklet>`. General information and technical
specifications for the Load Cell Bricklet are summarized in its :ref:`hardware description
<load_cell_bricklet_description>`.

An :ref:`installation guide <api_bindings_php_install>` for the PHP API
bindings is part of their general description.

.. _load_cell_bricklet_php_examples:


Examples
--------

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

.. _load_cell_bricklet_php_api:

API
---

Functions that return multiple values return them in an associative array.




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


.. php:function:: class BrickletLoadCell(string $uid, IPConnection $ipcon)

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

 .. code-block:: php

    <?php   $load_cell = new BrickletLoadCell('YOUR_DEVICE_UID', $ipcon);   ?>

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


.. php:function:: int BrickletLoadCell::getWeight()

 Returns the currently measured weight in grams.
 
 If you want to get the weight periodically, it is recommended 
 to use the callback :php:member:`CALLBACK_WEIGHT <BrickletLoadCell::CALLBACK_WEIGHT>` and set the period with 
 :php:func:`setWeightCallbackPeriod() <BrickletLoadCell::setWeightCallbackPeriod>`.
 
.. php:function:: void BrickletLoadCell::ledOn()

 Turns the LED on.
 
.. php:function:: void BrickletLoadCell::ledOff()

 Turns the LED off.
 
.. php:function:: int BrickletLoadCell::isLEDOn()

 Returns *true* if the led is on, *false* otherwise.
 
.. php:function:: void BrickletLoadCell::tare()

 Sets the currently measured weight as tare weight.
 


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

.. php:function:: void BrickletLoadCell::setMovingAverage(int $average)

 Sets the length of a `moving averaging <http://en.wikipedia.org/wiki/Moving_average>`__ 
 for the weight 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 1-40.
 
 The default value is 4.
 
.. php:function:: int BrickletLoadCell::getMovingAverage()

 Returns the length moving average as set by :php:func:`setMovingAverage() <BrickletLoadCell::setMovingAverage>`.
 
.. php:function:: void BrickletLoadCell::calibrate(int $weight)

 To calibrate your Load Cell Bricklet you have to
 
 * empty the scale and call this function with 0 and
 * add a known weight to the scale and call this function with the weight in 
   grams.
 
 The calibration is saved in the EEPROM of the Bricklet and only
 needs to be done once.
 
 We recommend to use the Brick Viewer for calibration, you don't need
 to call this function in your source code.
 
.. php:function:: void BrickletLoadCell::setConfiguration(int $rate, int $gain)

 The measurement rate and gain are configurable.
 
 The rate can be either 10Hz or 80Hz. A faster rate will produce more noise.
 It is additionally possible to add a moving average
 (see :php:func:`setMovingAverage() <BrickletLoadCell::setMovingAverage>`) to the measurements.
 
 The gain can be 128x, 64x or 32x. It represents a measurement range of
 ±20mV, ±40mV and ±80mV respectively. The Load Cell Bricklet uses an
 excitation voltage of 5V and most load cells use an output of 2mV/V. That
 means the voltage range is ±15mV for most load cells (i.e. gain of 128x
 is best). If you don't know what all of this means you should keep it at 
 128x, it will most likely be correct.
 
 The configuration is saved in the EEPROM of the Bricklet and only
 needs to be done once.
 
 We recommend to use the Brick Viewer for configuration, you don't need
 to call this function in your source code.
 
 The default rate is 10Hz and the default gain is 128x.
 
 The following constants are available for this function:
 
 * BrickletLoadCell::RATE_10HZ = 0
 * BrickletLoadCell::RATE_80HZ = 1
 * BrickletLoadCell::GAIN_128X = 0
 * BrickletLoadCell::GAIN_64X = 1
 * BrickletLoadCell::GAIN_32X = 2
 
.. php:function:: array BrickletLoadCell::getConfiguration()

 Returns the configuration as set by :php:func:`setConfiguration() <BrickletLoadCell::setConfiguration>`.
 
 The following constants are available for this function:
 
 * BrickletLoadCell::RATE_10HZ = 0
 * BrickletLoadCell::RATE_80HZ = 1
 * BrickletLoadCell::GAIN_128X = 0
 * BrickletLoadCell::GAIN_64X = 1
 * BrickletLoadCell::GAIN_32X = 2
 
 The returned array has the keys ``rate`` and ``gain``.

.. php:function:: array BrickletLoadCell::getAPIVersion()

 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.
 
.. php:function:: bool BrickletLoadCell::getResponseExpected(int $function_id)

 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
 :php:func:`setResponseExpected() <BrickletLoadCell::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 :php:func:`setResponseExpected() <BrickletLoadCell::setResponseExpected>`
 for the list of function ID constants available for this function.
 
.. php:function:: void BrickletLoadCell::setResponseExpected(int $function_id, bool $response_expected)

 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:
 
 * BrickletLoadCell::FUNCTION_SET_WEIGHT_CALLBACK_PERIOD = 2
 * BrickletLoadCell::FUNCTION_SET_WEIGHT_CALLBACK_THRESHOLD = 4
 * BrickletLoadCell::FUNCTION_SET_DEBOUNCE_PERIOD = 6
 * BrickletLoadCell::FUNCTION_SET_MOVING_AVERAGE = 8
 * BrickletLoadCell::FUNCTION_LED_ON = 10
 * BrickletLoadCell::FUNCTION_LED_OFF = 11
 * BrickletLoadCell::FUNCTION_CALIBRATE = 13
 * BrickletLoadCell::FUNCTION_TARE = 14
 * BrickletLoadCell::FUNCTION_SET_CONFIGURATION = 15
 
.. php:function:: void BrickletLoadCell::setResponseExpectedAll(bool $response_expected)

 Changes the response expected flag for all setter and callback configuration
 functions of this device at once.
 
.. php:function:: array BrickletLoadCell::getIdentity()

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



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


.. php:function:: void BrickletLoadCell::registerCallback(int $id, callable $callback, mixed $userData = NULL)

 Registers a callback with ID *$id* to the callable *$callback*.
 The *$userData*  will be given as a parameter of the callback.

 The available  IDs with corresponding function signatures are listed
 :ref:`below <load_cell_bricklet_php_callbacks>`.


.. php:function:: void BrickletLoadCell::setWeightCallbackPeriod(int $period)

 Sets the period in ms with which the :php:member:`CALLBACK_WEIGHT <BrickletLoadCell::CALLBACK_WEIGHT>` callback is triggered
 periodically. A value of 0 turns the callback off.
 
 :php:member:`CALLBACK_WEIGHT <BrickletLoadCell::CALLBACK_WEIGHT>` is only triggered if the weight has changed since the
 last triggering.
 
 The default value is 0.
 
.. php:function:: int BrickletLoadCell::getWeightCallbackPeriod()

 Returns the period as set by :php:func:`setWeightCallbackPeriod() <BrickletLoadCell::setWeightCallbackPeriod>`.
 
.. php:function:: void BrickletLoadCell::setWeightCallbackThreshold(string $option, int $min, int $max)

 Sets the thresholds for the :php:member:`CALLBACK_WEIGHT_REACHED <BrickletLoadCell::CALLBACK_WEIGHT_REACHED>` 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 weight is *outside* the min and max values"
  "'i'",    "Callback is triggered when the weight is *inside* the min and max values"
  "'<'",    "Callback is triggered when the weight is smaller than the min value (max is ignored)"
  "'>'",    "Callback is triggered when the weight is greater than the min value (max is ignored)"
 
 The default value is ('x', 0, 0).
 
 The following constants are available for this function:
 
 * BrickletLoadCell::THRESHOLD_OPTION_OFF = 'x'
 * BrickletLoadCell::THRESHOLD_OPTION_OUTSIDE = 'o'
 * BrickletLoadCell::THRESHOLD_OPTION_INSIDE = 'i'
 * BrickletLoadCell::THRESHOLD_OPTION_SMALLER = '<'
 * BrickletLoadCell::THRESHOLD_OPTION_GREATER = '>'
 
.. php:function:: array BrickletLoadCell::getWeightCallbackThreshold()

 Returns the threshold as set by :php:func:`setWeightCallbackThreshold() <BrickletLoadCell::setWeightCallbackThreshold>`.
 
 The following constants are available for this function:
 
 * BrickletLoadCell::THRESHOLD_OPTION_OFF = 'x'
 * BrickletLoadCell::THRESHOLD_OPTION_OUTSIDE = 'o'
 * BrickletLoadCell::THRESHOLD_OPTION_INSIDE = 'i'
 * BrickletLoadCell::THRESHOLD_OPTION_SMALLER = '<'
 * BrickletLoadCell::THRESHOLD_OPTION_GREATER = '>'
 
 The returned array has the keys ``option``, ``min`` and ``max``.

.. php:function:: void BrickletLoadCell::setDebouncePeriod(int $debounce)

 Sets the period in ms with which the threshold callback
 
 * :php:member:`CALLBACK_WEIGHT_REACHED <BrickletLoadCell::CALLBACK_WEIGHT_REACHED>`
 
 is triggered, if the threshold
 
 * :php:func:`setWeightCallbackThreshold() <BrickletLoadCell::setWeightCallbackThreshold>`
 
 keeps being reached.
 
 The default value is 100.
 
.. php:function:: int BrickletLoadCell::getDebouncePeriod()

 Returns the debounce period as set by :php:func:`setDebouncePeriod() <BrickletLoadCell::setDebouncePeriod>`.
 


.. _load_cell_bricklet_php_callbacks:

Callbacks
^^^^^^^^^

Callbacks can be registered to receive
time critical or recurring data from the device. The registration is done
with the :php:func:`registerCallback() <BrickletLoadCell::registerCallback>` function of
the device object. The first parameter is the callback ID and the second
parameter the callback function:

.. code-block:: php

    <?php

    function myCallback($param)
    {
        echo $param . "\n";
    }

    $load_cell->registerCallback(BrickletLoadCell::CALLBACK_EXAMPLE, 'myCallback');

    ?>

The available constants with corresponding function signatures 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.

.. php:member:: int BrickletLoadCell::CALLBACK_WEIGHT

 .. code-block:: php

  <?php   void callback(int $weight [, mixed $userData])   ?>

 This callback is triggered periodically with the period that is set by
 :php:func:`setWeightCallbackPeriod() <BrickletLoadCell::setWeightCallbackPeriod>`. The parameter is the weight
 as measured by the load cell.
 
 :php:member:`CALLBACK_WEIGHT <BrickletLoadCell::CALLBACK_WEIGHT>` is only triggered if the weight has changed since the
 last triggering.
 
.. php:member:: int BrickletLoadCell::CALLBACK_WEIGHT_REACHED

 .. code-block:: php

  <?php   void callback(int $weight [, mixed $userData])   ?>

 This callback is triggered when the threshold as set by
 :php:func:`setWeightCallbackThreshold() <BrickletLoadCell::setWeightCallbackThreshold>` is reached.
 The parameter is the weight as measured by the load cell.
 
 If the threshold keeps being reached, the callback is triggered periodically
 with the period as set by :php:func:`setDebouncePeriod() <BrickletLoadCell::setDebouncePeriod>`.
 


.. _load_cell_bricklet_php_constants:

Constants
^^^^^^^^^

.. php:member:: int BrickletLoadCell::DEVICE_IDENTIFIER

 This constant is used to identify a Load Cell Bricklet.

 The :php:func:`getIdentity() <BrickletLoadCell::getIdentity>` function and the
 :php:member:`CALLBACK_ENUMERATE <IPConnection::CALLBACK_ENUMERATE>`
 callback of the IP Connection have a ``deviceIdentifier`` parameter to specify
 the Brick's or Bricklet's type.

