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

.. |device_identifier_constant| unicode:: 0xA0
   :trim:

.. _load_cell_bricklet_shell:

Shell - 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:`Shell API bindings <api_bindings_shell>` 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_shell_install>` for the Shell API
bindings is part of their general description.

.. _load_cell_bricklet_shell_examples:


Examples
--------

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

.. _load_cell_bricklet_shell_api:

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
:ref:`here <ipcon_shell_api>`. The specific command structure is shown below.

.. sh:function:: X Stinkerforge Pcall Nload-cell-bricklet A[<option>..] L<uid> L<function> L[<argument>..]

 :param <uid>: string
 :param <function>: string

 The ``call`` command is used to call a function of the Load Cell 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 Load Cell Bricklet and exits


.. sh:function:: X Stinkerforge Pdispatch Nload-cell-bricklet A[<option>..] L<uid> L<callback>

 :param <uid>: string
 :param <callback>: string

 The ``dispatch`` command is used to dispatch a callback of the Load Cell 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 Load Cell Bricklet and exits


.. sh:function:: X Stinkerforge Scall Pload-cell-bricklet L<uid> N<function> A[<option>..] L[<argument>..]

 :param <uid>: string
 :param <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 :ref:`output formatting <ipcon_shell_output>`
   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.


.. sh:function:: X Stinkerforge Sdispatch Pload-cell-bricklet L<uid> N<callback> A[<option>..]

 :param <uid>: string
 :param <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 :ref:`output formatting <ipcon_shell_output>`
   for details)



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



.. sh:function:: tinkerforge call load-cell-bricklet <uid> get-weight  


 :returns weight: int

 Returns the currently measured weight in grams.
 
 If you want to get the weight periodically, it is recommended 
 to use the callback :sh:func:`weight <load-cell-bricklet weight>` and set the period with 
 :sh:func:`set-weight-callback-period <load-cell-bricklet set-weight-callback-period>`.
 
.. sh:function:: tinkerforge call load-cell-bricklet <uid> led-on  


 :noreturn: no output

 Turns the LED on.
 
.. sh:function:: tinkerforge call load-cell-bricklet <uid> led-off  


 :noreturn: no output

 Turns the LED off.
 
.. sh:function:: tinkerforge call load-cell-bricklet <uid> is-led-on  


 :returns value: int

 Returns *true* if the led is on, *false* otherwise.
 
.. sh:function:: tinkerforge call load-cell-bricklet <uid> tare  


 :noreturn: no output

 Sets the currently measured weight as tare weight.
 


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

.. sh:function:: tinkerforge call load-cell-bricklet <uid> set-moving-average <average> 

 :param <average>: int

 :noreturn: no output

 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.
 
.. sh:function:: tinkerforge call load-cell-bricklet <uid> get-moving-average  


 :returns average: int

 Returns the length moving average as set by :sh:func:`set-moving-average <load-cell-bricklet set-moving-average>`.
 
.. sh:function:: tinkerforge call load-cell-bricklet <uid> calibrate <weight> 

 :param <weight>: int

 :noreturn: no output

 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.
 
.. sh:function:: tinkerforge call load-cell-bricklet <uid> set-configuration <rate> <gain> 

 :param <rate>: int (has symbols)
 :param <gain>: int (has symbols)

 :noreturn: no output

 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 :sh:func:`set-moving-average <load-cell-bricklet set-moving-average>`) 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 symbols are available for this function:
 
 * ``10hz`` = 0, for <rate>
 * ``80hz`` = 1, for <rate>
 * ``128x`` = 0, for <gain>
 * ``64x`` = 1, for <gain>
 * ``32x`` = 2, for <gain>
 
.. sh:function:: tinkerforge call load-cell-bricklet <uid> get-configuration  


 :returns rate: int (has symbols)
 :returns gain: int (has symbols)

 Returns the configuration as set by :sh:func:`set-configuration <load-cell-bricklet set-configuration>`.
 
 The following symbols are available for this function:
 
 * ``10hz`` = 0, for rate
 * ``80hz`` = 1, for rate
 * ``128x`` = 0, for gain
 * ``64x`` = 1, for gain
 * ``32x`` = 2, for gain
 
.. sh:function:: tinkerforge call load-cell-bricklet <uid> get-identity  


 :returns uid: string
 :returns connected-uid: string
 :returns position: char
 :returns hardware-version: int,int,int
 :returns firmware-version: int,int,int
 :returns 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 :ref:`here <device_identifier>`.
 |device_identifier_constant|
 


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



.. sh:function:: tinkerforge call load-cell-bricklet <uid> set-weight-callback-period <period> 

 :param <period>: int

 :noreturn: no output

 Sets the period in ms with which the :sh:func:`weight <load-cell-bricklet weight>` callback is triggered
 periodically. A value of 0 turns the callback off.
 
 :sh:func:`weight <load-cell-bricklet weight>` is only triggered if the weight has changed since the
 last triggering.
 
 The default value is 0.
 
.. sh:function:: tinkerforge call load-cell-bricklet <uid> get-weight-callback-period  


 :returns period: int

 Returns the period as set by :sh:func:`set-weight-callback-period <load-cell-bricklet set-weight-callback-period>`.
 
.. sh:function:: tinkerforge call load-cell-bricklet <uid> set-weight-callback-threshold <option> <min> <max> 

 :param <option>: char (has symbols)
 :param <min>: int
 :param <max>: int

 :noreturn: no output

 Sets the thresholds for the :sh:func:`weight-reached <load-cell-bricklet 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 symbols are available for this function:
 
 * ``off`` = x, for <option>
 * ``outside`` = o, for <option>
 * ``inside`` = i, for <option>
 * ``smaller`` = <, for <option>
 * ``greater`` = >, for <option>
 
.. sh:function:: tinkerforge call load-cell-bricklet <uid> get-weight-callback-threshold  


 :returns option: char (has symbols)
 :returns min: int
 :returns max: int

 Returns the threshold as set by :sh:func:`set-weight-callback-threshold <load-cell-bricklet set-weight-callback-threshold>`.
 
 The following symbols are available for this function:
 
 * ``off`` = x, for option
 * ``outside`` = o, for option
 * ``inside`` = i, for option
 * ``smaller`` = <, for option
 * ``greater`` = >, for option
 
.. sh:function:: tinkerforge call load-cell-bricklet <uid> set-debounce-period <debounce> 

 :param <debounce>: int

 :noreturn: no output

 Sets the period in ms with which the threshold callback
 
 * :sh:func:`weight-reached <load-cell-bricklet weight-reached>`
 
 is triggered, if the threshold
 
 * :sh:func:`set-weight-callback-threshold <load-cell-bricklet set-weight-callback-threshold>`
 
 keeps being reached.
 
 The default value is 100.
 
.. sh:function:: tinkerforge call load-cell-bricklet <uid> get-debounce-period  


 :returns debounce: int

 Returns the debounce period as set by :sh:func:`set-debounce-period <load-cell-bricklet set-debounce-period>`.
 


.. _load_cell_bricklet_shell_callbacks:

Callbacks
^^^^^^^^^

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

.. code-block:: bash

    tinkerforge dispatch load-cell-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.

.. sh:function::  tinkerforge dispatch load-cell-bricklet <uid> weight

 :returns weight: int


 This callback is triggered periodically with the period that is set by
 :sh:func:`set-weight-callback-period <load-cell-bricklet set-weight-callback-period>`. The parameter is the weight
 as measured by the load cell.
 
 :sh:func:`weight <load-cell-bricklet weight>` is only triggered if the weight has changed since the
 last triggering.
 
.. sh:function::  tinkerforge dispatch load-cell-bricklet <uid> weight-reached

 :returns weight: int


 This callback is triggered when the threshold as set by
 :sh:func:`set-weight-callback-threshold <load-cell-bricklet set-weight-callback-threshold>` 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 :sh:func:`set-debounce-period <load-cell-bricklet set-debounce-period>`.
 


