Python - Accelerometer Bricklet – Tinkerforge

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# Python - Accelerometer 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 Python API bindings for the Accelerometer Bricklet. General information and technical specifications for the Accelerometer Bricklet are summarized in its hardware description.

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

## Examples

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

### Simple

Download (example_simple.py)

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    #!/usr/bin/env python
    # -*- coding: utf-8 -*-

    HOST = "localhost"
    PORT = 4223
    UID = "abc" # Change to your UID

    import time

    from tinkerforge.ip_connection import IPConnection
    from tinkerforge.bricklet_accelerometer import Accelerometer

    if __name__ == "__main__":
        ipcon = IPConnection() # Create IP connection
        acc = Accelerometer(UID, ipcon) # Create device object

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

        # Get Acceleration (unit is 1/1000 G)
        acceleration = acc.get_acceleration()

        print('Acceleration: x -> {0}G, y -> {1}G, z -> {2}G'.format(acceleration.x / 1000.0,
                                                                     acceleration.y / 1000.0,
                                                                     acceleration.z / 1000.0))

        raw_input('Press key to exit\n') # Use input() in Python 3
        ipcon.disconnect()

### Callback

Download (example_callback.py)

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    #!/usr/bin/env python
    # -*- coding: utf-8 -*-

    HOST = "localhost"
    PORT = 4223
    UID = "abc" # Change to your UID

    from tinkerforge.ip_connection import IPConnection
    from tinkerforge.bricklet_accelerometer import Accelerometer

    # Callback function for acceleration callback
    def cb_acceleration(x, y, z):
        print('Acceleration: x -> {0}G, y -> {1}G, z -> {2}G'.format(x / 1000.0,
                                                                     y / 1000.0,
                                                                     z / 1000.0))

    if __name__ == "__main__":
        ipcon = IPConnection() # Create IP connection
        acc = Accelerometer(UID, ipcon) # Create device object

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

        # Set Period for acceleration callback to 0.1s (100ms)
        # Note: The callback is only called every second if the
        #       acceleration has changed since the last call!
        acc.set_acceleration_callback_period(100)

        # Register acceleration callback to function cb_acceleration
        acc.register_callback(acc.CALLBACK_ACCELERATION, cb_acceleration)

        raw_input('Press key to exit\n') # Use input() in Python 3
        ipcon.disconnect()

### Threshold

Download (example_threshold.py)

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    #!/usr/bin/env python
    # -*- coding: utf-8 -*-

    HOST = "localhost"
    PORT = 4223
    UID = "abc" # Change to your UID

    from tinkerforge.ip_connection import IPConnection
    from tinkerforge.bricklet_accelerometer import Accelerometer

    # Callback function for acceleration callback
    # Turn LED on if acceleration goes above 3G
    def cb_reached(acc, x, y, z):
        acc.led_on()

    if __name__ == "__main__":
        ipcon = IPConnection() # Create IP connection
        acc = Accelerometer(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 1 seconds (1000ms)
        acc.set_debounce_period(1000)

        # Register threshold reached callback to function cb_reached
        func = lambda x, y, z: cb_reached(acc, x, y, z)
        acc.register_callback(acc.CALLBACK_ACCELERATION_REACHED, func)

        # Configure threshold for acceleration values,
        # Trigger callback if one of the accelerations goes above 3G
        acc.set_acceleration_callback_threshold('>', 3000, 0, 3000, 0, 3000, 0)

        raw_input('Press key to exit\n') # Use input() in Python 3
        ipcon.disconnect()

## API

Generally, every method of the Python bindings can throw an `tinkerforge.ip_connection.Error` exception that has a `value` and a `description` property. `value` can have different values:

- Error.TIMEOUT = -1
- Error.ALREADY_CONNECTED = -7
- Error.NOT_CONNECTED = -8
- Error.INVALID_PARAMETER = -9
- Error.NOT_SUPPORTED = -10
- Error.UNKNOWN_ERROR_CODE = -11

All methods listed below are thread-safe.

### Basic Functions

`Accelerometer`(uid, ipcon)

  Parameters:

  - uid -- string
  - ipcon -- IPConnection

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

      accelerometer = Accelerometer("YOUR_DEVICE_UID", ipcon)

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

`Accelerometer.``get_acceleration`()

  Return type: | (int, int, int)

  Returns the acceleration in x, y and z direction. The values are given in mG (1/1000 G).

  If you want to get the acceleration periodically, it is recommended to use the callback `CALLBACK_ACCELERATION` and set the period with `set_acceleration_callback_period()`.

  The returned namedtuple has the variables `x`, `y` and `z`.

`Accelerometer.``get_temperature`()

  Return type: | int

  Returns the temperature of the accelerometer in °C.

`Accelerometer.``led_on`()

  Return type: | None

  Enables the LED on the Bricklet.

`Accelerometer.``led_off`()

  Return type: | None

  Disables the LED on the Bricklet.

`Accelerometer.``is_led_on`()

  Return type: | int

  Returns true if the LED is enabled, false otherwise.

### Advanced Functions

`Accelerometer.``set_configuration`(data_rate, full_scale, filter_bandwidth)

  Parameters:

  - data_rate -- int
  - full_scale -- int
  - filter_bandwidth -- int

  Return type: | None

  Configures the data rate, full scale range and filter bandwidth. Possible values are:

  - Data rate of 0Hz to 1600Hz.
  - Full scale range of -2G to +2G up to -16G to +16G.
  - Filter bandwidth between 50Hz and 800Hz.

  Decreasing data rate or full scale range will also decrease the noise on the data.

  The default values are 100Hz data rate, -4G to +4G range and 200Hz filter bandwidth.

  The following constants are available for this function:

  - Accelerometer.DATA_RATE_OFF = 0
  - Accelerometer.DATA_RATE_3HZ = 1
  - Accelerometer.DATA_RATE_6HZ = 2
  - Accelerometer.DATA_RATE_12HZ = 3
  - Accelerometer.DATA_RATE_25HZ = 4
  - Accelerometer.DATA_RATE_50HZ = 5
  - Accelerometer.DATA_RATE_100HZ = 6
  - Accelerometer.DATA_RATE_400HZ = 7
  - Accelerometer.DATA_RATE_800HZ = 8
  - Accelerometer.DATA_RATE_1600HZ = 9
  - Accelerometer.FULL_SCALE_2G = 0
  - Accelerometer.FULL_SCALE_4G = 1
  - Accelerometer.FULL_SCALE_6G = 2
  - Accelerometer.FULL_SCALE_8G = 3
  - Accelerometer.FULL_SCALE_16G = 4
  - Accelerometer.FILTER_BANDWIDTH_800HZ = 0
  - Accelerometer.FILTER_BANDWIDTH_400HZ = 1
  - Accelerometer.FILTER_BANDWIDTH_200HZ = 2
  - Accelerometer.FILTER_BANDWIDTH_50HZ = 3

`Accelerometer.``get_configuration`()

  Return type: | (int, int, int)

  Returns the configuration as set by `set_configuration()`.

  The following constants are available for this function:

  - Accelerometer.DATA_RATE_OFF = 0
  - Accelerometer.DATA_RATE_3HZ = 1
  - Accelerometer.DATA_RATE_6HZ = 2
  - Accelerometer.DATA_RATE_12HZ = 3
  - Accelerometer.DATA_RATE_25HZ = 4
  - Accelerometer.DATA_RATE_50HZ = 5
  - Accelerometer.DATA_RATE_100HZ = 6
  - Accelerometer.DATA_RATE_400HZ = 7
  - Accelerometer.DATA_RATE_800HZ = 8
  - Accelerometer.DATA_RATE_1600HZ = 9
  - Accelerometer.FULL_SCALE_2G = 0
  - Accelerometer.FULL_SCALE_4G = 1
  - Accelerometer.FULL_SCALE_6G = 2
  - Accelerometer.FULL_SCALE_8G = 3
  - Accelerometer.FULL_SCALE_16G = 4
  - Accelerometer.FILTER_BANDWIDTH_800HZ = 0
  - Accelerometer.FILTER_BANDWIDTH_400HZ = 1
  - Accelerometer.FILTER_BANDWIDTH_200HZ = 2
  - Accelerometer.FILTER_BANDWIDTH_50HZ = 3

  The returned namedtuple has the variables `data_rate`, `full_scale` and `filter_bandwidth`.

`Accelerometer.``get_api_version`()

  Return type: | [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.

`Accelerometer.``get_response_expected`(function_id)

  Parameters: | function_id -- int
  Return type: | bool

  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.

`Accelerometer.``set_response_expected`(function_id, response_expected)

  Parameters:

  - function_id -- int
  - response_expected -- bool

  Return type: | None

  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:

  - Accelerometer.FUNCTION_SET_ACCELERATION_CALLBACK_PERIOD = 2
  - Accelerometer.FUNCTION_SET_ACCELERATION_CALLBACK_THRESHOLD = 4
  - Accelerometer.FUNCTION_SET_DEBOUNCE_PERIOD = 6
  - Accelerometer.FUNCTION_SET_CONFIGURATION = 9
  - Accelerometer.FUNCTION_LED_ON = 11
  - Accelerometer.FUNCTION_LED_OFF = 12

`Accelerometer.``set_response_expected_all`(response_expected)

  Parameters: | response_expected -- bool
  Return type: | None

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

`Accelerometer.``get_identity`()

  Return type: | (str, str, chr, [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 namedtuple has the variables `uid`, `connected_uid`, `position`, `hardware_version`, `firmware_version` and `device_identifier`.

### Callback Configuration Functions

`Accelerometer.``register_callback`(id, callback)

  Parameters:

  - id -- int
  - callback -- callable

  Return type: | None

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

`Accelerometer.``set_acceleration_callback_period`(period)

  Parameters: | period -- int
  Return type: | None

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

  `CALLBACK_ACCELERATION` is only triggered if the acceleration has changed since the last triggering.

  The default value is 0.

`Accelerometer.``get_acceleration_callback_period`()

  Return type: | int

  Returns the period as set by `set_acceleration_callback_period()`.

`Accelerometer.``set_acceleration_callback_threshold`(option, min_x, max_x, min_y, max_y, min_z, max_z)

  Parameters:

  - option -- chr
  - min_x -- int
  - max_x -- int
  - min_y -- int
  - max_y -- int
  - min_z -- int
  - max_z -- int

  Return type: | None

  Sets the thresholds for the `CALLBACK_ACCELERATION_REACHED` callback.

  The following options are possible:

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

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

  The following constants are available for this function:

  - Accelerometer.THRESHOLD_OPTION_OFF = 'x'
  - Accelerometer.THRESHOLD_OPTION_OUTSIDE = 'o'
  - Accelerometer.THRESHOLD_OPTION_INSIDE = 'i'
  - Accelerometer.THRESHOLD_OPTION_SMALLER = '<'
  - Accelerometer.THRESHOLD_OPTION_GREATER = '>'

`Accelerometer.``get_acceleration_callback_threshold`()

  Return type: | (chr, int, int, int, int, int, int)

  Returns the threshold as set by `set_acceleration_callback_threshold()`.

  The following constants are available for this function:

  - Accelerometer.THRESHOLD_OPTION_OFF = 'x'
  - Accelerometer.THRESHOLD_OPTION_OUTSIDE = 'o'
  - Accelerometer.THRESHOLD_OPTION_INSIDE = 'i'
  - Accelerometer.THRESHOLD_OPTION_SMALLER = '<'
  - Accelerometer.THRESHOLD_OPTION_GREATER = '>'

  The returned namedtuple has the variables `option`, `min_x`, `max_x`, `min_y`, `max_y`, `min_z` and `max_z`.

`Accelerometer.``set_debounce_period`(debounce)

  Parameters: | debounce -- int
  Return type: | None

  Sets the period in ms with which the threshold callback

  - `CALLBACK_ACCELERATION_REACHED`

  is triggered, if the threshold

  - `set_acceleration_callback_threshold()`

  keeps being reached.

  The default value is 100.

`Accelerometer.``get_debounce_period`()

  Return type: | 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 the callback function:

    def my_callback(param):
        print(param)

    accelerometer.register_callback(Accelerometer.CALLBACK_EXAMPLE, my_callback)

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.

`Accelerometer.``CALLBACK_ACCELERATION`

  Parameters:

  - x -- int
  - y -- int
  - z -- int

  This callback is triggered periodically with the period that is set by `set_acceleration_callback_period()`. The parameters are the X, Y and Z acceleration.

  `CALLBACK_ACCELERATION` is only triggered if the acceleration has changed since the last triggering.

`Accelerometer.``CALLBACK_ACCELERATION_REACHED`

  Parameters:

  - x -- int
  - y -- int
  - z -- int

  This callback is triggered when the threshold as set by `set_acceleration_callback_threshold()` is reached. The parameters are the X, Y and Z acceleration.

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

### Constants

`Accelerometer.``DEVICE_IDENTIFIER`

  This constant is used to identify a Accelerometer 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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