Shell - Laser Range Finder Bricklet – Tinkerforge

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# Shell - Laser Range Finder 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 Shell API bindings for the Laser Range Finder Bricklet. General information and technical specifications for the Laser Range Finder Bricklet are summarized in its hardware description.

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

## Examples

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

### Simple

Download (example-simple.sh)

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    #!/bin/sh
    # connects to localhost:4223 by default, use --host and --port to change it

    # change to your UID
    uid=XYZ

    # Turn laser on and wait 250ms for very first measurement to be ready
    tinkerforge call laser-range-finder-bricklet $uid enable-laser
    sleep 1

    # get current distance (unit is cm/10)
    tinkerforge call laser-range-finder-bricklet $uid get-distance

### Callback

Download (example-callback.sh)

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    #!/bin/sh
    # connects to localhost:4223 by default, use --host and --port to change it

    # change to your UID
    uid=XYZ

    # Turn laser on and wait 250ms for very first measurement to be ready
    tinkerforge call laser-range-finder-bricklet $uid enable-laser
    sleep 1

    # set period for distance callback to 1s (1000ms)
    # note: the distance callback is only called every second if the
    #       distance has changed since the last call!
    tinkerforge call laser-range-finder-bricklet $uid set-distance-callback-period 1000

    # handle incoming distance callbacks (unit is cm)
    tinkerforge dispatch laser-range-finder-bricklet $uid distance

### Threshold

Download (example-threshold.sh)

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    #!/bin/sh
    # connects to localhost:4223 by default, use --host and --port to change it

    # change to your UID
    uid=XYZ

    # Turn laser on and wait 250ms for very first measurement to be ready
    tinkerforge call laser-range-finder-bricklet $uid enable-laser
    sleep 1

    # get threshold callbacks with a debounce time of 10 seconds (10000ms)
    tinkerforge call laser-range-finder-bricklet $uid set-debounce-period 10000

    # configure threshold for "greater than 20 cm" (unit is cm)
    tinkerforge call laser-range-finder-bricklet $uid set-distance-callback-threshold greater 20 0

    # handle incoming distance-reached callbacks (unit is cm)
    tinkerforge dispatch laser-range-finder-bricklet $uid distance-reached\
     --execute "echo Distance: {distance} cm"

## 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 here. The specific command structure is shown below.

tinkerforge `call` `laser-range-finder-bricklet` [<option>..] <uid> <function> [<argument>..]

  Parameters:

  - <uid> -- string
  - <function> -- string

  The `call` command is used to call a function of the Laser Range Finder 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 Laser Range Finder Bricklet and exits

tinkerforge `dispatch` `laser-range-finder-bricklet` [<option>..] <uid> <callback>

  Parameters:

  - <uid> -- string
  - <callback> -- string

  The `dispatch` command is used to dispatch a callback of the Laser Range Finder 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 Laser Range Finder Bricklet and exits

tinkerforge call `laser-range-finder-bricklet` <uid> `<function>` [<option>..] [<argument>..]

  Parameters:

  - <uid> -- string
  - <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 output formatting 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.

tinkerforge dispatch `laser-range-finder-bricklet` <uid> `<callback>` [<option>..]

  Parameters:

  - <uid> -- string
  - <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 output formatting for details)

### Basic Functions

tinkerforge call `laser-range-finder-bricklet` <uid> `get-distance`

  Output:

  - distance -- int

  Returns the measured distance. The value has a range of 0 to 4000 and is given in cm.

  The Laser Range Finder Bricklet knows different modes. Distances are only measured in the distance measurement mode, see `set-mode`. Also the laser has to be enabled, see `enable-laser`.

  If you want to get the distance periodically, it is recommended to use the callback `distance` and set the period with `set-distance-callback-period`.

tinkerforge call `laser-range-finder-bricklet` <uid> `get-velocity`

  Output:

  - velocity -- int

  Returns the measured velocity. The value has a range of 0 to 12700 and is given in 1/100 m/s.

  The Laser Range Finder Bricklet knows different modes. Velocity is only measured in the velocity measurement modes, see `set-mode`. Also the laser has to be enabled, see `enable-laser`.

  If you want to get the velocity periodically, it is recommended to use the callback `velocity` and set the period with `set-velocity-callback-period`.

tinkerforge call `laser-range-finder-bricklet` <uid> `set-mode` <mode>

  Parameters:

  - <mode> -- int (has symbols)

  Output: | no output

  The LIDAR has five different modes. One mode is for distance measurements and four modes are for velocity measurements with different ranges.

  The following modes are available:

  - 0: Distance is measured with resolution 1.0 cm and range 0-400 cm
  - 1: Velocity is measured with resolution 0.1 m/s and range is 0-12.7 m/s
  - 2: Velocity is measured with resolution 0.25 m/s and range is 0-31.75 m/s
  - 3: Velocity is measured with resolution 0.5 m/s and range is 0-63.5 m/s
  - 4: Velocity is measured with resolution 1.0 m/s and range is 0-127 m/s

  The default mode is 0 (distance is measured).

  The following symbols are available for this function:

  - `distance` = 0, for <mode>
  - `velocity-max-13ms` = 1, for <mode>
  - `velocity-max-32ms` = 2, for <mode>
  - `velocity-max-64ms` = 3, for <mode>
  - `velocity-max-127ms` = 4, for <mode>

tinkerforge call `laser-range-finder-bricklet` <uid> `get-mode`

  Output:

  - mode -- int (has symbols)

  Returns the mode as set by `set-mode`.

  The following symbols are available for this function:

  - `distance` = 0, for mode
  - `velocity-max-13ms` = 1, for mode
  - `velocity-max-32ms` = 2, for mode
  - `velocity-max-64ms` = 3, for mode
  - `velocity-max-127ms` = 4, for mode

tinkerforge call `laser-range-finder-bricklet` <uid> `enable-laser`

  Output: | no output

  Activates the laser of the LIDAR.

  We recommend that you wait 250ms after enabling the laser before the first call of `get-distance` to ensure stable measurements.

tinkerforge call `laser-range-finder-bricklet` <uid> `disable-laser`

  Output: | no output

  Deactivates the laser of the LIDAR.

tinkerforge call `laser-range-finder-bricklet` <uid> `is-laser-enabled`

  Output:

  - laser-enabled -- bool

  Returns true if the laser is enabled, false otherwise.

### Advanced Functions

tinkerforge call `laser-range-finder-bricklet` <uid> `set-moving-average` <distance-average-length> <velocity-average-length>

  Parameters:

  - <distance-average-length> -- int
  - <velocity-average-length> -- int

  Output: | no output

  Sets the length of a moving averaging for the distance and velocity.

  Setting the length to 0 will turn the averaging completely off. With less averaging, there is more noise on the data.

  The range for the averaging is 0-30.

  The default value is 10.

tinkerforge call `laser-range-finder-bricklet` <uid> `get-moving-average`

  Output:

  - distance-average-length -- int
  - velocity-average-length -- int

  Returns the length moving average as set by `set-moving-average`.

tinkerforge call `laser-range-finder-bricklet` <uid> `get-identity`

  Output:

  - uid -- string
  - connected-uid -- string
  - position -- char
  - hardware-version -- int,int,int
  - firmware-version -- int,int,int
  - 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 here.

### Callback Configuration Functions

tinkerforge call `laser-range-finder-bricklet` <uid> `set-distance-callback-period` <period>

  Parameters:

  - <period> -- int

  Output: | no output

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

  `distance` is only triggered if the distance value has changed since the last triggering.

  The default value is 0.

tinkerforge call `laser-range-finder-bricklet` <uid> `get-distance-callback-period`

  Output:

  - period -- int

  Returns the period as set by `set-distance-callback-period`.

tinkerforge call `laser-range-finder-bricklet` <uid> `set-velocity-callback-period` <period>

  Parameters:

  - <period> -- int

  Output: | no output

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

  `velocity` is only triggered if the velocity value has changed since the last triggering.

  The default value is 0.

tinkerforge call `laser-range-finder-bricklet` <uid> `get-velocity-callback-period`

  Output:

  - period -- int

  Returns the period as set by `set-velocity-callback-period`.

tinkerforge call `laser-range-finder-bricklet` <uid> `set-distance-callback-threshold` <option> <min> <max>

  Parameters:

  - <option> -- char (has symbols)
  - <min> -- int
  - <max> -- int

  Output: | no output

  Sets the thresholds for the `distance-reached` callback.

  The following options are possible:

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

tinkerforge call `laser-range-finder-bricklet` <uid> `get-distance-callback-threshold`

  Output:

  - option -- char (has symbols)
  - min -- int
  - max -- int

  Returns the threshold as set by `set-distance-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

tinkerforge call `laser-range-finder-bricklet` <uid> `set-velocity-callback-threshold` <option> <min> <max>

  Parameters:

  - <option> -- char (has symbols)
  - <min> -- int
  - <max> -- int

  Output: | no output

  Sets the thresholds for the `velocity-reached` callback.

  The following options are possible:

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

tinkerforge call `laser-range-finder-bricklet` <uid> `get-velocity-callback-threshold`

  Output:

  - option -- char (has symbols)
  - min -- int
  - max -- int

  Returns the threshold as set by `set-velocity-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

tinkerforge call `laser-range-finder-bricklet` <uid> `set-debounce-period` <debounce>

  Parameters:

  - <debounce> -- int

  Output: | no output

  Sets the period in ms with which the threshold callbacks

  - `distance-reached`,
  - `velocity-reached`,

  are triggered, if the thresholds

  - `set-distance-callback-threshold`,
  - `set-velocity-callback-threshold`,

  keep being reached.

  The default value is 100.

tinkerforge call `laser-range-finder-bricklet` <uid> `get-debounce-period`

  Output:

  - debounce -- int

  Returns the debounce period as set by `set-debounce-period`.

### Callbacks

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

    tinkerforge dispatch laser-range-finder-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.

tinkerforge dispatch `laser-range-finder-bricklet` <uid> `distance`

  Output:

  - distance -- int

  This callback is triggered periodically with the period that is set by `set-distance-callback-period`. The parameter is the distance value of the sensor.

  `distance` is only triggered if the distance value has changed since the last triggering.

tinkerforge dispatch `laser-range-finder-bricklet` <uid> `velocity`

  Output:

  - velocity -- int

  This callback is triggered periodically with the period that is set by `set-velocity-callback-period`. The parameter is the velocity value of the sensor.

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

tinkerforge dispatch `laser-range-finder-bricklet` <uid> `distance-reached`

  Output:

  - distance -- int

  This callback is triggered when the threshold as set by `set-distance-callback-threshold` is reached. The parameter is the distance value of the sensor.

  If the threshold keeps being reached, the callback is triggered periodically with the period as set by `set-debounce-period`.

tinkerforge dispatch `laser-range-finder-bricklet` <uid> `velocity-reached`

  Output:

  - velocity -- int

  This callback is triggered when the threshold as set by `set-velocity-callback-threshold` is reached. The parameter is the velocity value of the sensor.

  If the threshold keeps being reached, the callback is triggered periodically with the period as set by `set-debounce-period`.

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