Shell - Gas Detector Bricklet – Tinkerforge

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# Shell - Gas Detector 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 Gas Detector Bricklet. General information and technical specifications for the Gas Detector 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).

## 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` `gas-detector-bricklet` [<option>..] <uid> <function> [<argument>..]

  Parameters:

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

  The `call` command is used to call a function of the Gas Detector 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 Gas Detector Bricklet and exits

tinkerforge `dispatch` `gas-detector-bricklet` [<option>..] <uid> <callback>

  Parameters:

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

  The `dispatch` command is used to dispatch a callback of the Gas Detector 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 Gas Detector Bricklet and exits

tinkerforge call `gas-detector-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 `gas-detector-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 `gas-detector-bricklet` <uid> `get-value`

  Output:

  - value -- int

  Returns a value between 0 and 4095.

  See here for more information about the measurements.

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

### Advanced Functions

tinkerforge call `gas-detector-bricklet` <uid> `set-moving-average` <average>

  Parameters:

  - <average> -- int

  Output: | no output

  Sets the length of a moving averaging for the measured 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 1-100.

  The default value is 100.

tinkerforge call `gas-detector-bricklet` <uid> `get-moving-average`

  Output:

  - average -- int

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

tinkerforge call `gas-detector-bricklet` <uid> `set-detector-type` <detector-type>

  Parameters:

  - <detector-type> -- int (has symbols)

  Output: | no output

  Sets the detector type.

  The following types are currently supported.

  - Type 0: MQ2 and MQ5
  - Type 1: MQ3

  The detector type is written to the EEPROM of the Bricklet, so it only has to be set once.

  You can use the Brick Viewer to set the detector type, so you likely don't need to use this function in your source code.

  The default detector type is 0.

  The following symbols are available for this function:

  - `0` = 0, for <detector-type>
  - `1` = 1, for <detector-type>

tinkerforge call `gas-detector-bricklet` <uid> `get-detector-type`

  Output:

  - detector-type -- int (has symbols)

  Returns the detector type as set by `set-detector-type`.

  The following symbols are available for this function:

  - `0` = 0, for detector-type
  - `1` = 1, for detector-type

tinkerforge call `gas-detector-bricklet` <uid> `heater-on`

  Output: | no output

  Turns the internal heater on.

tinkerforge call `gas-detector-bricklet` <uid> `heater-off`

  Output: | no output

  Turns the internal heater off.

tinkerforge call `gas-detector-bricklet` <uid> `is-heater-on`

  Output:

  - heater -- bool

  Returns true if the heater is on, false otherwise.

tinkerforge call `gas-detector-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 `gas-detector-bricklet` <uid> `set-value-callback-period` <period>

  Parameters:

  - <period> -- int

  Output: | no output

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

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

  The default value is 0.

tinkerforge call `gas-detector-bricklet` <uid> `get-value-callback-period`

  Output:

  - period -- int

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

tinkerforge call `gas-detector-bricklet` <uid> `set-value-callback-threshold` <option> <min> <max>

  Parameters:

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

  Output: | no output

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

  The following options are possible:

  Option | Description
  --- | ---
  'x' | Callback is turned off
  'o' | Callback is triggered when the value value is outside the min and max values
  'i' | Callback is triggered when the value value is inside the min and max values
  '<' | Callback is triggered when the value value is smaller than the min value (max is ignored)
  '>' | Callback is triggered when the value 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 `gas-detector-bricklet` <uid> `get-value-callback-threshold`

  Output:

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

  Returns the threshold as set by `set-value-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 `gas-detector-bricklet` <uid> `set-debounce-period` <debounce>

  Parameters:

  - <debounce> -- int

  Output: | no output

  Sets the period in ms with which the threshold callback

  - `value-reached`

  is triggered, if the threshold

  - `set-value-callback-threshold`

  keeps being reached.

  The default value is 100.

tinkerforge call `gas-detector-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 gas-detector-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 `gas-detector-bricklet` <uid> `value`

  Output:

  - value -- int

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

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

tinkerforge dispatch `gas-detector-bricklet` <uid> `value-reached`

  Output:

  - value -- int

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

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

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