C/C++ - Gas Detector Bricklet – Tinkerforge

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# C/C++ - 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 C/C++ 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 C/C++ API bindings is part of their general description.

## Examples

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

## API

Every function of the C/C++ bindings returns an integer which describes an error code. Data returned from the device, when a getter is called, is handled via call by reference. These parameters are labeled with the `ret_` prefix.

Possible error codes are:

- E_OK = 0
- E_TIMEOUT = -1
- E_NO_STREAM_SOCKET = -2
- E_HOSTNAME_INVALID = -3
- E_NO_CONNECT = -4
- E_NO_THREAD = -5
- E_NOT_ADDED = -6 (unused since bindings version 2.0.0)
- E_ALREADY_CONNECTED = -7
- E_NOT_CONNECTED = -8
- E_INVALID_PARAMETER = -9
- E_NOT_SUPPORTED = -10
- E_UNKNOWN_ERROR_CODE = -11

as defined in `ip_connection.h`.

All functions listed below are thread-safe.

### Basic Functions

void `gas_detector_create`(GasDetector *gas_detector, const char *uid, IPConnection *ipcon)

  Creates the device object `gas_detector` with the unique device ID `uid` and adds it to the IPConnection `ipcon`:

      GasDetector gas_detector;
      gas_detector_create(&gas_detector, "YOUR_DEVICE_UID", &ipcon);

  This device object can be used after the IP connection has been connected (see examples above).

void `gas_detector_destroy`(GasDetector *gas_detector)

  Removes the device object `gas_detector` from its IPConnection and destroys it. The device object cannot be used anymore afterwards.

int `gas_detector_get_value`(GasDetector *gas_detector, uint16_t *ret_value)

  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 `GAS_DETECTOR_CALLBACK_VALUE` and set the period with `gas_detector_set_value_callback_period()`.

### Advanced Functions

int `gas_detector_set_moving_average`(GasDetector *gas_detector, uint8_t average)

  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.

int `gas_detector_get_moving_average`(GasDetector *gas_detector, uint8_t *ret_average)

  Returns the length moving average as set by `gas_detector_set_moving_average()`.

int `gas_detector_set_detector_type`(GasDetector *gas_detector, uint8_t detector_type)

  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 defines are available for this function:

  - GAS_DETECTOR_DETECTOR_TYPE_0 = 0
  - GAS_DETECTOR_DETECTOR_TYPE_1 = 1

int `gas_detector_get_detector_type`(GasDetector *gas_detector, uint8_t *ret_detector_type)

  Returns the detector type as set by `gas_detector_set_detector_type()`.

  The following defines are available for this function:

  - GAS_DETECTOR_DETECTOR_TYPE_0 = 0
  - GAS_DETECTOR_DETECTOR_TYPE_1 = 1

int `gas_detector_heater_on`(GasDetector *gas_detector)

  Turns the internal heater on.

int `gas_detector_heater_off`(GasDetector *gas_detector)

  Turns the internal heater off.

int `gas_detector_is_heater_on`(GasDetector *gas_detector, bool *ret_heater)

  Returns true if the heater is on, false otherwise.

int `gas_detector_get_api_version`(GasDetector *gas_detector, uint8_t ret_api_version[3])

  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.

int `gas_detector_get_response_expected`(GasDetector *gas_detector, uint8_t function_id, bool *ret_response_expected)

  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 `gas_detector_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 `gas_detector_set_response_expected()` for the list of function ID defines available for this function.

int `gas_detector_set_response_expected`(GasDetector *gas_detector, uint8_t 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 defines are available for this function:

  - GAS_DETECTOR_FUNCTION_SET_VALUE_CALLBACK_PERIOD = 2
  - GAS_DETECTOR_FUNCTION_SET_VALUE_CALLBACK_THRESHOLD = 4
  - GAS_DETECTOR_FUNCTION_SET_DEBOUNCE_PERIOD = 6
  - GAS_DETECTOR_FUNCTION_SET_MOVING_AVERAGE = 8
  - GAS_DETECTOR_FUNCTION_SET_DETECTOR_TYPE = 10
  - GAS_DETECTOR_FUNCTION_HEATER_ON = 12
  - GAS_DETECTOR_FUNCTION_HEATER_OFF = 13

int `gas_detector_set_response_expected_all`(GasDetector *gas_detector, bool response_expected)

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

int `gas_detector_get_identity`(GasDetector *gas_detector, char ret_uid[8], char ret_connected_uid[8], char *ret_position, uint8_t ret_hardware_version[3], uint8_t ret_firmware_version[3], uint16_t *ret_device_identifier)

  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.

### Callback Configuration Functions

void `gas_detector_register_callback`(GasDetector *gas_detector, uint8_t id, void *callback, void *user_data)

  Registers a callback with ID `id` to the function `callback`. The `user_data` will be given as a parameter of the callback.

  The available IDs with corresponding function signatures are listed below.

int `gas_detector_set_value_callback_period`(GasDetector *gas_detector, uint32_t period)

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

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

  The default value is 0.

int `gas_detector_get_value_callback_period`(GasDetector *gas_detector, uint32_t *ret_period)

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

int `gas_detector_set_value_callback_threshold`(GasDetector *gas_detector, char option, uint16_t min, uint16_t max)

  Sets the thresholds for the `GAS_DETECTOR_CALLBACK_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 defines are available for this function:

  - GAS_DETECTOR_THRESHOLD_OPTION_OFF = 'x'
  - GAS_DETECTOR_THRESHOLD_OPTION_OUTSIDE = 'o'
  - GAS_DETECTOR_THRESHOLD_OPTION_INSIDE = 'i'
  - GAS_DETECTOR_THRESHOLD_OPTION_SMALLER = '<'
  - GAS_DETECTOR_THRESHOLD_OPTION_GREATER = '>'

int `gas_detector_get_value_callback_threshold`(GasDetector *gas_detector, char *ret_option, uint16_t *ret_min, uint16_t *ret_max)

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

  The following defines are available for this function:

  - GAS_DETECTOR_THRESHOLD_OPTION_OFF = 'x'
  - GAS_DETECTOR_THRESHOLD_OPTION_OUTSIDE = 'o'
  - GAS_DETECTOR_THRESHOLD_OPTION_INSIDE = 'i'
  - GAS_DETECTOR_THRESHOLD_OPTION_SMALLER = '<'
  - GAS_DETECTOR_THRESHOLD_OPTION_GREATER = '>'

int `gas_detector_set_debounce_period`(GasDetector *gas_detector, uint32_t debounce)

  Sets the period in ms with which the threshold callback

  - `GAS_DETECTOR_CALLBACK_VALUE_REACHED`

  is triggered, if the threshold

  - `gas_detector_set_value_callback_threshold()`

  keeps being reached.

  The default value is 100.

int `gas_detector_get_debounce_period`(GasDetector *gas_detector, uint32_t *ret_debounce)

  Returns the debounce period as set by `gas_detector_set_debounce_period()`.

### Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the `gas_detector_register_callback()` function. The parameters consist of the device object, the callback ID, the callback function and optional user data:

>     void my_callback(int p, void *user_data) {
>         printf("parameter: %d\n", p);
>     }

>     gas_detector_register_callback(&gas_detector, GAS_DETECTOR_CALLBACK_EXAMPLE, (void *)my_callback, NULL);

The available constants with corresponding callback 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.

`GAS_DETECTOR_CALLBACK_VALUE`

      void callback(uint16_t value, void *user_data)

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

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

`GAS_DETECTOR_CALLBACK_VALUE_REACHED`

      void callback(uint16_t value, void *user_data)

  This callback is triggered when the threshold as set by `gas_detector_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 `gas_detector_set_debounce_period()`.

### Constants

`GAS_DETECTOR_DEVICE_IDENTIFIER`

  This constant is used to identify a Gas Detector Bricklet.

  The `gas_detector_get_identity()` function and the `IPCON_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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