Delphi/Lazarus - 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 Delphi/Lazarus 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 Delphi/Lazarus API bindings is part of their general description.

Examples

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

API

Since Delphi does not support multiple return values directly, we use the out keyword to return multiple values from a function.

All functions and procedures listed below are thread-safe.

Basic Functions

constructor TBrickletGasDetector.Create(const uid: string; ipcon: TIPConnection)

Creates an object with the unique device ID uid:

gasDetector := TBrickletGasDetector.Create('YOUR_DEVICE_UID', ipcon);

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

function TBrickletGasDetector.GetValue: word

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 OnValue and set the period with SetValueCallbackPeriod.

Advanced Functions

procedure TBrickletGasDetector.SetMovingAverage(const average: byte)

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.

function TBrickletGasDetector.GetMovingAverage: byte

Returns the length moving average as set by SetMovingAverage.

procedure TBrickletGasDetector.SetDetectorType(const detectorType: byte)

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 constants are available for this function:

  • BRICKLET_GAS_DETECTOR_DETECTOR_TYPE_0 = 0
  • BRICKLET_GAS_DETECTOR_DETECTOR_TYPE_1 = 1
function TBrickletGasDetector.GetDetectorType: byte

Returns the detector type as set by SetDetectorType.

The following constants are available for this function:

  • BRICKLET_GAS_DETECTOR_DETECTOR_TYPE_0 = 0
  • BRICKLET_GAS_DETECTOR_DETECTOR_TYPE_1 = 1
procedure TBrickletGasDetector.HeaterOn

Turns the internal heater on.

procedure TBrickletGasDetector.HeaterOff

Turns the internal heater off.

function TBrickletGasDetector.IsHeaterOn: boolean

Returns true if the heater is on, false otherwise.

function TBrickletGasDetector.GetAPIVersion: array [0..2] of byte

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.

function TBrickletGasDetector.GetResponseExpected(const functionId: byte): boolean

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 SetResponseExpected. 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 SetResponseExpected for the list of function ID constants available for this function.

procedure TBrickletGasDetector.SetResponseExpected(const functionId: byte; const responseExpected: boolean)

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:

  • BRICKLET_GAS_DETECTOR_FUNCTION_SET_VALUE_CALLBACK_PERIOD = 2
  • BRICKLET_GAS_DETECTOR_FUNCTION_SET_VALUE_CALLBACK_THRESHOLD = 4
  • BRICKLET_GAS_DETECTOR_FUNCTION_SET_DEBOUNCE_PERIOD = 6
  • BRICKLET_GAS_DETECTOR_FUNCTION_SET_MOVING_AVERAGE = 8
  • BRICKLET_GAS_DETECTOR_FUNCTION_SET_DETECTOR_TYPE = 10
  • BRICKLET_GAS_DETECTOR_FUNCTION_HEATER_ON = 12
  • BRICKLET_GAS_DETECTOR_FUNCTION_HEATER_OFF = 13
procedure TBrickletGasDetector.SetResponseExpectedAll(const responseExpected: boolean)

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

procedure TBrickletGasDetector.GetIdentity(out uid: string; out connectedUid: string; out position: char; out hardwareVersion: array [0..2] of byte; out firmwareVersion: array [0..2] of byte; out deviceIdentifier: word)

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

procedure TBrickletGasDetector.SetValueCallbackPeriod(const period: longword)

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

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

The default value is 0.

function TBrickletGasDetector.GetValueCallbackPeriod: longword

Returns the period as set by SetValueCallbackPeriod.

procedure TBrickletGasDetector.SetValueCallbackThreshold(const option: char; const min: word; const max: word)

Sets the thresholds for the OnValueReached 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 constants are available for this function:

  • BRICKLET_GAS_DETECTOR_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_GAS_DETECTOR_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_GAS_DETECTOR_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_GAS_DETECTOR_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_GAS_DETECTOR_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletGasDetector.GetValueCallbackThreshold(out option: char; out min: word; out max: word)

Returns the threshold as set by SetValueCallbackThreshold.

The following constants are available for this function:

  • BRICKLET_GAS_DETECTOR_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_GAS_DETECTOR_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_GAS_DETECTOR_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_GAS_DETECTOR_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_GAS_DETECTOR_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletGasDetector.SetDebouncePeriod(const debounce: longword)

Sets the period in ms with which the threshold callback

is triggered, if the threshold

keeps being reached.

The default value is 100.

function TBrickletGasDetector.GetDebouncePeriod: longword

Returns the debounce period as set by SetDebouncePeriod.

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done by assigning a procedure to an callback property of the device object:

procedure TExample.MyCallback(sender: TBrickletGasDetector; const param: word);
begin
  WriteLn(param);
end;

gasDetector.OnExample := {$ifdef FPC}@{$endif}example.MyCallback;

The available callback property and their 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.

property TBrickletGasDetector.OnValue
procedure(sender: TBrickletGasDetector; const value: word) of object;

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

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

property TBrickletGasDetector.OnValueReached
procedure(sender: TBrickletGasDetector; const value: word) of object;

This callback is triggered when the threshold as set by SetValueCallbackThreshold 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 SetDebouncePeriod.

Constants

const BRICKLET_GAS_DETECTOR_DEVICE_IDENTIFIER

This constant is used to identify a Gas Detector Bricklet.

The GetIdentity function and the OnEnumerate callback of the IP Connection have a deviceIdentifier parameter to specify the Brick's or Bricklet's type.

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