Delphi/Lazarus - Barometer Bricklet

This is the description of the Delphi/Lazarus API bindings for the Barometer Bricklet. General information and technical specifications for the Barometer 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).

Simple

Download (ExampleSimple.pas)

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program ExampleSimple;

{$ifdef MSWINDOWS}{$apptype CONSOLE}{$endif}
{$ifdef FPC}{$mode OBJFPC}{$H+}{$endif}

uses
  SysUtils, IPConnection, BrickletBarometer;

type
  TExample = class
  private
    ipcon: TIPConnection;
    b: TBrickletBarometer;
  public
    procedure Execute;
  end;

const
  HOST = 'localhost';
  PORT = 4223;
  UID = 'XYZ'; { Change XYZ to the UID of your Barometer Bricklet }

var
  e: TExample;

procedure TExample.Execute;
var airPressure, altitude: longint;
begin
  { Create IP connection }
  ipcon := TIPConnection.Create;

  { Create device object }
  b := TBrickletBarometer.Create(UID, ipcon);

  { Connect to brickd }
  ipcon.Connect(HOST, PORT);
  { Don't use device before ipcon is connected }

  { Get current air pressure }
  airPressure := b.GetAirPressure;
  WriteLn(Format('Air Pressure: %f mbar', [airPressure/1000.0]));

  { Get current altitude }
  altitude := b.GetAltitude;
  WriteLn(Format('Altitude: %f m', [altitude/100.0]));

  WriteLn('Press key to exit');
  ReadLn;
  ipcon.Destroy; { Calls ipcon.Disconnect internally }
end;

begin
  e := TExample.Create;
  e.Execute;
  e.Destroy;
end.

Callback

Download (ExampleCallback.pas)

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program ExampleCallback;

{$ifdef MSWINDOWS}{$apptype CONSOLE}{$endif}
{$ifdef FPC}{$mode OBJFPC}{$H+}{$endif}

uses
  SysUtils, IPConnection, BrickletBarometer;

type
  TExample = class
  private
    ipcon: TIPConnection;
    b: TBrickletBarometer;
  public
    procedure AirPressureCB(sender: TBrickletBarometer; const airPressure: longint);
    procedure Execute;
  end;

const
  HOST = 'localhost';
  PORT = 4223;
  UID = 'XYZ'; { Change XYZ to the UID of your Barometer Bricklet }

var
  e: TExample;

{ Callback procedure for air pressure callback }
procedure TExample.AirPressureCB(sender: TBrickletBarometer; const airPressure: longint);
begin
  WriteLn(Format('Air Pressure: %f mbar', [airPressure/1000.0]));
end;

procedure TExample.Execute;
begin
  { Create IP connection }
  ipcon := TIPConnection.Create;

  { Create device object }
  b := TBrickletBarometer.Create(UID, ipcon);

  { Connect to brickd }
  ipcon.Connect(HOST, PORT);
  { Don't use device before ipcon is connected }

  { Register air pressure callback to procedure AirPressureCB }
  b.OnAirPressure := {$ifdef FPC}@{$endif}AirPressureCB;

  { Set period for air pressure callback to 1s (1000ms)
    Note: The air pressure callback is only called every second
          if the air pressure has changed since the last call! }
  b.SetAirPressureCallbackPeriod(1000);

  WriteLn('Press key to exit');
  ReadLn;
  ipcon.Destroy; { Calls ipcon.Disconnect internally }
end;

begin
  e := TExample.Create;
  e.Execute;
  e.Destroy;
end.

Threshold

Download (ExampleThreshold.pas)

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program ExampleThreshold;

{$ifdef MSWINDOWS}{$apptype CONSOLE}{$endif}
{$ifdef FPC}{$mode OBJFPC}{$H+}{$endif}

uses
  SysUtils, IPConnection, BrickletBarometer;

type
  TExample = class
  private
    ipcon: TIPConnection;
    b: TBrickletBarometer;
  public
    procedure AirPressureReachedCB(sender: TBrickletBarometer;
                                   const airPressure: longint);
    procedure Execute;
  end;

const
  HOST = 'localhost';
  PORT = 4223;
  UID = 'XYZ'; { Change XYZ to the UID of your Barometer Bricklet }

var
  e: TExample;

{ Callback procedure for air pressure reached callback }
procedure TExample.AirPressureReachedCB(sender: TBrickletBarometer;
                                        const airPressure: longint);
begin
  WriteLn(Format('Air Pressure: %f mbar', [airPressure/1000.0]));
  WriteLn('Enjoy the potentially good weather!');
end;

procedure TExample.Execute;
begin
  { Create IP connection }
  ipcon := TIPConnection.Create;

  { Create device object }
  b := TBrickletBarometer.Create(UID, ipcon);

  { Connect to brickd }
  ipcon.Connect(HOST, PORT);
  { Don't use device before ipcon is connected }

  { Get threshold callbacks with a debounce time of 10 seconds (10000ms) }
  b.SetDebouncePeriod(10000);

  { Register air pressure reached callback to procedure AirPressureReachedCB }
  b.OnAirPressureReached := {$ifdef FPC}@{$endif}AirPressureReachedCB;

  { Configure threshold for air pressure "greater than 1025 mbar" }
  b.SetAirPressureCallbackThreshold('>', 1025*1000, 0);

  WriteLn('Press key to exit');
  ReadLn;
  ipcon.Destroy; { Calls ipcon.Disconnect internally }
end;

begin
  e := TExample.Create;
  e.Execute;
  e.Destroy;
end.

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 TBrickletBarometer.Create(const uid: string; ipcon: TIPConnection)

Creates an object with the unique device ID uid:

barometer := TBrickletBarometer.Create('YOUR_DEVICE_UID', ipcon);

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

function TBrickletBarometer.GetAirPressure: longint

Returns the air pressure of the air pressure sensor. The value has a range of 10000 to 1200000 and is given in mbar/1000, i.e. a value of 1001092 means that an air pressure of 1001.092 mbar is measured.

If you want to get the air pressure periodically, it is recommended to use the OnAirPressure callback and set the period with SetAirPressureCallbackPeriod.

function TBrickletBarometer.GetAltitude: longint

Returns the relative altitude of the air pressure sensor. The value is given in cm and is calculated based on the difference between the current air pressure and the reference air pressure that can be set with SetReferenceAirPressure.

If you want to get the altitude periodically, it is recommended to use the OnAltitude callback and set the period with SetAltitudeCallbackPeriod.

procedure TBrickletBarometer.SetReferenceAirPressure(const airPressure: longint)

Sets the reference air pressure in mbar/1000 for the altitude calculation. Valid values are between 10000 and 1200000. Setting the reference to the current air pressure results in a calculated altitude of 0cm. Passing 0 is a shortcut for passing the current air pressure as reference.

Well known reference values are the Q codes QNH and QFE used in aviation.

The default value is 1013.25mbar.

function TBrickletBarometer.GetReferenceAirPressure: longint

Returns the reference air pressure as set by SetReferenceAirPressure.

Advanced Functions

function TBrickletBarometer.GetChipTemperature: smallint

Returns the temperature of the air pressure sensor. The value has a range of -4000 to 8500 and is given in °C/100, i.e. a value of 2007 means that a temperature of 20.07 °C is measured.

This temperature is used internally for temperature compensation of the air pressure measurement. It is not as accurate as the temperature measured by the Temperature Bricklet or the Temperature IR Bricklet.

procedure TBrickletBarometer.SetAveraging(const movingAveragePressure: byte; const averagePressure: byte; const averageTemperature: byte)

Sets the different averaging parameters. It is possible to set the length of a normal averaging for the temperature and pressure, as well as an additional length of a moving average for the pressure. The moving average is calculated from the normal averages. There is no moving average for the temperature.

The maximum length for the pressure average is 10, for the temperature average is 255 and for the moving average is 25.

Setting the all three parameters to 0 will turn the averaging completely off. If the averaging is off, there is lots of noise on the data, but the data is without delay. Thus we recommend to turn the averaging off if the Barometer Bricklet data is to be used for sensor fusion with other sensors.

The default values are 10 for the normal averages and 25 for the moving average.

New in version 2.0.1 (Plugin).

procedure TBrickletBarometer.GetAveraging(out movingAveragePressure: byte; out averagePressure: byte; out averageTemperature: byte)

Returns the averaging configuration as set by SetAveraging.

New in version 2.0.1 (Plugin).

function TBrickletBarometer.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 TBrickletBarometer.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 TBrickletBarometer.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.

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_BAROMETER_FUNCTION_SET_AIR_PRESSURE_CALLBACK_PERIOD = 3
  • BRICKLET_BAROMETER_FUNCTION_SET_ALTITUDE_CALLBACK_PERIOD = 5
  • BRICKLET_BAROMETER_FUNCTION_SET_AIR_PRESSURE_CALLBACK_THRESHOLD = 7
  • BRICKLET_BAROMETER_FUNCTION_SET_ALTITUDE_CALLBACK_THRESHOLD = 9
  • BRICKLET_BAROMETER_FUNCTION_SET_DEBOUNCE_PERIOD = 11
  • BRICKLET_BAROMETER_FUNCTION_SET_REFERENCE_AIR_PRESSURE = 13
  • BRICKLET_BAROMETER_FUNCTION_SET_AVERAGING = 20
procedure TBrickletBarometer.SetResponseExpectedAll(const responseExpected: boolean)

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

procedure TBrickletBarometer.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 TBrickletBarometer.SetAirPressureCallbackPeriod(const period: longword)

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

The OnAirPressure callback is only triggered if the air pressure has changed since the last triggering.

The default value is 0.

function TBrickletBarometer.GetAirPressureCallbackPeriod: longword

Returns the period as set by SetAirPressureCallbackPeriod.

procedure TBrickletBarometer.SetAltitudeCallbackPeriod(const period: longword)

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

The OnAltitude callback is only triggered if the altitude has changed since the last triggering.

The default value is 0.

function TBrickletBarometer.GetAltitudeCallbackPeriod: longword

Returns the period as set by SetAltitudeCallbackPeriod.

procedure TBrickletBarometer.SetAirPressureCallbackThreshold(const option: char; const min: longint; const max: longint)

Sets the thresholds for the OnAirPressureReached callback.

The following options are possible:

Option Description
'x' Callback is turned off
'o' Callback is triggered when the air pressure is outside the min and max values
'i' Callback is triggered when the air pressure is inside the min and max values
'<' Callback is triggered when the air pressure is smaller than the min value (max is ignored)
'>' Callback is triggered when the air pressure 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_BAROMETER_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_BAROMETER_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_BAROMETER_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_BAROMETER_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_BAROMETER_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletBarometer.GetAirPressureCallbackThreshold(out option: char; out min: longint; out max: longint)

Returns the threshold as set by SetAirPressureCallbackThreshold.

The following constants are available for this function:

  • BRICKLET_BAROMETER_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_BAROMETER_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_BAROMETER_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_BAROMETER_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_BAROMETER_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletBarometer.SetAltitudeCallbackThreshold(const option: char; const min: longint; const max: longint)

Sets the thresholds for the OnAltitudeReached callback.

The following options are possible:

Option Description
'x' Callback is turned off
'o' Callback is triggered when the altitude is outside the min and max values
'i' Callback is triggered when the altitude is inside the min and max values
'<' Callback is triggered when the altitude is smaller than the min value (max is ignored)
'>' Callback is triggered when the altitude 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_BAROMETER_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_BAROMETER_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_BAROMETER_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_BAROMETER_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_BAROMETER_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletBarometer.GetAltitudeCallbackThreshold(out option: char; out min: longint; out max: longint)

Returns the threshold as set by SetAltitudeCallbackThreshold.

The following constants are available for this function:

  • BRICKLET_BAROMETER_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_BAROMETER_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_BAROMETER_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_BAROMETER_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_BAROMETER_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletBarometer.SetDebouncePeriod(const debounce: longword)

Sets the period in ms with which the threshold callbacks

are triggered, if the thresholds

keep being reached.

The default value is 100.

function TBrickletBarometer.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: TBrickletBarometer; const param: word);
begin
  WriteLn(param);
end;

barometer.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 TBrickletBarometer.OnAirPressure
procedure(sender: TBrickletBarometer; const airPressure: longint) of object;

This callback is triggered periodically with the period that is set by SetAirPressureCallbackPeriod. The parameter is the air pressure of the air pressure sensor.

The OnAirPressure callback is only triggered if the air pressure has changed since the last triggering.

property TBrickletBarometer.OnAltitude
procedure(sender: TBrickletBarometer; const altitude: longint) of object;

This callback is triggered periodically with the period that is set by SetAltitudeCallbackPeriod. The parameter is the altitude of the air pressure sensor.

The OnAltitude callback is only triggered if the altitude has changed since the last triggering.

property TBrickletBarometer.OnAirPressureReached
procedure(sender: TBrickletBarometer; const airPressure: longint) of object;

This callback is triggered when the threshold as set by SetAirPressureCallbackThreshold is reached. The parameter is the air pressure of the air pressure sensor.

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

property TBrickletBarometer.OnAltitudeReached
procedure(sender: TBrickletBarometer; const altitude: longint) of object;

This callback is triggered when the threshold as set by SetAltitudeCallbackThreshold is reached. The parameter is the altitude of the air pressure sensor.

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

Constants

const BRICKLET_BAROMETER_DEVICE_IDENTIFIER

This constant is used to identify a Barometer 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.

const BRICKLET_BAROMETER_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Barometer Bricklet.