Delphi/Lazarus - Accelerometer Bricklet

This is the description of the Delphi/Lazarus API bindings for the Accelerometer Bricklet. General information and technical specifications for the Accelerometer 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, BrickletAccelerometer;

type
  TExample = class
  private
    ipcon: TIPConnection;
    a: TBrickletAccelerometer;
  public
    procedure Execute;
  end;

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

var
  e: TExample;

procedure TExample.Execute;
var x, y, z: smallint;
begin
  { Create IP connection }
  ipcon := TIPConnection.Create;

  { Create device object }
  a := TBrickletAccelerometer.Create(UID, ipcon);

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

  { Get current acceleration }
  a.GetAcceleration(x, y, z);

  WriteLn(Format('Acceleration [X]: %f g', [x/1000.0]));
  WriteLn(Format('Acceleration [Y]: %f g', [y/1000.0]));
  WriteLn(Format('Acceleration [Z]: %f g', [z/1000.0]));

  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, BrickletAccelerometer;

type
  TExample = class
  private
    ipcon: TIPConnection;
    a: TBrickletAccelerometer;
  public
    procedure AccelerationCB(sender: TBrickletAccelerometer; const x: smallint;
                             const y: smallint; const z: smallint);
    procedure Execute;
  end;

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

var
  e: TExample;

{ Callback procedure for acceleration callback }
procedure TExample.AccelerationCB(sender: TBrickletAccelerometer; const x: smallint;
                                  const y: smallint; const z: smallint);
begin
  WriteLn(Format('Acceleration [X]: %f g', [x/1000.0]));
  WriteLn(Format('Acceleration [Y]: %f g', [y/1000.0]));
  WriteLn(Format('Acceleration [Z]: %f g', [z/1000.0]));
  WriteLn('');
end;

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

  { Create device object }
  a := TBrickletAccelerometer.Create(UID, ipcon);

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

  { Register acceleration callback to procedure AccelerationCB }
  a.OnAcceleration := {$ifdef FPC}@{$endif}AccelerationCB;

  { Set period for acceleration callback to 1s (1000ms)
    Note: The acceleration callback is only called every second
          if the acceleration has changed since the last call! }
  a.SetAccelerationCallbackPeriod(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, BrickletAccelerometer;

type
  TExample = class
  private
    ipcon: TIPConnection;
    a: TBrickletAccelerometer;
  public
    procedure AccelerationReachedCB(sender: TBrickletAccelerometer; const x: smallint;
                                    const y: smallint; const z: smallint);
    procedure Execute;
  end;

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

var
  e: TExample;

{ Callback procedure for acceleration reached callback }
procedure TExample.AccelerationReachedCB(sender: TBrickletAccelerometer;
                                         const x: smallint; const y: smallint;
                                         const z: smallint);
begin
  WriteLn(Format('Acceleration [X]: %f g', [x/1000.0]));
  WriteLn(Format('Acceleration [Y]: %f g', [y/1000.0]));
  WriteLn(Format('Acceleration [Z]: %f g', [z/1000.0]));
  WriteLn('');
end;

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

  { Create device object }
  a := TBrickletAccelerometer.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) }
  a.SetDebouncePeriod(10000);

  { Register acceleration reached callback to procedure AccelerationReachedCB }
  a.OnAccelerationReached := {$ifdef FPC}@{$endif}AccelerationReachedCB;

  { Configure threshold for acceleration "greater than 2 g, 2 g, 2 g" }
  a.SetAccelerationCallbackThreshold('>', 2*1000, 0, 2*1000, 0, 2*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 TBrickletAccelerometer.Create(const uid: string; ipcon: TIPConnection)

Creates an object with the unique device ID uid:

accelerometer := TBrickletAccelerometer.Create('YOUR_DEVICE_UID', ipcon);

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

procedure TBrickletAccelerometer.GetAcceleration(out x: smallint; out y: smallint; out z: smallint)

Returns the acceleration in x, y and z direction. The values are given in g/1000 (1g = 9.80665m/s²), not to be confused with grams.

If you want to get the acceleration periodically, it is recommended to use the OnAcceleration callback and set the period with SetAccelerationCallbackPeriod.

function TBrickletAccelerometer.GetTemperature: smallint

Returns the temperature of the accelerometer in °C.

procedure TBrickletAccelerometer.LEDOn

Enables the LED on the Bricklet.

procedure TBrickletAccelerometer.LEDOff

Disables the LED on the Bricklet.

function TBrickletAccelerometer.IsLEDOn: boolean

Returns true if the LED is enabled, false otherwise.

Advanced Functions

procedure TBrickletAccelerometer.SetConfiguration(const dataRate: byte; const fullScale: byte; const filterBandwidth: byte)

Configures the data rate, full scale range and filter bandwidth. Possible values are:

  • Data rate of 0Hz to 1600Hz.
  • Full scale range of -2G to +2G up to -16G to +16G.
  • Filter bandwidth between 50Hz and 800Hz.

Decreasing data rate or full scale range will also decrease the noise on the data.

The default values are 100Hz data rate, -4G to +4G range and 200Hz filter bandwidth.

The following constants are available for this function:

  • BRICKLET_ACCELEROMETER_DATA_RATE_OFF = 0
  • BRICKLET_ACCELEROMETER_DATA_RATE_3HZ = 1
  • BRICKLET_ACCELEROMETER_DATA_RATE_6HZ = 2
  • BRICKLET_ACCELEROMETER_DATA_RATE_12HZ = 3
  • BRICKLET_ACCELEROMETER_DATA_RATE_25HZ = 4
  • BRICKLET_ACCELEROMETER_DATA_RATE_50HZ = 5
  • BRICKLET_ACCELEROMETER_DATA_RATE_100HZ = 6
  • BRICKLET_ACCELEROMETER_DATA_RATE_400HZ = 7
  • BRICKLET_ACCELEROMETER_DATA_RATE_800HZ = 8
  • BRICKLET_ACCELEROMETER_DATA_RATE_1600HZ = 9
  • BRICKLET_ACCELEROMETER_FULL_SCALE_2G = 0
  • BRICKLET_ACCELEROMETER_FULL_SCALE_4G = 1
  • BRICKLET_ACCELEROMETER_FULL_SCALE_6G = 2
  • BRICKLET_ACCELEROMETER_FULL_SCALE_8G = 3
  • BRICKLET_ACCELEROMETER_FULL_SCALE_16G = 4
  • BRICKLET_ACCELEROMETER_FILTER_BANDWIDTH_800HZ = 0
  • BRICKLET_ACCELEROMETER_FILTER_BANDWIDTH_400HZ = 1
  • BRICKLET_ACCELEROMETER_FILTER_BANDWIDTH_200HZ = 2
  • BRICKLET_ACCELEROMETER_FILTER_BANDWIDTH_50HZ = 3
procedure TBrickletAccelerometer.GetConfiguration(out dataRate: byte; out fullScale: byte; out filterBandwidth: byte)

Returns the configuration as set by SetConfiguration.

The following constants are available for this function:

  • BRICKLET_ACCELEROMETER_DATA_RATE_OFF = 0
  • BRICKLET_ACCELEROMETER_DATA_RATE_3HZ = 1
  • BRICKLET_ACCELEROMETER_DATA_RATE_6HZ = 2
  • BRICKLET_ACCELEROMETER_DATA_RATE_12HZ = 3
  • BRICKLET_ACCELEROMETER_DATA_RATE_25HZ = 4
  • BRICKLET_ACCELEROMETER_DATA_RATE_50HZ = 5
  • BRICKLET_ACCELEROMETER_DATA_RATE_100HZ = 6
  • BRICKLET_ACCELEROMETER_DATA_RATE_400HZ = 7
  • BRICKLET_ACCELEROMETER_DATA_RATE_800HZ = 8
  • BRICKLET_ACCELEROMETER_DATA_RATE_1600HZ = 9
  • BRICKLET_ACCELEROMETER_FULL_SCALE_2G = 0
  • BRICKLET_ACCELEROMETER_FULL_SCALE_4G = 1
  • BRICKLET_ACCELEROMETER_FULL_SCALE_6G = 2
  • BRICKLET_ACCELEROMETER_FULL_SCALE_8G = 3
  • BRICKLET_ACCELEROMETER_FULL_SCALE_16G = 4
  • BRICKLET_ACCELEROMETER_FILTER_BANDWIDTH_800HZ = 0
  • BRICKLET_ACCELEROMETER_FILTER_BANDWIDTH_400HZ = 1
  • BRICKLET_ACCELEROMETER_FILTER_BANDWIDTH_200HZ = 2
  • BRICKLET_ACCELEROMETER_FILTER_BANDWIDTH_50HZ = 3
function TBrickletAccelerometer.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 TBrickletAccelerometer.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 TBrickletAccelerometer.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_ACCELEROMETER_FUNCTION_SET_ACCELERATION_CALLBACK_PERIOD = 2
  • BRICKLET_ACCELEROMETER_FUNCTION_SET_ACCELERATION_CALLBACK_THRESHOLD = 4
  • BRICKLET_ACCELEROMETER_FUNCTION_SET_DEBOUNCE_PERIOD = 6
  • BRICKLET_ACCELEROMETER_FUNCTION_SET_CONFIGURATION = 9
  • BRICKLET_ACCELEROMETER_FUNCTION_LED_ON = 11
  • BRICKLET_ACCELEROMETER_FUNCTION_LED_OFF = 12
procedure TBrickletAccelerometer.SetResponseExpectedAll(const responseExpected: boolean)

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

procedure TBrickletAccelerometer.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 TBrickletAccelerometer.SetAccelerationCallbackPeriod(const period: longword)

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

The OnAcceleration callback is only triggered if the acceleration has changed since the last triggering.

The default value is 0.

function TBrickletAccelerometer.GetAccelerationCallbackPeriod: longword

Returns the period as set by SetAccelerationCallbackPeriod.

procedure TBrickletAccelerometer.SetAccelerationCallbackThreshold(const option: char; const minX: smallint; const maxX: smallint; const minY: smallint; const maxY: smallint; const minZ: smallint; const maxZ: smallint)

Sets the thresholds for the OnAccelerationReached callback.

The following options are possible:

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

The default value is ('x', 0, 0, 0, 0, 0, 0).

The following constants are available for this function:

  • BRICKLET_ACCELEROMETER_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_ACCELEROMETER_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_ACCELEROMETER_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_ACCELEROMETER_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_ACCELEROMETER_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletAccelerometer.GetAccelerationCallbackThreshold(out option: char; out minX: smallint; out maxX: smallint; out minY: smallint; out maxY: smallint; out minZ: smallint; out maxZ: smallint)

Returns the threshold as set by SetAccelerationCallbackThreshold.

The following constants are available for this function:

  • BRICKLET_ACCELEROMETER_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_ACCELEROMETER_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_ACCELEROMETER_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_ACCELEROMETER_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_ACCELEROMETER_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletAccelerometer.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 TBrickletAccelerometer.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: TBrickletAccelerometer; const param: word);
begin
  WriteLn(param);
end;

accelerometer.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 TBrickletAccelerometer.OnAcceleration
procedure(sender: TBrickletAccelerometer; const x: smallint; const y: smallint; const z: smallint) of object;

This callback is triggered periodically with the period that is set by SetAccelerationCallbackPeriod. The parameters are the X, Y and Z acceleration.

The OnAcceleration callback is only triggered if the acceleration has changed since the last triggering.

property TBrickletAccelerometer.OnAccelerationReached
procedure(sender: TBrickletAccelerometer; const x: smallint; const y: smallint; const z: smallint) of object;

This callback is triggered when the threshold as set by SetAccelerationCallbackThreshold is reached. The parameters are the X, Y and Z acceleration.

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

Constants

const BRICKLET_ACCELEROMETER_DEVICE_IDENTIFIER

This constant is used to identify a Accelerometer 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_ACCELEROMETER_DEVICE_DISPLAY_NAME

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