Delphi/Lazarus - Piezo Speaker Bricklet

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

Beep

Download (ExampleBeep.pas)

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program ExampleBeep;

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

uses
  SysUtils, IPConnection, BrickletPiezoSpeaker;

type
  TExample = class
  private
    ipcon: TIPConnection;
    ps: TBrickletPiezoSpeaker;
  public
    procedure Execute;
  end;

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

var
  e: TExample;

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

  { Create device object }
  ps := TBrickletPiezoSpeaker.Create(UID, ipcon);

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

  { Make 2 second beep with a frequency of 1kHz }
  ps.Beep(2000, 1000);

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

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

Morse Code

Download (ExampleMorseCode.pas)

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program ExampleMorseCode;

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

uses
  SysUtils, IPConnection, BrickletPiezoSpeaker;

type
  TExample = class
  private
    ipcon: TIPConnection;
    ps: TBrickletPiezoSpeaker;
  public
    procedure Execute;
  end;

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

var
  e: TExample;

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

  { Create device object }
  ps := TBrickletPiezoSpeaker.Create(UID, ipcon);

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

  { Morse SOS with a frequency of 2kHz }
  ps.MorseCode('... --- ...', 2000);

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

Creates an object with the unique device ID uid:

piezoSpeaker := TBrickletPiezoSpeaker.Create('YOUR_DEVICE_UID', ipcon);

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

procedure TBrickletPiezoSpeaker.Beep(const duration: longword; const frequency: word)

Beeps with the given frequency for the duration in ms. For example: If you set a duration of 1000, with a frequency value of 2000 the piezo buzzer will beep for one second with a frequency of approximately 2 kHz.

Changed in version 2.0.2 (Plugin): A duration of 0 stops the current beep if any, the frequency parameter is ignored. A duration of 4294967295 results in an infinite beep.

The frequency parameter can be set between 585 and 7100.

The Piezo Speaker Bricklet can only approximate the frequency, it will play the best possible match by applying the calibration (see Calibrate).

The following constants are available for this function:

  • BRICKLET_PIEZO_SPEAKER_BEEP_DURATION_OFF = 0
  • BRICKLET_PIEZO_SPEAKER_BEEP_DURATION_INFINITE = 4294967295
procedure TBrickletPiezoSpeaker.MorseCode(const morse: string; const frequency: word)

Sets morse code that will be played by the piezo buzzer. The morse code is given as a string consisting of "." (dot), "-" (minus) and " " (space) for dits, dahs and pauses. Every other character is ignored. The second parameter is the frequency (see Beep).

For example: If you set the string "...---...", the piezo buzzer will beep nine times with the durations "short short short long long long short short short".

The maximum string size is 60.

Advanced Functions

function TBrickletPiezoSpeaker.Calibrate: boolean

The Piezo Speaker Bricklet can play 512 different tones. This function plays each tone and measures the exact frequency back. The result is a mapping between setting value and frequency. This mapping is stored in the EEPROM and loaded on startup.

The Bricklet should come calibrated, you only need to call this function (once) every time you reflash the Bricklet plugin.

Returns true after the calibration finishes.

function TBrickletPiezoSpeaker.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 TBrickletPiezoSpeaker.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 TBrickletPiezoSpeaker.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_PIEZO_SPEAKER_FUNCTION_BEEP = 1
  • BRICKLET_PIEZO_SPEAKER_FUNCTION_MORSE_CODE = 2
procedure TBrickletPiezoSpeaker.SetResponseExpectedAll(const responseExpected: boolean)

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

procedure TBrickletPiezoSpeaker.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

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: TBrickletPiezoSpeaker; const param: word);
begin
  WriteLn(param);
end;

piezoSpeaker.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 TBrickletPiezoSpeaker.OnBeepFinished
procedure(sender: TBrickletPiezoSpeaker) of object;

This callback is triggered if a beep set by Beep is finished

property TBrickletPiezoSpeaker.OnMorseCodeFinished
procedure(sender: TBrickletPiezoSpeaker) of object;

This callback is triggered if the playback of the morse code set by MorseCode is finished.

Constants

const BRICKLET_PIEZO_SPEAKER_DEVICE_IDENTIFIER

This constant is used to identify a Piezo Speaker 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_PIEZO_SPEAKER_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Piezo Speaker Bricklet.