Delphi/Lazarus - Heart Rate 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 Heart Rate Bricklet. General information and technical specifications for the Heart Rate 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 Example;

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

uses
  SysUtils, IPConnection, BrickletHeartRate;

type
  TExample = class
  private
    ipcon: TIPConnection;
    hr: TBrickletHeartRate;
  public
    procedure Execute;
  end;

const
  HOST = 'localhost';
  PORT = 4223;
  UID = 'abc'; { Change to your UID }

var
  e: TExample;

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

  { Create device object }
  hr := TBrickletHeartRate.Create(UID, ipcon);

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

  { Get current heart rate (in beats per minute) }
  hrate := hr.GetHeartRate;
  WriteLn(Format('Heart Rate: %d bpm', [hrate]));

  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 Example;

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

uses
  SysUtils, IPConnection, BrickletHeartRate;

type
  TExample = class
  private
    ipcon: TIPConnection;
    hr: TBrickletHeartRate;
  public
    procedure HeartRateCB(sender: TBrickletHeartRate;
                      const hrate: Word);
    procedure Execute;
  end;

const
  HOST = 'localhost';
  PORT = 4223;
  UID = 'abc'; { Change to your UID }

var
  e: TExample;

{ Callback function for heart rate callback }
procedure TExample.HeartRateCB(sender: TBrickletHeartRate;
                           const hrate: Word);
begin
    WriteLn(Format('Heart Rate(bpm): %u', [hrate]));
    WriteLn('');
end;

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

  { Create device object }
  hr := TBrickletHeartRate.Create(UID, ipcon);

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

  { Set Period for heart rate callback to 1s (1000ms)
    Note: The callback is only called every second if the
          heart has changed since the last call! }
  hr.SetHeartRateCallbackPeriod(1000);

  { Register heart callback to procedure HeartRateCB }
  hr.OnHeartRate := {$ifdef FPC}@{$endif}HeartRateCB;

  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 Example;

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

uses
  SysUtils, IPConnection, BrickletHeartRate;

type
  TExample = class
  private
    ipcon: TIPConnection;
    hr: TBrickletHeartRate;
  public
    procedure ReachedCB(sender: TBrickletHeartRate; const hrate: Word);
    procedure Execute;
  end;

const
  HOST = 'localhost';
  PORT = 4223;
  UID = 'abc'; { Change to your UID }

var
  e: TExample;

{ Callback for color threshold reached }
procedure TExample.ReachedCB(sender: TBrickletHeartRate; const hrate: word);
begin
    WriteLn(Format('Heart Rate(bpm): %u', [hrate]));
    WriteLn('');
end;

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

  { Create device object }
  hr := TBrickletHeartRate.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) }
  hr.SetDebouncePeriod(10000);

  { Register threshold reached callback to procedure ReachedCB }
  hr.OnHeartRateReached := {$ifdef FPC}@{$endif}ReachedCB;

  { Configure threshold for heart rate values,
    Heart Rate  : greater than 70 beats per minute }
  hr.SetHeartRateCallbackThreshold('>', 50, 70);

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

Creates an object with the unique device ID uid:

heartRate := TBrickletHeartRate.Create('YOUR_DEVICE_UID', ipcon);

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

function TBrickletHeartRate.GetHeartRate: word

Returns the current heart rate measured.

If you want to get the heart rate periodically, it is recommended to use the callback OnHeartRate and set the period with SetHeartRateCallbackPeriod.

Advanced Functions

function TBrickletHeartRate.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 TBrickletHeartRate.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 TBrickletHeartRate.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_HEART_RATE_FUNCTION_SET_HEART_RATE_CALLBACK_PERIOD = 2
  • BRICKLET_HEART_RATE_FUNCTION_SET_HEART_RATE_CALLBACK_THRESHOLD = 4
  • BRICKLET_HEART_RATE_FUNCTION_SET_DEBOUNCE_PERIOD = 6
  • BRICKLET_HEART_RATE_FUNCTION_ENABLE_BEAT_STATE_CHANGED_CALLBACK = 11
  • BRICKLET_HEART_RATE_FUNCTION_DISABLE_BEAT_STATE_CHANGED_CALLBACK = 12
procedure TBrickletHeartRate.SetResponseExpectedAll(const responseExpected: boolean)

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

procedure TBrickletHeartRate.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 TBrickletHeartRate.SetHeartRateCallbackPeriod(const period: longword)

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

OnHeartRate is only triggered if the heart rate has changed since the last triggering.

The default value is 0.

function TBrickletHeartRate.GetHeartRateCallbackPeriod: longword

Returns the period as set by SetHeartRateCallbackPeriod.

procedure TBrickletHeartRate.SetHeartRateCallbackThreshold(const option: char; const min: word; const max: word)

Sets the thresholds for the OnHeartRateReached callback.

The following options are possible:

Option Description
'x' Callback is turned off
'o' Callback is triggered when the heart rate is outside the min and max values
'i' Callback is triggered when the heart rate is inside the min and max values
'<' Callback is triggered when the heart rate is smaller than the min value (max is ignored)
'>' Callback is triggered when the heart rate 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_HEART_RATE_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_HEART_RATE_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_HEART_RATE_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_HEART_RATE_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_HEART_RATE_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletHeartRate.GetHeartRateCallbackThreshold(out option: char; out min: word; out max: word)

Returns the threshold as set by SetHeartRateCallbackThreshold.

The following constants are available for this function:

  • BRICKLET_HEART_RATE_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_HEART_RATE_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_HEART_RATE_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_HEART_RATE_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_HEART_RATE_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletHeartRate.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 TBrickletHeartRate.GetDebouncePeriod: longword

Returns the debounce period as set by SetDebouncePeriod.

procedure TBrickletHeartRate.EnableBeatStateChangedCallback

Enables the OnBeatStateChanged callback.

procedure TBrickletHeartRate.DisableBeatStateChangedCallback

Disables the OnBeatStateChanged callback.

function TBrickletHeartRate.IsBeatStateChangedCallbackEnabled: boolean

Returns true if the OnBeatStateChanged callback is enabled.

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

heartRate.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 TBrickletHeartRate.OnHeartRate
procedure(sender: TBrickletHeartRate; const heartRate: word) of object;

This callback is triggered periodically with the period that is set by SetHeartRateCallbackPeriod. The parameter is the heart rate of the sensor.

OnHeartRate is only triggered if the heart rate has changed since the last triggering.

property TBrickletHeartRate.OnHeartRateReached
procedure(sender: TBrickletHeartRate; const heartRate: word) of object;

This callback is triggered when the threshold as set by SetHeartRateCallbackThreshold is reached. The parameter is the heart rate of the sensor.

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

property TBrickletHeartRate.OnBeatStateChanged
procedure(sender: TBrickletHeartRate; const state: byte) of object;

This callback provides the current heart beat state.It is called every time a heart beat is detected. The state can either be

  • 0 = Falling: The falling edge of a detected heart beat.
  • 1 = Rising: The rising edge of a detected heart beat.

The following constants are available for this function:

  • BRICKLET_HEART_RATE_BEAT_STATE_FALLING = 0
  • BRICKLET_HEART_RATE_BEAT_STATE_RISING = 1

Constants

const BRICKLET_HEART_RATE_DEVICE_IDENTIFIER

This constant is used to identify a Heart Rate 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.

Creative Commons Licence The content of this page is licensed under Creative Commons Attribution 3.0 Unported License.