Delphi/Lazarus - Load Cell Bricklet

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

type
  TExample = class
  private
    ipcon: TIPConnection;
    lc: TBrickletLoadCell;
  public
    procedure Execute;
  end;

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

var
  e: TExample;

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

  { Create device object }
  lc := TBrickletLoadCell.Create(UID, ipcon);

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

  { Get current weight }
  weight := lc.GetWeight;
  WriteLn(Format('Weight: %d g', [weight]));

  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, BrickletLoadCell;

type
  TExample = class
  private
    ipcon: TIPConnection;
    lc: TBrickletLoadCell;
  public
    procedure WeightCB(sender: TBrickletLoadCell; const weight: longint);
    procedure Execute;
  end;

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

var
  e: TExample;

{ Callback procedure for weight callback }
procedure TExample.WeightCB(sender: TBrickletLoadCell; const weight: longint);
begin
  WriteLn(Format('Weight: %d g', [weight]));
end;

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

  { Create device object }
  lc := TBrickletLoadCell.Create(UID, ipcon);

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

  { Register weight callback to procedure WeightCB }
  lc.OnWeight := {$ifdef FPC}@{$endif}WeightCB;

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

type
  TExample = class
  private
    ipcon: TIPConnection;
    lc: TBrickletLoadCell;
  public
    procedure WeightReachedCB(sender: TBrickletLoadCell; const weight: longint);
    procedure Execute;
  end;

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

var
  e: TExample;

{ Callback procedure for weight reached callback }
procedure TExample.WeightReachedCB(sender: TBrickletLoadCell; const weight: longint);
begin
  WriteLn(Format('Weight: %d g', [weight]));
end;

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

  { Create device object }
  lc := TBrickletLoadCell.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 1 second (1000ms) }
  lc.SetDebouncePeriod(1000);

  { Register weight reached callback to procedure WeightReachedCB }
  lc.OnWeightReached := {$ifdef FPC}@{$endif}WeightReachedCB;

  { Configure threshold for weight "greater than 200 g" }
  lc.SetWeightCallbackThreshold('>', 200, 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 TBrickletLoadCell.Create(const uid: string; ipcon: TIPConnection)
Parameters:
  • uid – Type: string
  • ipcon – Type: TIPConnection
Returns:
  • loadCell – Type: TBrickletLoadCell

Creates an object with the unique device ID uid:

loadCell := TBrickletLoadCell.Create('YOUR_DEVICE_UID', ipcon);

This object can then be used after the IP Connection is connected.

function TBrickletLoadCell.GetWeight: longint
Returns:
  • weight – Type: longint, Unit: 1 g, Range: [-231 to 231 - 1]

Returns the currently measured weight.

If you want to get the weight periodically, it is recommended to use the OnWeight callback and set the period with SetWeightCallbackPeriod.

procedure TBrickletLoadCell.LEDOn

Turns the LED on.

procedure TBrickletLoadCell.LEDOff

Turns the LED off.

function TBrickletLoadCell.IsLEDOn: boolean
Returns:
  • on – Type: boolean, Default: false

Returns true if the led is on, false otherwise.

procedure TBrickletLoadCell.Tare

Sets the currently measured weight as tare weight.

Advanced Functions

procedure TBrickletLoadCell.SetMovingAverage(const average: byte)
Parameters:
  • average – Type: byte, Range: [1 to 40], Default: 4

Sets the length of a moving averaging for the weight value.

Setting the length to 1 will turn the averaging off. With less averaging, there is more noise on the data.

function TBrickletLoadCell.GetMovingAverage: byte
Returns:
  • average – Type: byte, Range: [1 to 40], Default: 4

Returns the length moving average as set by SetMovingAverage.

procedure TBrickletLoadCell.Calibrate(const weight: longword)
Parameters:
  • weight – Type: longword, Unit: 1 g, Range: [0 to 232 - 1]

To calibrate your Load Cell Bricklet you have to

  • empty the scale and call this function with 0 and
  • add a known weight to the scale and call this function with the weight.

The calibration is saved in the EEPROM of the Bricklet and only needs to be done once.

We recommend to use the Brick Viewer for calibration, you don't need to call this function in your source code.

procedure TBrickletLoadCell.SetConfiguration(const rate: byte; const gain: byte)
Parameters:
  • rate – Type: byte, Range: See constants, Default: 0
  • gain – Type: byte, Range: See constants, Default: 0

The measurement rate and gain are configurable.

The rate can be either 10Hz or 80Hz. A faster rate will produce more noise. It is additionally possible to add a moving average (see SetMovingAverage) to the measurements.

The gain can be 128x, 64x or 32x. It represents a measurement range of ±20mV, ±40mV and ±80mV respectively. The Load Cell Bricklet uses an excitation voltage of 5V and most load cells use an output of 2mV/V. That means the voltage range is ±15mV for most load cells (i.e. gain of 128x is best). If you don't know what all of this means you should keep it at 128x, it will most likely be correct.

The configuration is saved in the EEPROM of the Bricklet and only needs to be done once.

We recommend to use the Brick Viewer for configuration, you don't need to call this function in your source code.

The following constants are available for this function:

For rate:

  • BRICKLET_LOAD_CELL_RATE_10HZ = 0
  • BRICKLET_LOAD_CELL_RATE_80HZ = 1

For gain:

  • BRICKLET_LOAD_CELL_GAIN_128X = 0
  • BRICKLET_LOAD_CELL_GAIN_64X = 1
  • BRICKLET_LOAD_CELL_GAIN_32X = 2
procedure TBrickletLoadCell.GetConfiguration(out rate: byte; out gain: byte)
Output Parameters:
  • rate – Type: byte, Range: See constants, Default: 0
  • gain – Type: byte, Range: See constants, Default: 0

Returns the configuration as set by SetConfiguration.

The following constants are available for this function:

For rate:

  • BRICKLET_LOAD_CELL_RATE_10HZ = 0
  • BRICKLET_LOAD_CELL_RATE_80HZ = 1

For gain:

  • BRICKLET_LOAD_CELL_GAIN_128X = 0
  • BRICKLET_LOAD_CELL_GAIN_64X = 1
  • BRICKLET_LOAD_CELL_GAIN_32X = 2
procedure TBrickletLoadCell.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)
Output Parameters:
  • uid – Type: string, Length: up to 8
  • connectedUid – Type: string, Length: up to 8
  • position – Type: char, Range: ['a' to 'h', 'i', 'z']
  • hardwareVersion – Type: array [0..2] of byte
    • 0: major – Type: byte, Range: [0 to 255]
    • 1: minor – Type: byte, Range: [0 to 255]
    • 2: revision – Type: byte, Range: [0 to 255]
  • firmwareVersion – Type: array [0..2] of byte
    • 0: major – Type: byte, Range: [0 to 255]
    • 1: minor – Type: byte, Range: [0 to 255]
    • 2: revision – Type: byte, Range: [0 to 255]
  • deviceIdentifier – Type: word, Range: [0 to 216 - 1]

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', 'd', 'e', 'f', 'g' or 'h' (Bricklet Port). The Raspberry Pi HAT (Zero) Brick is always at position 'i' and the Bricklet connected to an Isolator Bricklet is always as position 'z'.

The device identifier numbers can be found here. There is also a constant for the device identifier of this Bricklet.

Callback Configuration Functions

procedure TBrickletLoadCell.SetWeightCallbackPeriod(const period: longword)
Parameters:
  • period – Type: longword, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

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

The OnWeight callback is only triggered if the weight has changed since the last triggering.

function TBrickletLoadCell.GetWeightCallbackPeriod: longword
Returns:
  • period – Type: longword, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0

Returns the period as set by SetWeightCallbackPeriod.

procedure TBrickletLoadCell.SetWeightCallbackThreshold(const option: char; const min: longint; const max: longint)
Parameters:
  • option – Type: char, Range: See constants, Default: 'x'
  • min – Type: longint, Unit: 1 g, Range: [-231 to 231 - 1], Default: 0
  • max – Type: longint, Unit: 1 g, Range: [-231 to 231 - 1], Default: 0

Sets the thresholds for the OnWeightReached callback.

The following options are possible:

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

The following constants are available for this function:

For option:

  • BRICKLET_LOAD_CELL_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_LOAD_CELL_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_LOAD_CELL_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_LOAD_CELL_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_LOAD_CELL_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletLoadCell.GetWeightCallbackThreshold(out option: char; out min: longint; out max: longint)
Output Parameters:
  • option – Type: char, Range: See constants, Default: 'x'
  • min – Type: longint, Unit: 1 g, Range: [-231 to 231 - 1], Default: 0
  • max – Type: longint, Unit: 1 g, Range: [-231 to 231 - 1], Default: 0

Returns the threshold as set by SetWeightCallbackThreshold.

The following constants are available for this function:

For option:

  • BRICKLET_LOAD_CELL_THRESHOLD_OPTION_OFF = 'x'
  • BRICKLET_LOAD_CELL_THRESHOLD_OPTION_OUTSIDE = 'o'
  • BRICKLET_LOAD_CELL_THRESHOLD_OPTION_INSIDE = 'i'
  • BRICKLET_LOAD_CELL_THRESHOLD_OPTION_SMALLER = '<'
  • BRICKLET_LOAD_CELL_THRESHOLD_OPTION_GREATER = '>'
procedure TBrickletLoadCell.SetDebouncePeriod(const debounce: longword)
Parameters:
  • debounce – Type: longword, Unit: 1 ms, Range: [0 to 232 - 1], Default: 100

Sets the period with which the threshold callback

is triggered, if the threshold

keeps being reached.

function TBrickletLoadCell.GetDebouncePeriod: longword
Returns:
  • debounce – Type: longword, Unit: 1 ms, Range: [0 to 232 - 1], Default: 100

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: TBrickletLoadCell; const value: longint);
begin
  WriteLn(Format('Value: %d', [value]));
end;

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

The available callback properties and their parameter types 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 TBrickletLoadCell.OnWeight
procedure(sender: TBrickletLoadCell; const weight: longint) of object;
Callback Parameters:
  • sender – Type: TBrickletLoadCell
  • weight – Type: longint, Unit: 1 g, Range: [-231 to 231 - 1]

This callback is triggered periodically with the period that is set by SetWeightCallbackPeriod. The parameter is the weight as measured by the load cell.

The OnWeight callback is only triggered if the weight has changed since the last triggering.

property TBrickletLoadCell.OnWeightReached
procedure(sender: TBrickletLoadCell; const weight: longint) of object;
Callback Parameters:
  • sender – Type: TBrickletLoadCell
  • weight – Type: longint, Unit: 1 g, Range: [-231 to 231 - 1]

This callback is triggered when the threshold as set by SetWeightCallbackThreshold is reached. The parameter is the weight as measured by the load cell.

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

Virtual Functions

Virtual functions don't communicate with the device itself, but operate only on the API bindings device object. They can be called without the corresponding IP Connection object being connected.

function TBrickletLoadCell.GetAPIVersion: array [0..2] of byte
Output Parameters:
  • apiVersion – Type: array [0..2] of byte
    • 0: major – Type: byte, Range: [0 to 255]
    • 1: minor – Type: byte, Range: [0 to 255]
    • 2: revision – Type: byte, Range: [0 to 255]

Returns the version of the API definition 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 TBrickletLoadCell.GetResponseExpected(const functionId: byte): boolean
Parameters:
  • functionId – Type: byte, Range: See constants
Returns:
  • responseExpected – Type: 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 sent and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

For functionId:

  • BRICKLET_LOAD_CELL_FUNCTION_SET_WEIGHT_CALLBACK_PERIOD = 2
  • BRICKLET_LOAD_CELL_FUNCTION_SET_WEIGHT_CALLBACK_THRESHOLD = 4
  • BRICKLET_LOAD_CELL_FUNCTION_SET_DEBOUNCE_PERIOD = 6
  • BRICKLET_LOAD_CELL_FUNCTION_SET_MOVING_AVERAGE = 8
  • BRICKLET_LOAD_CELL_FUNCTION_LED_ON = 10
  • BRICKLET_LOAD_CELL_FUNCTION_LED_OFF = 11
  • BRICKLET_LOAD_CELL_FUNCTION_CALIBRATE = 13
  • BRICKLET_LOAD_CELL_FUNCTION_TARE = 14
  • BRICKLET_LOAD_CELL_FUNCTION_SET_CONFIGURATION = 15
procedure TBrickletLoadCell.SetResponseExpected(const functionId: byte; const responseExpected: boolean)
Parameters:
  • functionId – Type: byte, Range: See constants
  • responseExpected – Type: 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 sent and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

For functionId:

  • BRICKLET_LOAD_CELL_FUNCTION_SET_WEIGHT_CALLBACK_PERIOD = 2
  • BRICKLET_LOAD_CELL_FUNCTION_SET_WEIGHT_CALLBACK_THRESHOLD = 4
  • BRICKLET_LOAD_CELL_FUNCTION_SET_DEBOUNCE_PERIOD = 6
  • BRICKLET_LOAD_CELL_FUNCTION_SET_MOVING_AVERAGE = 8
  • BRICKLET_LOAD_CELL_FUNCTION_LED_ON = 10
  • BRICKLET_LOAD_CELL_FUNCTION_LED_OFF = 11
  • BRICKLET_LOAD_CELL_FUNCTION_CALIBRATE = 13
  • BRICKLET_LOAD_CELL_FUNCTION_TARE = 14
  • BRICKLET_LOAD_CELL_FUNCTION_SET_CONFIGURATION = 15
procedure TBrickletLoadCell.SetResponseExpectedAll(const responseExpected: boolean)
Parameters:
  • responseExpected – Type: boolean

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

Constants

const BRICKLET_LOAD_CELL_DEVICE_IDENTIFIER

This constant is used to identify a Load Cell Bricklet.

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

const BRICKLET_LOAD_CELL_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Load Cell Bricklet.