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 Laser Range Finder Bricklet. General information and technical specifications for the Laser Range Finder Bricklet are summarized in its hardware description.
An installation guide for the Delphi/Lazarus API bindings is part of their general description.
The example code below is Public Domain (CC0 1.0).
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 | program ExampleSimple;
{$ifdef MSWINDOWS}{$apptype CONSOLE}{$endif}
{$ifdef FPC}{$mode OBJFPC}{$H+}{$endif}
uses
SysUtils, IPConnection, BrickletLaserRangeFinder;
type
TExample = class
private
ipcon: TIPConnection;
lrf: TBrickletLaserRangeFinder;
public
procedure Execute;
end;
const
HOST = 'localhost';
PORT = 4223;
UID = 'XYZ'; { Change to your UID }
var
e: TExample;
procedure TExample.Execute;
var distance: word;
begin
{ Create IP connection }
ipcon := TIPConnection.Create;
{ Create device object }
lrf := TBrickletLaserRangeFinder.Create(UID, ipcon);
{ Connect to brickd }
ipcon.Connect(HOST, PORT);
{ Don't use device before ipcon is connected }
{ Turn laser on and wait 250ms for very first measurement to be ready }
lrf.EnableLaser;
Sleep(250);
{ Get current distance (unit is cm) }
distance := lrf.GetDistance;
WriteLn(Format('Distance: %d cm', [distance]));
WriteLn('Press key to exit');
ReadLn;
ipcon.Destroy; { Calls ipcon.Disconnect internally }
end;
begin
e := TExample.Create;
e.Execute;
e.Destroy;
end.
|
Download (ExampleCallback.pas)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 | program ExampleCallback;
{$ifdef MSWINDOWS}{$apptype CONSOLE}{$endif}
{$ifdef FPC}{$mode OBJFPC}{$H+}{$endif}
uses
SysUtils, IPConnection, BrickletLaserRangeFinder;
type
TExample = class
private
ipcon: TIPConnection;
lrf: TBrickletLaserRangeFinder;
public
procedure DistanceCB(sender: TBrickletLaserRangeFinder; const distance: word);
procedure Execute;
end;
const
HOST = 'localhost';
PORT = 4223;
UID = 'XYZ'; { Change to your UID }
var
e: TExample;
{ Callback function for distance callback (parameter has unit cm) }
procedure TExample.DistanceCB(sender: TBrickletLaserRangeFinder; const distance: word);
begin
WriteLn(Format('Distance: %d cm', [distance]));
end;
procedure TExample.Execute;
begin
{ Create IP connection }
ipcon := TIPConnection.Create;
{ Create device object }
lrf := TBrickletLaserRangeFinder.Create(UID, ipcon);
{ Connect to brickd }
ipcon.Connect(HOST, PORT);
{ Don't use device before ipcon is connected }
{ Turn laser on and wait 250ms for very first measurement to be ready }
lrf.EnableLaser;
Sleep(250);
{ Set Period for distance callback to 1s (1000ms)
Note: The distance callback is only called every second if the
distance has changed since the last call! }
lrf.SetDistanceCallbackPeriod(1000);
{ Register distance callback to procedure DistanceCB }
lrf.OnDistance := {$ifdef FPC}@{$endif}DistanceCB;
WriteLn('Press key to exit');
ReadLn;
ipcon.Destroy; { Calls ipcon.Disconnect internally }
end;
begin
e := TExample.Create;
e.Execute;
e.Destroy;
end.
|
Download (ExampleThreshold.pas)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 | program ExampleThreshold;
{$ifdef MSWINDOWS}{$apptype CONSOLE}{$endif}
{$ifdef FPC}{$mode OBJFPC}{$H+}{$endif}
uses
SysUtils, IPConnection, BrickletLaserRangeFinder;
type
TExample = class
private
ipcon: TIPConnection;
lrf: TBrickletLaserRangeFinder;
public
procedure ReachedCB(sender: TBrickletLaserRangeFinder; const distance: word);
procedure Execute;
end;
const
HOST = 'localhost';
PORT = 4223;
UID = 'XYZ'; { Change to your UID }
var
e: TExample;
{ Callback for distance greater than 20 cm }
procedure TExample.ReachedCB(sender: TBrickletLaserRangeFinder; const distance: word);
begin
WriteLn(Format('Distance: %d cm.', [distance]));
end;
procedure TExample.Execute;
begin
{ Create IP connection }
ipcon := TIPConnection.Create;
{ Create device object }
lrf := TBrickletLaserRangeFinder.Create(UID, ipcon);
{ Connect to brickd }
ipcon.Connect(HOST, PORT);
{ Don't use device before ipcon is connected }
{ Turn laser on and wait 250ms for very first measurement to be ready }
lrf.EnableLaser;
Sleep(250);
{ Get threshold callbacks with a debounce time of 10 seconds (10000ms) }
lrf.SetDebouncePeriod(10000);
{ Register threshold reached callback to procedure ReachedCB }
lrf.OnDistanceReached := {$ifdef FPC}@{$endif}ReachedCB;
{ Configure threshold for "greater than 20 cm" }
lrf.SetDistanceCallbackThreshold('>', 20, 0);
WriteLn('Press key to exit');
ReadLn;
ipcon.Destroy; { Calls ipcon.Disconnect internally }
end;
begin
e := TExample.Create;
e.Execute;
e.Destroy;
end.
|
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.
Creates an object with the unique device ID uid:
laserRangeFinder := TBrickletLaserRangeFinder.Create('YOUR_DEVICE_UID', ipcon);
This object can then be used after the IP Connection is connected (see examples above).
Returns the measured distance. The value has a range of 0 to 4000 and is given in cm.
The Laser Range Finder Bricklet knows different modes. Distances are only measured in the distance measurement mode, see SetMode. Also the laser has to be enabled, see EnableLaser.
If you want to get the distance periodically, it is recommended to use the callback OnDistance and set the period with SetDistanceCallbackPeriod.
Returns the measured velocity. The value has a range of 0 to 12700 and is given in 1/100 m/s.
The Laser Range Finder Bricklet knows different modes. Velocity is only measured in the velocity measurement modes, see SetMode. Also the laser has to be enabled, see EnableLaser.
If you want to get the velocity periodically, it is recommended to use the callback OnVelocity and set the period with SetVelocityCallbackPeriod.
The LIDAR has five different modes. One mode is for distance measurements and four modes are for velocity measurements with different ranges.
The following modes are available:
The default mode is 0 (distance is measured).
The following constants are available for this function:
Returns the mode as set by SetMode.
The following constants are available for this function:
Activates the laser of the LIDAR.
We recommend that you wait 250ms after enabling the laser before the first call of GetDistance to ensure stable measurements.
Deactivates the laser of the LIDAR.
Returns true if the laser is enabled, false otherwise.
Sets the length of a moving averaging for the distance and velocity.
Setting the length to 0 will turn the averaging completely off. With less averaging, there is more noise on the data.
The range for the averaging is 0-30.
The default value is 10.
Returns the length moving average as set by SetMovingAverage.
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.
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.
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:
Changes the response expected flag for all setter and callback configuration functions of this device at once.
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.
Sets the period in ms with which the OnDistance callback is triggered periodically. A value of 0 turns the callback off.
OnDistance is only triggered if the distance value has changed since the last triggering.
The default value is 0.
Returns the period as set by SetDistanceCallbackPeriod.
Sets the period in ms with which the OnVelocity callback is triggered periodically. A value of 0 turns the callback off.
OnVelocity is only triggered if the velocity value has changed since the last triggering.
The default value is 0.
Returns the period as set by SetVelocityCallbackPeriod.
Sets the thresholds for the OnDistanceReached callback.
The following options are possible:
Option | Description |
---|---|
'x' | Callback is turned off |
'o' | Callback is triggered when the distance value is outside the min and max values |
'i' | Callback is triggered when the distance value is inside the min and max values |
'<' | Callback is triggered when the distance value is smaller than the min value (max is ignored) |
'>' | Callback is triggered when the distance value is greater than the min value (max is ignored) |
The default value is ('x', 0, 0).
The following constants are available for this function:
Returns the threshold as set by SetDistanceCallbackThreshold.
The following constants are available for this function:
Sets the thresholds for the OnVelocityReached callback.
The following options are possible:
Option | Description |
---|---|
'x' | Callback is turned off |
'o' | Callback is triggered when the velocity is outside the min and max values |
'i' | Callback is triggered when the velocity is inside the min and max values |
'<' | Callback is triggered when the velocity is smaller than the min value (max is ignored) |
'>' | Callback is triggered when the velocity is greater than the min value (max is ignored) |
The default value is ('x', 0, 0).
The following constants are available for this function:
Returns the threshold as set by SetVelocityCallbackThreshold.
The following constants are available for this function:
Sets the period in ms with which the threshold callbacks
are triggered, if the thresholds
keep being reached.
The default value is 100.
Returns the debounce period as set by SetDebouncePeriod.
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: TBrickletLaserRangeFinder; const param: word); begin WriteLn(param); end; laserRangeFinder.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.
procedure(sender: TBrickletLaserRangeFinder; const distance: word) of object;
This callback is triggered periodically with the period that is set by SetDistanceCallbackPeriod. The parameter is the distance value of the sensor.
OnDistance is only triggered if the distance value has changed since the last triggering.
procedure(sender: TBrickletLaserRangeFinder; const velocity: smallint) of object;
This callback is triggered periodically with the period that is set by SetVelocityCallbackPeriod. The parameter is the velocity value of the sensor.
OnVelocity is only triggered if the velocity has changed since the last triggering.
procedure(sender: TBrickletLaserRangeFinder; const distance: word) of object;
This callback is triggered when the threshold as set by SetDistanceCallbackThreshold is reached. The parameter is the distance value of the sensor.
If the threshold keeps being reached, the callback is triggered periodically with the period as set by SetDebouncePeriod.
procedure(sender: TBrickletLaserRangeFinder; const velocity: smallint) of object;
This callback is triggered when the threshold as set by SetVelocityCallbackThreshold is reached. The parameter is the velocity value of the sensor.
If the threshold keeps being reached, the callback is triggered periodically with the period as set by SetDebouncePeriod.
This constant is used to identify a Laser Range Finder 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.