PHP - Distance US Bricklet

This is the description of the PHP API bindings for the Distance US Bricklet. General information and technical specifications for the Distance US Bricklet are summarized in its hardware description.

An installation guide for the PHP API bindings is part of their general description.

Examples

The example code below is Public Domain (CC0 1.0).

Simple

Download (ExampleSimple.php)

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<?php

require_once('Tinkerforge/IPConnection.php');
require_once('Tinkerforge/BrickletDistanceUS.php');

use Tinkerforge\IPConnection;
use Tinkerforge\BrickletDistanceUS;

const HOST = 'localhost';
const PORT = 4223;
const UID = 'XYZ'; // Change XYZ to the UID of your Distance US Bricklet

$ipcon = new IPConnection(); // Create IP connection
$dus = new BrickletDistanceUS(UID, $ipcon); // Create device object

$ipcon->connect(HOST, PORT); // Connect to brickd
// Don't use device before ipcon is connected

// Get current distance value
$distance = $dus->getDistanceValue();
echo "Distance Value: $distance\n";

echo "Press key to exit\n";
fgetc(fopen('php://stdin', 'r'));
$ipcon->disconnect();

?>

Callback

Download (ExampleCallback.php)

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<?php

require_once('Tinkerforge/IPConnection.php');
require_once('Tinkerforge/BrickletDistanceUS.php');

use Tinkerforge\IPConnection;
use Tinkerforge\BrickletDistanceUS;

const HOST = 'localhost';
const PORT = 4223;
const UID = 'XYZ'; // Change XYZ to the UID of your Distance US Bricklet

// Callback function for distance value callback
function cb_distance($distance)
{
    echo "Distance Value: $distance\n";
}

$ipcon = new IPConnection(); // Create IP connection
$dus = new BrickletDistanceUS(UID, $ipcon); // Create device object

$ipcon->connect(HOST, PORT); // Connect to brickd
// Don't use device before ipcon is connected

// Register distance value callback to function cb_distance
$dus->registerCallback(BrickletDistanceUS::CALLBACK_DISTANCE, 'cb_distance');

// Set period for distance value callback to 0.2s (200ms)
// Note: The distance value callback is only called every 0.2 seconds
//       if the distance value has changed since the last call!
$dus->setDistanceCallbackPeriod(200);

echo "Press ctrl+c to exit\n";
$ipcon->dispatchCallbacks(-1); // Dispatch callbacks forever

?>

Threshold

Download (ExampleThreshold.php)

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<?php

require_once('Tinkerforge/IPConnection.php');
require_once('Tinkerforge/BrickletDistanceUS.php');

use Tinkerforge\IPConnection;
use Tinkerforge\BrickletDistanceUS;

const HOST = 'localhost';
const PORT = 4223;
const UID = 'XYZ'; // Change XYZ to the UID of your Distance US Bricklet

// Callback function for distance value reached callback
function cb_distanceReached($distance)
{
    echo "Distance Value: $distance\n";
}

$ipcon = new IPConnection(); // Create IP connection
$dus = new BrickletDistanceUS(UID, $ipcon); // Create device object

$ipcon->connect(HOST, PORT); // Connect to brickd
// Don't use device before ipcon is connected

// Get threshold callbacks with a debounce time of 10 seconds (10000ms)
$dus->setDebouncePeriod(10000);

// Register distance value reached callback to function cb_distanceReached
$dus->registerCallback(BrickletDistanceUS::CALLBACK_DISTANCE_REACHED,
                       'cb_distanceReached');

// Configure threshold for distance value "smaller than 200"
$dus->setDistanceCallbackThreshold('<', 200, 0);

echo "Press ctrl+c to exit\n";
$ipcon->dispatchCallbacks(-1); // Dispatch callbacks forever

?>

API

Functions that return multiple values return them in an associative array.

Basic Functions

class BrickletDistanceUS(string $uid, IPConnection $ipcon)

Creates an object with the unique device ID $uid:

<?php   $distance_us = new BrickletDistanceUS('YOUR_DEVICE_UID', $ipcon);   ?>

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

int BrickletDistanceUS::getDistanceValue()

Returns the current distance value measured by the sensor. The value has a range of 0 to 4095. A small value corresponds to a small distance, a big value corresponds to a big distance. The relation between the measured distance value and the actual distance is affected by the 5V supply voltage (deviations in the supply voltage result in deviations in the distance values) and is non-linear (resolution is bigger at close range).

If you want to get the distance value periodically, it is recommended to use the CALLBACK_DISTANCE callback and set the period with setDistanceCallbackPeriod().

Advanced Functions

void BrickletDistanceUS::setMovingAverage(int $average)

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

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 0-100.

The default value is 20.

int BrickletDistanceUS::getMovingAverage()

Returns the length moving average as set by setMovingAverage().

array BrickletDistanceUS::getAPIVersion()

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.

bool BrickletDistanceUS::getResponseExpected(int $function_id)

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.

The following constants are available for this function:

  • BrickletDistanceUS::FUNCTION_SET_DISTANCE_CALLBACK_PERIOD = 2
  • BrickletDistanceUS::FUNCTION_SET_DISTANCE_CALLBACK_THRESHOLD = 4
  • BrickletDistanceUS::FUNCTION_SET_DEBOUNCE_PERIOD = 6
  • BrickletDistanceUS::FUNCTION_SET_MOVING_AVERAGE = 10
void BrickletDistanceUS::setResponseExpected(int $function_id, bool $response_expected)

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 constants are available for this function:

  • BrickletDistanceUS::FUNCTION_SET_DISTANCE_CALLBACK_PERIOD = 2
  • BrickletDistanceUS::FUNCTION_SET_DISTANCE_CALLBACK_THRESHOLD = 4
  • BrickletDistanceUS::FUNCTION_SET_DEBOUNCE_PERIOD = 6
  • BrickletDistanceUS::FUNCTION_SET_MOVING_AVERAGE = 10
void BrickletDistanceUS::setResponseExpectedAll(bool $response_expected)

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

array BrickletDistanceUS::getIdentity()

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.

The returned array has the keys uid, connected_uid, position, hardware_version, firmware_version and device_identifier.

Callback Configuration Functions

void BrickletDistanceUS::registerCallback(int $callback_id, callable $callback, mixed $user_data=NULL)

Registers the given $function with the given $callback_id. The optional $user_data will be passed as the last parameter to the function.

The available callback IDs with corresponding function signatures are listed below.

void BrickletDistanceUS::setDistanceCallbackPeriod(int $period)

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

Der CALLBACK_DISTANCE callback is only triggered if the distance value has changed since the last triggering.

The default value is 0.

int BrickletDistanceUS::getDistanceCallbackPeriod()

Returns the period as set by setDistanceCallbackPeriod().

void BrickletDistanceUS::setDistanceCallbackThreshold(string $option, int $min, int $max)

Sets the thresholds for the CALLBACK_DISTANCE_REACHED 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:

  • BrickletDistanceUS::THRESHOLD_OPTION_OFF = 'x'
  • BrickletDistanceUS::THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletDistanceUS::THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletDistanceUS::THRESHOLD_OPTION_SMALLER = '<'
  • BrickletDistanceUS::THRESHOLD_OPTION_GREATER = '>'
array BrickletDistanceUS::getDistanceCallbackThreshold()

Returns the threshold as set by setDistanceCallbackThreshold().

The following constants are available for this function:

  • BrickletDistanceUS::THRESHOLD_OPTION_OFF = 'x'
  • BrickletDistanceUS::THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletDistanceUS::THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletDistanceUS::THRESHOLD_OPTION_SMALLER = '<'
  • BrickletDistanceUS::THRESHOLD_OPTION_GREATER = '>'

The returned array has the keys option, min and max.

void BrickletDistanceUS::setDebouncePeriod(int $debounce)

Sets the period in ms with which the threshold callbacks

are triggered, if the thresholds

keep being reached.

The default value is 100.

int BrickletDistanceUS::getDebouncePeriod()

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 with the registerCallback() function of the device object. The first parameter is the callback ID and the second parameter the callback function:

<?php

function myCallback($param)
{
    echo $param . "\n";
}

$distance_us->registerCallback(BrickletDistanceUS::CALLBACK_EXAMPLE, 'myCallback');

?>

The available constants with corresponding function signatures 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.

int BrickletDistanceUS::CALLBACK_DISTANCE
<?php   void callback(int $distance [, mixed $user_data])   ?>

This callback is triggered periodically with the period that is set by setDistanceCallbackPeriod(). The parameter is the distance value of the sensor.

The CALLBACK_DISTANCE callback is only triggered if the distance value has changed since the last triggering.

int BrickletDistanceUS::CALLBACK_DISTANCE_REACHED
<?php   void callback(int $distance [, mixed $user_data])   ?>

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().

Constants

int BrickletDistanceUS::DEVICE_IDENTIFIER

This constant is used to identify a Distance US Bricklet.

The getIdentity() function and the IPConnection::CALLBACK_ENUMERATE callback of the IP Connection have a deviceIdentifier parameter to specify the Brick's or Bricklet's type.

string BrickletDistanceUS::DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Distance US Bricklet.