PHP - LED Strip Bricklet

This is the description of the PHP API bindings for the LED Strip Bricklet. General information and technical specifications for the LED Strip 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/BrickletLEDStrip.php');

use Tinkerforge\IPConnection;
use Tinkerforge\BrickletLEDStrip;

const HOST = 'localhost';
const PORT = 4223;
const UID = 'XYZ'; // Change to your UID

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

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

// Set first 10 LEDs to green
$r = array(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0);
$g = array(255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 0, 0, 0, 0, 0, 0);
$b = array(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0);
$ledStrip->setRGBValues(0, 10, $r, $g, $b);

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/BrickletLEDStrip.php');

use Tinkerforge\IPConnection;
use Tinkerforge\BrickletLEDStrip;

const HOST = 'localhost';
const PORT = 4223;
const UID = 'XYZ'; // Change to your UID
const NUM_LEDS = 16;

$r = array(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0);
$g = array(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0);
$b = array(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0);
$rIndex = 0;

// Frame rendered callback, is called when a new frame was rendered
// We increase the index of one blue LED with every frame
function cb_frameRendered($length)
{
    global $rIndex, $r, $g, $b, $ledStrip;

    $b[$rIndex] = 0;

    if ($rIndex == NUM_LEDS - 1) {
        $rIndex = 0;
    } else {
        $rIndex++;
    }

    $b[$rIndex] = 255;

    $ledStrip->setRGBValues(0, NUM_LEDS, $r, $g, $b);
}

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

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

// Set frame duration to 50ms (20 frames per second)
$ledStrip->setFrameDuration(50);

// Register frame rendered callback to function cb_frame_rendered
$ledStrip->registerCallback(BrickletLEDStrip::CALLBACK_FRAME_RENDERED, 'cb_frameRendered');

// Set initial rgb values to get started
$ledStrip->setRGBValues(0, NUM_LEDS, $r, $g, $b);

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 BrickletLEDStrip(string $uid, IPConnection $ipcon)

Creates an object with the unique device ID $uid:

<?php   $led_strip = new BrickletLEDStrip('YOUR_DEVICE_UID', $ipcon);   ?>

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

void BrickletLEDStrip::setRGBValues(int $index, int $length, array $r, array $g, array $b)

Sets the rgb values for the LEDs with the given length starting from index.

The maximum length is 16, the index goes from 0 to 319 and the rgb values have 8 bits each.

Example: If you set

  • index to 5,
  • length to 3,
  • r to array(255, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0),
  • g to array(0, 255, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0) and
  • b to array(0, 0, 255, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)

the LED with index 5 will be red, 6 will be green and 7 will be blue.

Note

Depending on the LED circuitry colors can be permuted.

The colors will be transfered to actual LEDs when the next frame duration ends, see setFrameDuration().

Generic approach:

  • Set the frame duration to a value that represents the number of frames per second you want to achieve.
  • Set all of the LED colors for one frame.
  • Wait for the CALLBACK_FRAME_RENDERED callback.
  • Set all of the LED colors for next frame.
  • Wait for the CALLBACK_FRAME_RENDERED callback.
  • and so on.

This approach ensures that you can change the LED colors with a fixed frame rate.

The actual number of controllable LEDs depends on the number of free Bricklet ports. See here for more information. A call of setRGBValues() with index + length above the bounds is ignored completely.

array BrickletLEDStrip::getRGBValues(int $index, int $length)

Returns the rgb with the given length starting from the given index.

The values are the last values that were set by setRGBValues().

The returned array has the keys r, g and b.

void BrickletLEDStrip::setFrameDuration(int $duration)

Sets the frame duration in ms.

Example: If you want to achieve 20 frames per second, you should set the frame duration to 50ms (50ms * 20 = 1 second).

For an explanation of the general approach see setRGBValues().

Default value: 100ms (10 frames per second).

int BrickletLEDStrip::getFrameDuration()

Returns the frame duration as set by setFrameDuration().

int BrickletLEDStrip::getSupplyVoltage()

Returns the current supply voltage of the LEDs. The voltage is given in mV.

void BrickletLEDStrip::setClockFrequency(int $frequency)

Sets the frequency of the clock in Hz. The range is 10000Hz (10kHz) up to 2000000Hz (2MHz).

The Bricklet will choose the nearest achievable frequency, which may be off by a few Hz. You can get the exact frequency that is used by calling getClockFrequency().

If you have problems with flickering LEDs, they may be bits flipping. You can fix this by either making the connection between the LEDs and the Bricklet shorter or by reducing the frequency.

With a decreasing frequency your maximum frames per second will decrease too.

The default value is 1.66MHz.

Note

The frequency in firmware version 2.0.0 is fixed at 2MHz.

New in version 2.0.1 (Plugin).

int BrickletLEDStrip::getClockFrequency()

Returns the currently used clock frequency as set by setClockFrequency().

New in version 2.0.1 (Plugin).

void BrickletLEDStrip::setChipType(int $chip)

Sets the type of the led driver chip. We currently support the chips

  • WS2801 (chip = 2801),
  • WS2811 (chip = 2811) and
  • WS2812 (chip = 2812).

The WS2812 is sometimes also called "NeoPixel", a name coined by Adafruit.

The default value is WS2801 (chip = 2801).

The following constants are available for this function:

  • BrickletLEDStrip::CHIP_TYPE_WS2801 = 2801
  • BrickletLEDStrip::CHIP_TYPE_WS2811 = 2811
  • BrickletLEDStrip::CHIP_TYPE_WS2812 = 2812

New in version 2.0.2 (Plugin).

int BrickletLEDStrip::getChipType()

Returns the currently used chip type as set by setChipType().

The following constants are available for this function:

  • BrickletLEDStrip::CHIP_TYPE_WS2801 = 2801
  • BrickletLEDStrip::CHIP_TYPE_WS2811 = 2811
  • BrickletLEDStrip::CHIP_TYPE_WS2812 = 2812

New in version 2.0.2 (Plugin).

Advanced Functions

array BrickletLEDStrip::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 BrickletLEDStrip::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.

See setResponseExpected() for the list of function ID constants available for this function.

void BrickletLEDStrip::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 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:

  • BrickletLEDStrip::FUNCTION_SET_RGB_VALUES = 1
  • BrickletLEDStrip::FUNCTION_SET_FRAME_DURATION = 3
  • BrickletLEDStrip::FUNCTION_SET_CLOCK_FREQUENCY = 7
  • BrickletLEDStrip::FUNCTION_SET_CHIP_TYPE = 9
void BrickletLEDStrip::setResponseExpectedAll(bool $response_expected)

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

array BrickletLEDStrip::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 BrickletLEDStrip::registerCallback(int $id, callable $callback, mixed $userData=NULL)

Registers a callback with ID $id to the callable $callback. The $userData will be given as a parameter of the callback.

The available IDs with corresponding function signatures are listed below.

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";
}

$led_strip->registerCallback(BrickletLEDStrip::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 BrickletLEDStrip::CALLBACK_FRAME_RENDERED
<?php   void callback(int $length [, mixed $userData])   ?>

This callback is triggered directly after a new frame is rendered.

You should send the data for the next frame directly after this callback was triggered.

For an explanation of the general approach see setRGBValues().

Constants

int BrickletLEDStrip::DEVICE_IDENTIFIER

This constant is used to identify a LED Strip Bricklet.

The getIdentity() function and the CALLBACK_ENUMERATE 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.