PHP - Sound Pressure Level Bricklet

This is the description of the PHP API bindings for the Sound Pressure Level Bricklet. General information and technical specifications for the Sound Pressure Level 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/BrickletSoundPressureLevel.php');

use Tinkerforge\IPConnection;
use Tinkerforge\BrickletSoundPressureLevel;

const HOST = 'localhost';
const PORT = 4223;
const UID = 'XYZ'; // Change XYZ to the UID of your Sound Pressure Level Bricklet

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

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

// Get current decibel
$decibel = $spl->getDecibel();
echo "Decibel: " . $decibel/10.0 . " dB(A)\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/BrickletSoundPressureLevel.php');

use Tinkerforge\IPConnection;
use Tinkerforge\BrickletSoundPressureLevel;

const HOST = 'localhost';
const PORT = 4223;
const UID = 'XYZ'; // Change XYZ to the UID of your Sound Pressure Level Bricklet

// Callback function for decibel callback
function cb_decibel($decibel)
{
    echo "Decibel: " . $decibel/10.0 . " dB(A)\n";
}

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

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

// Register decibel callback to function cb_decibel
$spl->registerCallback(BrickletSoundPressureLevel::CALLBACK_DECIBEL, 'cb_decibel');

// Set period for decibel callback to 1s (1000ms) without a threshold
$spl->setDecibelCallbackConfiguration(1000, FALSE, 'x', 0, 0);

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/BrickletSoundPressureLevel.php');

use Tinkerforge\IPConnection;
use Tinkerforge\BrickletSoundPressureLevel;

const HOST = 'localhost';
const PORT = 4223;
const UID = 'XYZ'; // Change XYZ to the UID of your Sound Pressure Level Bricklet

// Callback function for decibel callback
function cb_decibel($decibel)
{
    echo "Decibel: " . $decibel/10.0 . " dB(A)\n";
}

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

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

// Register decibel callback to function cb_decibel
$spl->registerCallback(BrickletSoundPressureLevel::CALLBACK_DECIBEL, 'cb_decibel');

// Configure threshold for decibel "greater than 60 dB(A)"
// with a debounce period of 1s (1000ms)
$spl->setDecibelCallbackConfiguration(1000, FALSE, '>', 60*10, 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 BrickletSoundPressureLevel(string $uid, IPConnection $ipcon)

Creates an object with the unique device ID $uid:

<?php   $sound_pressure_level = new BrickletSoundPressureLevel('YOUR_DEVICE_UID', $ipcon);   ?>

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

int BrickletSoundPressureLevel::getDecibel()

Returns the measured sound pressure in decibels. The values are given in dB/10 (tenths dB).

The Bricklet supports the weighting standards dB(A), dB(B), dB(C), dB(D), dB(Z) and ITU-R 468. You can configure the weighting with setConfiguration().

By default dB(A) will be used.

If you want to get the value periodically, it is recommended to use the CALLBACK_DECIBEL callback. You can set the callback configuration with setDecibelCallbackConfiguration().

array BrickletSoundPressureLevel::getSpectrum()

Returns the frequency spectrum. The length of the spectrum is between 512 (FFT size 1024) and 64 (FFT size 128). See setConfiguration().

Each array element is one bin of the FFT. The first bin is always the DC offset and the other bins have a size between 40Hz (FFT size 1024) and 320Hz (FFT size 128).

In sum the frequency of the spectrum always has a range from 0 to 20480Hz (the FFT is applied to samples with a frequency of 40960Hz).

The returned data is already equalized, which means that the microphone frequency response is compensated and the weighting function is applied (see setConfiguration() for the available weighting standards). Use dB(Z) if you need the unaltered spectrum.

The values are not in dB form yet. If you want a proper dB scale of the spectrum you have to apply the formula f(x) = 20*log10(max(1, x/sqrt(2))) on each value.

void BrickletSoundPressureLevel::setConfiguration(int $fft_size, int $weighting)

Sets the Sound Pressure Level Bricklet configuration.

With different FFT sizes the Bricklet has a different amount of samples per second and the size of the FFT bins changes. The higher the FFT size the more precise is the result of the dB(X) calculation.

Available FFT sizes are:

  • 1024: 512 bins, 10 samples per second, each bin has size 40Hz
  • 512: 256 bins, 20 samples per second, each bin has size 80Hz
  • 256: 128 bins, 40 samples per second, each bin has size 160Hz
  • 128: 64 bins, 80 samples per second, each bin has size 320Hz

The Bricklet supports different weighting functions. You can choose between dB(A), dB(B), dB(C), dB(D), dB(Z) and ITU-R 468.

dB(A/B/C/D) are the standard dB weighting curves. dB(A) is often used to measure volumes at concerts etc. dB(Z) has a flat response, no weighting is applied. ITU-R 468 is an ITU weighting standard mostly used in the UK and Europe.

The defaults are FFT size 1024 and weighting standard dB(A).

The following constants are available for this function:

  • BrickletSoundPressureLevel::FFT_SIZE_128 = 0
  • BrickletSoundPressureLevel::FFT_SIZE_256 = 1
  • BrickletSoundPressureLevel::FFT_SIZE_512 = 2
  • BrickletSoundPressureLevel::FFT_SIZE_1024 = 3
  • BrickletSoundPressureLevel::WEIGHTING_A = 0
  • BrickletSoundPressureLevel::WEIGHTING_B = 1
  • BrickletSoundPressureLevel::WEIGHTING_C = 2
  • BrickletSoundPressureLevel::WEIGHTING_D = 3
  • BrickletSoundPressureLevel::WEIGHTING_Z = 4
  • BrickletSoundPressureLevel::WEIGHTING_ITU_R_468 = 5
array BrickletSoundPressureLevel::getConfiguration()

Returns the configuration as set by setConfiguration().

The following constants are available for this function:

  • BrickletSoundPressureLevel::FFT_SIZE_128 = 0
  • BrickletSoundPressureLevel::FFT_SIZE_256 = 1
  • BrickletSoundPressureLevel::FFT_SIZE_512 = 2
  • BrickletSoundPressureLevel::FFT_SIZE_1024 = 3
  • BrickletSoundPressureLevel::WEIGHTING_A = 0
  • BrickletSoundPressureLevel::WEIGHTING_B = 1
  • BrickletSoundPressureLevel::WEIGHTING_C = 2
  • BrickletSoundPressureLevel::WEIGHTING_D = 3
  • BrickletSoundPressureLevel::WEIGHTING_Z = 4
  • BrickletSoundPressureLevel::WEIGHTING_ITU_R_468 = 5

The returned array has the keys fft_size and weighting.

Advanced Functions

array BrickletSoundPressureLevel::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 BrickletSoundPressureLevel::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 BrickletSoundPressureLevel::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 function ID constants are available for this function:

  • BrickletSoundPressureLevel::FUNCTION_SET_DECIBEL_CALLBACK_CONFIGURATION = 2
  • BrickletSoundPressureLevel::FUNCTION_SET_SPECTRUM_CALLBACK_CONFIGURATION = 6
  • BrickletSoundPressureLevel::FUNCTION_SET_CONFIGURATION = 9
  • BrickletSoundPressureLevel::FUNCTION_SET_WRITE_FIRMWARE_POINTER = 237
  • BrickletSoundPressureLevel::FUNCTION_SET_STATUS_LED_CONFIG = 239
  • BrickletSoundPressureLevel::FUNCTION_RESET = 243
  • BrickletSoundPressureLevel::FUNCTION_WRITE_UID = 248
void BrickletSoundPressureLevel::setResponseExpectedAll(bool $response_expected)

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

array BrickletSoundPressureLevel::getSPITFPErrorCount()

Returns the error count for the communication between Brick and Bricklet.

The errors are divided into

  • ACK checksum errors,
  • message checksum errors,
  • framing errors and
  • overflow errors.

The errors counts are for errors that occur on the Bricklet side. All Bricks have a similar function that returns the errors on the Brick side.

The returned array has the keys error_count_ack_checksum, error_count_message_checksum, error_count_frame and error_count_overflow.

int BrickletSoundPressureLevel::setBootloaderMode(int $mode)

Sets the bootloader mode and returns the status after the requested mode change was instigated.

You can change from bootloader mode to firmware mode and vice versa. A change from bootloader mode to firmware mode will only take place if the entry function, device identifier and CRC are present and correct.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

The following constants are available for this function:

  • BrickletSoundPressureLevel::BOOTLOADER_MODE_BOOTLOADER = 0
  • BrickletSoundPressureLevel::BOOTLOADER_MODE_FIRMWARE = 1
  • BrickletSoundPressureLevel::BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
  • BrickletSoundPressureLevel::BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
  • BrickletSoundPressureLevel::BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4
  • BrickletSoundPressureLevel::BOOTLOADER_STATUS_OK = 0
  • BrickletSoundPressureLevel::BOOTLOADER_STATUS_INVALID_MODE = 1
  • BrickletSoundPressureLevel::BOOTLOADER_STATUS_NO_CHANGE = 2
  • BrickletSoundPressureLevel::BOOTLOADER_STATUS_ENTRY_FUNCTION_NOT_PRESENT = 3
  • BrickletSoundPressureLevel::BOOTLOADER_STATUS_DEVICE_IDENTIFIER_INCORRECT = 4
  • BrickletSoundPressureLevel::BOOTLOADER_STATUS_CRC_MISMATCH = 5
int BrickletSoundPressureLevel::getBootloaderMode()

Returns the current bootloader mode, see setBootloaderMode().

The following constants are available for this function:

  • BrickletSoundPressureLevel::BOOTLOADER_MODE_BOOTLOADER = 0
  • BrickletSoundPressureLevel::BOOTLOADER_MODE_FIRMWARE = 1
  • BrickletSoundPressureLevel::BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
  • BrickletSoundPressureLevel::BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
  • BrickletSoundPressureLevel::BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4
void BrickletSoundPressureLevel::setWriteFirmwarePointer(int $pointer)

Sets the firmware pointer for writeFirmware(). The pointer has to be increased by chunks of size 64. The data is written to flash every 4 chunks (which equals to one page of size 256).

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

int BrickletSoundPressureLevel::writeFirmware(array $data)

Writes 64 Bytes of firmware at the position as written by setWriteFirmwarePointer() before. The firmware is written to flash every 4 chunks.

You can only write firmware in bootloader mode.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

void BrickletSoundPressureLevel::setStatusLEDConfig(int $config)

Sets the status LED configuration. By default the LED shows communication traffic between Brick and Bricklet, it flickers once for every 10 received data packets.

You can also turn the LED permanently on/off or show a heartbeat.

If the Bricklet is in bootloader mode, the LED is will show heartbeat by default.

The following constants are available for this function:

  • BrickletSoundPressureLevel::STATUS_LED_CONFIG_OFF = 0
  • BrickletSoundPressureLevel::STATUS_LED_CONFIG_ON = 1
  • BrickletSoundPressureLevel::STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
  • BrickletSoundPressureLevel::STATUS_LED_CONFIG_SHOW_STATUS = 3
int BrickletSoundPressureLevel::getStatusLEDConfig()

Returns the configuration as set by setStatusLEDConfig()

The following constants are available for this function:

  • BrickletSoundPressureLevel::STATUS_LED_CONFIG_OFF = 0
  • BrickletSoundPressureLevel::STATUS_LED_CONFIG_ON = 1
  • BrickletSoundPressureLevel::STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
  • BrickletSoundPressureLevel::STATUS_LED_CONFIG_SHOW_STATUS = 3
int BrickletSoundPressureLevel::getChipTemperature()

Returns the temperature in °C as measured inside the microcontroller. The value returned is not the ambient temperature!

The temperature is only proportional to the real temperature and it has bad accuracy. Practically it is only useful as an indicator for temperature changes.

void BrickletSoundPressureLevel::reset()

Calling this function will reset the Bricklet. All configurations will be lost.

After a reset you have to create new device objects, calling functions on the existing ones will result in undefined behavior!

void BrickletSoundPressureLevel::writeUID(int $uid)

Writes a new UID into flash. If you want to set a new UID you have to decode the Base58 encoded UID string into an integer first.

We recommend that you use Brick Viewer to change the UID.

int BrickletSoundPressureLevel::readUID()

Returns the current UID as an integer. Encode as Base58 to get the usual string version.

array BrickletSoundPressureLevel::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 BrickletSoundPressureLevel::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 BrickletSoundPressureLevel::setDecibelCallbackConfiguration(int $period, bool $value_has_to_change, string $option, int $min, int $max)

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

If the value has to change-parameter is set to true, the callback is only triggered after the value has changed. If the value didn't change within the period, the callback is triggered immediately on change.

If it is set to false, the callback is continuously triggered with the period, independent of the value.

It is furthermore possible to constrain the callback with thresholds.

The option-parameter together with min/max sets a threshold for the CALLBACK_DECIBEL callback.

The following options are possible:

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

If the option is set to 'x' (threshold turned off) the callback is triggered with the fixed period.

The default value is (0, false, 'x', 0, 0).

The following constants are available for this function:

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

Returns the callback configuration as set by setDecibelCallbackConfiguration().

The following constants are available for this function:

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

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

void BrickletSoundPressureLevel::setSpectrumCallbackConfiguration(int $period)

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

Every new measured spectrum will be send at most once. Set the period to 1 to make sure that you get every spectrum.

The default value is 0.

int BrickletSoundPressureLevel::getSpectrumCallbackConfiguration()

Returns the callback configuration as set by getSpectrumCallbackConfiguration().

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";
}

$sound_pressure_level->registerCallback(BrickletSoundPressureLevel::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 BrickletSoundPressureLevel::CALLBACK_DECIBEL
<?php   void callback(int $decibel [, mixed $user_data])   ?>

This callback is triggered periodically according to the configuration set by setDecibelCallbackConfiguration().

The parameter is the same as getDecibel().

int BrickletSoundPressureLevel::CALLBACK_SPECTRUM
<?php   void callback(array $spectrum [, mixed $user_data])   ?>

This callback is triggered periodically according to the configuration set by setSpectrumCallbackConfiguration().

The parameter is the same as getSpectrum().

Constants

int BrickletSoundPressureLevel::DEVICE_IDENTIFIER

This constant is used to identify a Sound Pressure Level 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.

string BrickletSoundPressureLevel::DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Sound Pressure Level Bricklet.