PHP - Load Cell Bricklet 2.0

This is the description of the PHP API bindings for the Load Cell Bricklet 2.0. General information and technical specifications for the Load Cell Bricklet 2.0 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)

 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
<?php

require_once('Tinkerforge/IPConnection.php');
require_once('Tinkerforge/BrickletLoadCellV2.php');

use Tinkerforge\IPConnection;
use Tinkerforge\BrickletLoadCellV2;

const HOST = 'localhost';
const PORT = 4223;
const UID = 'XYZ'; // Change XYZ to the UID of your Load Cell Bricklet 2.0

$ipcon = new IPConnection(); // Create IP connection
$lc = new BrickletLoadCellV2(UID, $ipcon); // Create device object

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

// Get current weight
$weight = $lc->getWeight();
echo "Weight: $weight g\n";

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

?>

Callback

Download (ExampleCallback.php)

 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
<?php

require_once('Tinkerforge/IPConnection.php');
require_once('Tinkerforge/BrickletLoadCellV2.php');

use Tinkerforge\IPConnection;
use Tinkerforge\BrickletLoadCellV2;

const HOST = 'localhost';
const PORT = 4223;
const UID = 'XYZ'; // Change XYZ to the UID of your Load Cell Bricklet 2.0

// Callback function for weight callback
function cb_weight($weight)
{
    echo "Weight: $weight g\n";
}

$ipcon = new IPConnection(); // Create IP connection
$lc = new BrickletLoadCellV2(UID, $ipcon); // Create device object

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

// Register weight callback to function cb_weight
$lc->registerCallback(BrickletLoadCellV2::CALLBACK_WEIGHT, 'cb_weight');

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

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

?>

Threshold

Download (ExampleThreshold.php)

 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
<?php

require_once('Tinkerforge/IPConnection.php');
require_once('Tinkerforge/BrickletLoadCellV2.php');

use Tinkerforge\IPConnection;
use Tinkerforge\BrickletLoadCellV2;

const HOST = 'localhost';
const PORT = 4223;
const UID = 'XYZ'; // Change XYZ to the UID of your Load Cell Bricklet 2.0

// Callback function for weight callback
function cb_weight($weight)
{
    echo "Weight: $weight g\n";
}

$ipcon = new IPConnection(); // Create IP connection
$lc = new BrickletLoadCellV2(UID, $ipcon); // Create device object

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

// Register weight callback to function cb_weight
$lc->registerCallback(BrickletLoadCellV2::CALLBACK_WEIGHT, 'cb_weight');

// Configure threshold for weight "greater than 200 g"
// with a debounce period of 1s (1000ms)
$lc->setWeightCallbackConfiguration(1000, FALSE, '>', 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 BrickletLoadCellV2(string $uid, IPConnection $ipcon)

Creates an object with the unique device ID $uid:

<?php   $load_cell_v2 = new BrickletLoadCellV2('YOUR_DEVICE_UID', $ipcon);   ?>

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

int BrickletLoadCellV2::getWeight()

Returns the currently measured weight in grams.

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

void BrickletLoadCellV2::setInfoLEDConfig(int $config)

Configures the info LED to be either turned off, turned on, or blink in heartbeat mode.

The following constants are available for this function:

  • BrickletLoadCellV2::INFO_LED_CONFIG_OFF = 0
  • BrickletLoadCellV2::INFO_LED_CONFIG_ON = 1
  • BrickletLoadCellV2::INFO_LED_CONFIG_SHOW_HEARTBEAT = 2
int BrickletLoadCellV2::getInfoLEDConfig()

Returns the LED configuration as set by setInfoLEDConfig()

The following constants are available for this function:

  • BrickletLoadCellV2::INFO_LED_CONFIG_OFF = 0
  • BrickletLoadCellV2::INFO_LED_CONFIG_ON = 1
  • BrickletLoadCellV2::INFO_LED_CONFIG_SHOW_HEARTBEAT = 2
void BrickletLoadCellV2::tare()

Sets the currently measured weight as tare weight.

Advanced Functions

void BrickletLoadCellV2::setMovingAverage(int $average)

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.

The range for the averaging is 1-100.

The default value is 4.

int BrickletLoadCellV2::getMovingAverage()

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

void BrickletLoadCellV2::calibrate(int $weight)

To calibrate your Load Cell Bricklet 2.0 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 in grams.

The calibration is saved in the flash 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.

void BrickletLoadCellV2::setConfiguration(int $rate, int $gain)

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 default rate is 10Hz and the default gain is 128x.

The following constants are available for this function:

  • BrickletLoadCellV2::RATE_10HZ = 0
  • BrickletLoadCellV2::RATE_80HZ = 1
  • BrickletLoadCellV2::GAIN_128X = 0
  • BrickletLoadCellV2::GAIN_64X = 1
  • BrickletLoadCellV2::GAIN_32X = 2
array BrickletLoadCellV2::getConfiguration()

Returns the configuration as set by setConfiguration().

The following constants are available for this function:

  • BrickletLoadCellV2::RATE_10HZ = 0
  • BrickletLoadCellV2::RATE_80HZ = 1
  • BrickletLoadCellV2::GAIN_128X = 0
  • BrickletLoadCellV2::GAIN_64X = 1
  • BrickletLoadCellV2::GAIN_32X = 2

The returned array has the keys rate and gain.

array BrickletLoadCellV2::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 BrickletLoadCellV2::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 BrickletLoadCellV2::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:

  • BrickletLoadCellV2::FUNCTION_SET_WEIGHT_CALLBACK_CONFIGURATION = 2
  • BrickletLoadCellV2::FUNCTION_SET_MOVING_AVERAGE = 5
  • BrickletLoadCellV2::FUNCTION_SET_INFO_LED_CONFIG = 7
  • BrickletLoadCellV2::FUNCTION_CALIBRATE = 9
  • BrickletLoadCellV2::FUNCTION_TARE = 10
  • BrickletLoadCellV2::FUNCTION_SET_CONFIGURATION = 11
  • BrickletLoadCellV2::FUNCTION_SET_WRITE_FIRMWARE_POINTER = 237
  • BrickletLoadCellV2::FUNCTION_SET_STATUS_LED_CONFIG = 239
  • BrickletLoadCellV2::FUNCTION_RESET = 243
  • BrickletLoadCellV2::FUNCTION_WRITE_UID = 248
void BrickletLoadCellV2::setResponseExpectedAll(bool $response_expected)

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

array BrickletLoadCellV2::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 BrickletLoadCellV2::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:

  • BrickletLoadCellV2::BOOTLOADER_MODE_BOOTLOADER = 0
  • BrickletLoadCellV2::BOOTLOADER_MODE_FIRMWARE = 1
  • BrickletLoadCellV2::BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
  • BrickletLoadCellV2::BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
  • BrickletLoadCellV2::BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4
  • BrickletLoadCellV2::BOOTLOADER_STATUS_OK = 0
  • BrickletLoadCellV2::BOOTLOADER_STATUS_INVALID_MODE = 1
  • BrickletLoadCellV2::BOOTLOADER_STATUS_NO_CHANGE = 2
  • BrickletLoadCellV2::BOOTLOADER_STATUS_ENTRY_FUNCTION_NOT_PRESENT = 3
  • BrickletLoadCellV2::BOOTLOADER_STATUS_DEVICE_IDENTIFIER_INCORRECT = 4
  • BrickletLoadCellV2::BOOTLOADER_STATUS_CRC_MISMATCH = 5
int BrickletLoadCellV2::getBootloaderMode()

Returns the current bootloader mode, see setBootloaderMode().

The following constants are available for this function:

  • BrickletLoadCellV2::BOOTLOADER_MODE_BOOTLOADER = 0
  • BrickletLoadCellV2::BOOTLOADER_MODE_FIRMWARE = 1
  • BrickletLoadCellV2::BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
  • BrickletLoadCellV2::BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
  • BrickletLoadCellV2::BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4
void BrickletLoadCellV2::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 BrickletLoadCellV2::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 BrickletLoadCellV2::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:

  • BrickletLoadCellV2::STATUS_LED_CONFIG_OFF = 0
  • BrickletLoadCellV2::STATUS_LED_CONFIG_ON = 1
  • BrickletLoadCellV2::STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
  • BrickletLoadCellV2::STATUS_LED_CONFIG_SHOW_STATUS = 3
int BrickletLoadCellV2::getStatusLEDConfig()

Returns the configuration as set by setStatusLEDConfig()

The following constants are available for this function:

  • BrickletLoadCellV2::STATUS_LED_CONFIG_OFF = 0
  • BrickletLoadCellV2::STATUS_LED_CONFIG_ON = 1
  • BrickletLoadCellV2::STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
  • BrickletLoadCellV2::STATUS_LED_CONFIG_SHOW_STATUS = 3
int BrickletLoadCellV2::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 BrickletLoadCellV2::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 BrickletLoadCellV2::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 BrickletLoadCellV2::readUID()

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

array BrickletLoadCellV2::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 BrickletLoadCellV2::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 BrickletLoadCellV2::setWeightCallbackConfiguration(int $period, bool $value_has_to_change, string $option, int $min, int $max)

The period in ms is the period with which the CALLBACK_WEIGHT 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_WEIGHT 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:

  • BrickletLoadCellV2::THRESHOLD_OPTION_OFF = 'x'
  • BrickletLoadCellV2::THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletLoadCellV2::THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletLoadCellV2::THRESHOLD_OPTION_SMALLER = '<'
  • BrickletLoadCellV2::THRESHOLD_OPTION_GREATER = '>'
array BrickletLoadCellV2::getWeightCallbackConfiguration()

Returns the callback configuration as set by setWeightCallbackConfiguration().

The following constants are available for this function:

  • BrickletLoadCellV2::THRESHOLD_OPTION_OFF = 'x'
  • BrickletLoadCellV2::THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletLoadCellV2::THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletLoadCellV2::THRESHOLD_OPTION_SMALLER = '<'
  • BrickletLoadCellV2::THRESHOLD_OPTION_GREATER = '>'

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

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";
}

$load_cell_v2->registerCallback(BrickletLoadCellV2::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 BrickletLoadCellV2::CALLBACK_WEIGHT
<?php   void callback(int $weight [, mixed $user_data])   ?>

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

The parameter is the same as getWeight().

Constants

int BrickletLoadCellV2::DEVICE_IDENTIFIER

This constant is used to identify a Load Cell Bricklet 2.0.

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 BrickletLoadCellV2::DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Load Cell Bricklet 2.0.