PHP - GPS Bricklet

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

use Tinkerforge\IPConnection;
use Tinkerforge\BrickletGPS;

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

$ipcon = new IPConnection(); // Create IP connection
$vc = new BrickletGPS($uid, ipcon); // Create device object

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

// Get current coordinates
$coords = $gps->getCoordinates();

echo "Latitude: " . $coords['latitude']/1000000.0 . "° " . $coords['ns'] . "\n";
echo "Longitude: " . $coords['longitude']/1000000.0 . "° " . $coords['ew'] . "\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/BrickletGPS.php');

use Tinkerforge\IPConnection;
use Tinkerforge\BrickletGPS;

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

// Callback function for current callback (parameter has unit mA)
function cb_coordinates($latitude, $ns, $longitude, $ew, $pdop, $hdop, $vdop, $epe)
{
    echo "Latitude: " . $latitude/1000000.0 . "° " . $ns . "\n";
    echo "Longitude: " . $longitude/1000000.0 . "° " . $ew . "\n";
}

$ipcon = new IPConnection(); // Create IP connection
$vc = new BrickletGPS($uid, ipcon); // Create device object

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

// Set Period for coordinates callback to 1s (1000ms)
// Note: The callback is only called every second if the 
//       coordinates have changed since the last call!
$vc->setCoordinatesCallbackPeriod(1000);

// Register coordinates callback to function cb_coordinates
$vc->registerCallback(BrickletGPS::CALLBACK_COORDINATES, 'cb_coordinates');

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 BrickletGPS(string $uid, IPConnection $ipcon)

Creates an object with the unique device ID $uid:

<?php   $gps = new BrickletGPS('YOUR_DEVICE_UID', $ipcon);   ?>

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

array BrickletGPS::getCoordinates()

Returns the GPS coordinates. Latitude and longitude are given in the DD.dddddd° format, the value 57123468 means 57.123468°. The parameter ns and ew are the cardinal directions for latitude and longitude. Possible values for ns and ew are 'N', 'S', 'E' and 'W' (north, south, east and west).

PDOP, HDOP and VDOP are the dilution of precision (DOP) values. They specify the additional multiplicative effect of GPS satellite geometry on GPS precision. See here for more information. The values are give in hundredths.

EPE is the "Estimated Position Error". The EPE is given in cm. This is not the absolute maximum error, it is the error with a specific confidence. See here for more information.

This data is only valid if there is currently a fix as indicated by getStatus().

The returned array has the keys latitude, ns, longitude, ew, pdop, hdop, vdop and epe.

array BrickletGPS::getStatus()

Returns the current fix status, the number of satellites that are in view and the number of satellites that are currently used.

Possible fix status values can be:

Value Description
1 No Fix, getCoordinates() and getAltitude() return invalid data
2 2D Fix, only getCoordinates() returns valid data
3 3D Fix, getCoordinates() and getAltitude() return valid data

There is also a blue LED on the Bricklet that indicates the fix status.

The following constants are available for this function:

  • BrickletGPS::FIX_NO_FIX = 1
  • BrickletGPS::FIX_2D_FIX = 2
  • BrickletGPS::FIX_3D_FIX = 3

The returned array has the keys fix, satellites_view and satellites_used.

array BrickletGPS::getAltitude()

Returns the current altitude and corresponding geoidal separation.

Both values are given in cm.

This data is only valid if there is currently a fix as indicated by getStatus().

The returned array has the keys altitude and geoidal_separation.

array BrickletGPS::getMotion()

Returns the current course and speed. Course is given in hundredths degree and speed is given in hundredths km/h. A course of 0° means the Bricklet is traveling north bound and 90° means it is traveling east bound.

Please note that this only returns useful values if an actual movement is present.

This data is only valid if there is currently a fix as indicated by getStatus().

The returned array has the keys course and speed.

array BrickletGPS::getDateTime()

Returns the current date and time. The date is given in the format ddmmyy and the time is given in the format hhmmss.sss. For example, 140713 means 14.05.13 as date and 195923568 means 19:59:23.568 as time.

The returned array has the keys date and time.

Advanced Functions

void BrickletGPS::restart(int $restart_type)

Restarts the GPS Bricklet, the following restart types are available:

Value Description
0 Hot start (use all available data in the NV store)
1 Warm start (don't use ephemeris at restart)
2 Cold start (don't use time, position, almanacs and ephemeris at restart)
3 Factory reset (clear all system/user configurations at restart)

The following constants are available for this function:

  • BrickletGPS::RESTART_TYPE_HOT_START = 0
  • BrickletGPS::RESTART_TYPE_WARM_START = 1
  • BrickletGPS::RESTART_TYPE_COLD_START = 2
  • BrickletGPS::RESTART_TYPE_FACTORY_RESET = 3
array BrickletGPS::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 BrickletGPS::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 BrickletGPS::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:

  • BrickletGPS::FUNCTION_RESTART = 6
  • BrickletGPS::FUNCTION_SET_COORDINATES_CALLBACK_PERIOD = 7
  • BrickletGPS::FUNCTION_SET_STATUS_CALLBACK_PERIOD = 9
  • BrickletGPS::FUNCTION_SET_ALTITUDE_CALLBACK_PERIOD = 11
  • BrickletGPS::FUNCTION_SET_MOTION_CALLBACK_PERIOD = 13
  • BrickletGPS::FUNCTION_SET_DATE_TIME_CALLBACK_PERIOD = 15
void BrickletGPS::setResponseExpectedAll(bool $response_expected)

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

array BrickletGPS::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 BrickletGPS::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.

void BrickletGPS::setCoordinatesCallbackPeriod(int $period)

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

CALLBACK_COORDINATES is only triggered if the coordinates changed since the last triggering.

The default value is 0.

int BrickletGPS::getCoordinatesCallbackPeriod()

Returns the period as set by setCoordinatesCallbackPeriod().

void BrickletGPS::setStatusCallbackPeriod(int $period)

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

CALLBACK_STATUS is only triggered if the status changed since the last triggering.

The default value is 0.

int BrickletGPS::getStatusCallbackPeriod()

Returns the period as set by setStatusCallbackPeriod().

void BrickletGPS::setAltitudeCallbackPeriod(int $period)

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

CALLBACK_ALTITUDE is only triggered if the altitude changed since the last triggering.

The default value is 0.

int BrickletGPS::getAltitudeCallbackPeriod()

Returns the period as set by setAltitudeCallbackPeriod().

void BrickletGPS::setMotionCallbackPeriod(int $period)

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

CALLBACK_MOTION is only triggered if the motion changed since the last triggering.

The default value is 0.

int BrickletGPS::getMotionCallbackPeriod()

Returns the period as set by setMotionCallbackPeriod().

void BrickletGPS::setDateTimeCallbackPeriod(int $period)

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

CALLBACK_DATE_TIME is only triggered if the date or time changed since the last triggering.

The default value is 0.

int BrickletGPS::getDateTimeCallbackPeriod()

Returns the period as set by setDateTimeCallbackPeriod().

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";
}

$gps->registerCallback(BrickletGPS::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 BrickletGPS::CALLBACK_COORDINATES
<?php   void callback(int $latitude, string $ns, int $longitude, string $ew, int $pdop, int $hdop, int $vdop, int $epe [, mixed $userData])   ?>

This callback is triggered periodically with the period that is set by setCoordinatesCallbackPeriod(). The parameters are the same as for getCoordinates().

CALLBACK_COORDINATES is only triggered if the coordinates changed since the last triggering and if there is currently a fix as indicated by getStatus().

int BrickletGPS::CALLBACK_STATUS
<?php   void callback(int $fix, int $satellites_view, int $satellites_used [, mixed $userData])   ?>

This callback is triggered periodically with the period that is set by setStatusCallbackPeriod(). The parameters are the same as for getStatus().

CALLBACK_STATUS is only triggered if the status changed since the last triggering.

The following constants are available for this function:

  • BrickletGPS::FIX_NO_FIX = 1
  • BrickletGPS::FIX_2D_FIX = 2
  • BrickletGPS::FIX_3D_FIX = 3
int BrickletGPS::CALLBACK_ALTITUDE
<?php   void callback(int $altitude, int $geoidal_separation [, mixed $userData])   ?>

This callback is triggered periodically with the period that is set by setAltitudeCallbackPeriod(). The parameters are the same as for getAltitude().

CALLBACK_ALTITUDE is only triggered if the altitude changed since the last triggering and if there is currently a fix as indicated by getStatus().

int BrickletGPS::CALLBACK_MOTION
<?php   void callback(int $course, int $speed [, mixed $userData])   ?>

This callback is triggered periodically with the period that is set by setMotionCallbackPeriod(). The parameters are the same as for getMotion().

CALLBACK_MOTION is only triggered if the motion changed since the last triggering and if there is currently a fix as indicated by getStatus().

int BrickletGPS::CALLBACK_DATE_TIME
<?php   void callback(int $date, int $time [, mixed $userData])   ?>

This callback is triggered periodically with the period that is set by setDateTimeCallbackPeriod(). The parameters are the same as for getDateTime().

CALLBACK_DATE_TIME is only triggered if the date or time changed since the last triggering.

Constants

int BrickletGPS::DEVICE_IDENTIFIER

This constant is used to identify a GPS 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.

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