Software / API Bindings / C/C++ / API Reference and Examples / Bricklets / Line Bricklet

C/C++ - Line Bricklet¶

This is the description of the C/C++ API bindings for the Line Bricklet. General information and technical specifications for the Line Bricklet are summarized in its hardware description.

An installation guide for the C/C++ API bindings is part of their general description.

Examples¶

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

Simple¶

Download (example_simple.c)

#include <stdio.h>

#include "ip_connection.h"
#include "bricklet_line.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XYZ" // Change XYZ to the UID of your Line Bricklet

int main(void) {
    // Create IP connection
    IPConnection ipcon;
    ipcon_create(&ipcon);

    // Create device object
    Line l;
    line_create(&l, UID, &ipcon);

    // Connect to brickd
    if(ipcon_connect(&ipcon, HOST, PORT) < 0) {
        fprintf(stderr, "Could not connect\n");
        return 1;
    }
    // Don't use device before ipcon is connected

    // Get current reflectivity
    uint16_t reflectivity;
    if(line_get_reflectivity(&l, &reflectivity) < 0) {
        fprintf(stderr, "Could not get reflectivity, probably timeout\n");
        return 1;
    }

    printf("Reflectivity: %u\n", reflectivity);

    printf("Press key to exit\n");
    getchar();
    line_destroy(&l);
    ipcon_destroy(&ipcon); // Calls ipcon_disconnect internally
    return 0;
}

Callback¶

Download (example_callback.c)

#include <stdio.h>

#include "ip_connection.h"
#include "bricklet_line.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XYZ" // Change XYZ to the UID of your Line Bricklet

// Callback function for reflectivity callback
void cb_reflectivity(uint16_t reflectivity, void *user_data) {
    (void)user_data; // avoid unused parameter warning

    printf("Reflectivity: %u\n", reflectivity);
}

int main(void) {
    // Create IP connection
    IPConnection ipcon;
    ipcon_create(&ipcon);

    // Create device object
    Line l;
    line_create(&l, UID, &ipcon);

    // Connect to brickd
    if(ipcon_connect(&ipcon, HOST, PORT) < 0) {
        fprintf(stderr, "Could not connect\n");
        return 1;
    }
    // Don't use device before ipcon is connected

    // Register reflectivity callback to function cb_reflectivity
    line_register_callback(&l,
                           LINE_CALLBACK_REFLECTIVITY,
                           (void (*)(void))cb_reflectivity,
                           NULL);

    // Set period for reflectivity callback to 1s (1000ms)
    // Note: The reflectivity callback is only called every second
    //       if the reflectivity has changed since the last call!
    line_set_reflectivity_callback_period(&l, 1000);

    printf("Press key to exit\n");
    getchar();
    line_destroy(&l);
    ipcon_destroy(&ipcon); // Calls ipcon_disconnect internally
    return 0;
}

Threshold¶

Download (example_threshold.c)

#include <stdio.h>

#include "ip_connection.h"
#include "bricklet_line.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XYZ" // Change XYZ to the UID of your Line Bricklet

// Callback function for reflectivity reached callback
void cb_reflectivity_reached(uint16_t reflectivity, void *user_data) {
    (void)user_data; // avoid unused parameter warning

    printf("Reflectivity: %u\n", reflectivity);
}

int main(void) {
    // Create IP connection
    IPConnection ipcon;
    ipcon_create(&ipcon);

    // Create device object
    Line l;
    line_create(&l, UID, &ipcon);

    // Connect to brickd
    if(ipcon_connect(&ipcon, HOST, PORT) < 0) {
        fprintf(stderr, "Could not connect\n");
        return 1;
    }
    // Don't use device before ipcon is connected

    // Get threshold callbacks with a debounce time of 1 second (1000ms)
    line_set_debounce_period(&l, 1000);

    // Register reflectivity reached callback to function cb_reflectivity_reached
    line_register_callback(&l,
                           LINE_CALLBACK_REFLECTIVITY_REACHED,
                           (void (*)(void))cb_reflectivity_reached,
                           NULL);

    // Configure threshold for reflectivity "greater than 2000"
    line_set_reflectivity_callback_threshold(&l, '>', 2000, 0);

    printf("Press key to exit\n");
    getchar();
    line_destroy(&l);
    ipcon_destroy(&ipcon); // Calls ipcon_disconnect internally
    return 0;
}

API¶

Most functions of the C/C++ bindings return an error code (e_code). Data returned from the device, when a getter is called, is handled via output parameters. These parameters are labeled with the ret_ prefix.

Possible error codes are:

E_OK = 0
E_TIMEOUT = -1
E_NO_STREAM_SOCKET = -2
E_HOSTNAME_INVALID = -3
E_NO_CONNECT = -4
E_NO_THREAD = -5
E_NOT_ADDED = -6 (unused since C/C++ bindings version 2.0.0)
E_ALREADY_CONNECTED = -7
E_NOT_CONNECTED = -8
E_INVALID_PARAMETER = -9
E_NOT_SUPPORTED = -10
E_UNKNOWN_ERROR_CODE = -11
E_STREAM_OUT_OF_SYNC = -12
E_INVALID_UID = -13
E_NON_ASCII_CHAR_IN_SECRET = -14
E_WRONG_DEVICE_TYPE = -15
E_DEVICE_REPLACED = -16
E_WRONG_RESPONSE_LENGTH = -17

as defined in ip_connection.h.

All functions listed below are thread-safe.

Basic Functions¶

void line_create(Line *line, const char *uid, IPConnection *ipcon)¶

Parameters:	line – Type: Line * uid – Type: const char * ipcon – Type: IPConnection *

Creates the device object line with the unique device ID uid and adds it to the IPConnection ipcon:

Line line;
line_create(&line, "YOUR_DEVICE_UID", &ipcon);

This device object can be used after the IP connection has been connected.

void line_destroy(Line *line)¶

Parameters:	line – Type: Line *

Removes the device object line from its IPConnection and destroys it. The device object cannot be used anymore afterwards.

int line_get_reflectivity(Line *line, uint16_t *ret_reflectivity)¶

Parameters:	line – Type: Line *
Output Parameters:	ret_reflectivity – Type: uint16_t, Range: [0 to 2¹² - 1]
Returns:	e_code – Type: int

Returns the currently measured reflectivity. The reflectivity is a value between 0 (not reflective) and 4095 (very reflective).

Usually black has a low reflectivity while white has a high reflectivity.

If you want to get the reflectivity periodically, it is recommended to use the LINE_CALLBACK_REFLECTIVITY callback and set the period with line_set_reflectivity_callback_period().

Advanced Functions¶

int line_get_identity(Line *line, char ret_uid[8], char ret_connected_uid[8], char *ret_position, uint8_t ret_hardware_version[3], uint8_t ret_firmware_version[3], uint16_t *ret_device_identifier)¶

Parameters:	line – Type: Line *
Output Parameters:	ret_uid – Type: char[8] ret_connected_uid – Type: char[8] ret_position – Type: char, Range: ['a' to 'h', 'z'] ret_hardware_version – Type: uint8_t[3] 0: major – Type: uint8_t, Range: [0 to 255] 1: minor – Type: uint8_t, Range: [0 to 255] 2: revision – Type: uint8_t, Range: [0 to 255] ret_firmware_version – Type: uint8_t[3] 0: major – Type: uint8_t, Range: [0 to 255] 1: minor – Type: uint8_t, Range: [0 to 255] 2: revision – Type: uint8_t, Range: [0 to 255] ret_device_identifier – Type: uint16_t, Range: [0 to 2¹⁶ - 1]
Returns:	e_code – Type: int

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', 'd', 'e', 'f', 'g' or 'h' (Bricklet Port). A Bricklet connected to an Isolator Bricklet is always at position 'z'.

The device identifier numbers can be found here. There is also a constant for the device identifier of this Bricklet.

Callback Configuration Functions¶

void line_register_callback(Line *line, int16_t callback_id, void (*function)(void), void *user_data)¶

Parameters:	line – Type: Line * callback_id – Type: int16_t function – Type: void ()(void) user_data* – Type: void *

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

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

int line_set_reflectivity_callback_period(Line *line, uint32_t period)¶

Parameters:	line – Type: Line * period – Type: uint32_t, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Returns:	e_code – Type: int

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

The LINE_CALLBACK_REFLECTIVITY callback is only triggered if the reflectivity has changed since the last triggering.

int line_get_reflectivity_callback_period(Line *line, uint32_t *ret_period)¶

Parameters:	line – Type: Line *
Output Parameters:	ret_period – Type: uint32_t, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Returns:	e_code – Type: int

Returns the period as set by line_set_reflectivity_callback_period().

int line_set_reflectivity_callback_threshold(Line *line, char option, uint16_t min, uint16_t max)¶

Parameters:	line – Type: Line * option – Type: char, Range: See constants, Default: 'x' min – Type: uint16_t, Range: [0 to 2¹⁶ - 1], Default: 0 max – Type: uint16_t, Range: [0 to 2¹⁶ - 1], Default: 0
Returns:	e_code – Type: int

Sets the thresholds for the LINE_CALLBACK_REFLECTIVITY_REACHED callback.

The following options are possible:

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

The following constants are available for this function:

For option:

LINE_THRESHOLD_OPTION_OFF = 'x'
LINE_THRESHOLD_OPTION_OUTSIDE = 'o'
LINE_THRESHOLD_OPTION_INSIDE = 'i'
LINE_THRESHOLD_OPTION_SMALLER = '<'
LINE_THRESHOLD_OPTION_GREATER = '>'

int line_get_reflectivity_callback_threshold(Line *line, char *ret_option, uint16_t *ret_min, uint16_t *ret_max)¶

Parameters:	line – Type: Line *
Output Parameters:	ret_option – Type: char, Range: See constants, Default: 'x' ret_min – Type: uint16_t, Range: [0 to 2¹⁶ - 1], Default: 0 ret_max – Type: uint16_t, Range: [0 to 2¹⁶ - 1], Default: 0
Returns:	e_code – Type: int

Returns the threshold as set by line_set_reflectivity_callback_threshold().

The following constants are available for this function:

For ret_option:

LINE_THRESHOLD_OPTION_OFF = 'x'
LINE_THRESHOLD_OPTION_OUTSIDE = 'o'
LINE_THRESHOLD_OPTION_INSIDE = 'i'
LINE_THRESHOLD_OPTION_SMALLER = '<'
LINE_THRESHOLD_OPTION_GREATER = '>'

int line_set_debounce_period(Line *line, uint32_t debounce)¶

Parameters:	line – Type: Line * debounce – Type: uint32_t, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 100
Returns:	e_code – Type: int

Sets the period with which the threshold callback

LINE_CALLBACK_REFLECTIVITY_REACHED

is triggered, if the threshold

line_set_reflectivity_callback_threshold()

keeps being reached.

int line_get_debounce_period(Line *line, uint32_t *ret_debounce)¶

Parameters:	line – Type: Line *
Output Parameters:	ret_debounce – Type: uint32_t, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 100
Returns:	e_code – Type: int

Returns the debounce period as set by line_set_debounce_period().

Callbacks¶

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the line_register_callback() function:

void my_callback(int value, void *user_data) {
    printf("Value: %d\n", value);
}

line_register_callback(&line,
                       LINE_CALLBACK_EXAMPLE,
                       (void (*)(void))my_callback,
                       NULL);

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.

LINE_CALLBACK_REFLECTIVITY¶

void callback(uint16_t reflectivity, void *user_data)

Callback Parameters:	reflectivity – Type: uint16_t, Range: [0 to 2¹² - 1] user_data – Type: void *

This callback is triggered periodically with the period that is set by line_set_reflectivity_callback_period(). The parameter is the reflectivity of the sensor.

The LINE_CALLBACK_REFLECTIVITY callback is only triggered if the reflectivity has changed since the last triggering.

LINE_CALLBACK_REFLECTIVITY_REACHED¶

void callback(uint16_t reflectivity, void *user_data)

Callback Parameters:	reflectivity – Type: uint16_t, Range: [0 to 2¹² - 1] user_data – Type: void *

This callback is triggered when the threshold as set by line_set_reflectivity_callback_threshold() is reached. The parameter is the reflectivity of the sensor.

If the threshold keeps being reached, the callback is triggered periodically with the period as set by line_set_debounce_period().

Virtual Functions¶

Virtual functions don't communicate with the device itself, but operate only on the API bindings device object. They can be called without the corresponding IP Connection object being connected.

int line_get_api_version(Line *line, uint8_t ret_api_version[3])¶

Parameters:	line – Type: Line *
Output Parameters:	ret_api_version – Type: uint8_t[3] 0: major – Type: uint8_t, Range: [0 to 255] 1: minor – Type: uint8_t, Range: [0 to 255] 2: revision – Type: uint8_t, Range: [0 to 255]
Returns:	e_code – Type: int

Returns the version of the API definition 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.

int line_get_response_expected(Line *line, uint8_t function_id, bool *ret_response_expected)¶

Parameters:	line – Type: Line * function_id – Type: uint8_t, Range: See constants
Output Parameters:	ret_response_expected – Type: bool
Returns:	e_code – Type: int

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 line_set_response_expected(). 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 sent and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

For function_id:

LINE_FUNCTION_SET_REFLECTIVITY_CALLBACK_PERIOD = 2
LINE_FUNCTION_SET_REFLECTIVITY_CALLBACK_THRESHOLD = 4
LINE_FUNCTION_SET_DEBOUNCE_PERIOD = 6

int line_set_response_expected(Line *line, uint8_t function_id, bool response_expected)¶

Parameters:	line – Type: Line * function_id – Type: uint8_t, Range: See constants response_expected – Type: bool
Returns:	e_code – Type: int

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.

The following constants are available for this function:

For function_id:

LINE_FUNCTION_SET_REFLECTIVITY_CALLBACK_PERIOD = 2
LINE_FUNCTION_SET_REFLECTIVITY_CALLBACK_THRESHOLD = 4
LINE_FUNCTION_SET_DEBOUNCE_PERIOD = 6

int line_set_response_expected_all(Line *line, bool response_expected)¶

Parameters:	line – Type: Line * response_expected – Type: bool
Returns:	e_code – Type: int

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

Constants¶

LINE_DEVICE_IDENTIFIER¶

This constant is used to identify a Line Bricklet.

The line_get_identity() function and the IPCON_CALLBACK_ENUMERATE callback of the IP Connection have a device_identifier parameter to specify the Brick's or Bricklet's type.

LINE_DEVICE_DISPLAY_NAME¶: This constant represents the human readable name of a Line Bricklet.