C/C++ - Dual Button Bricklet

This is the description of the C/C++ API bindings for the Dual Button Bricklet. General information and technical specifications for the Dual Button 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).

Callback

Download (example_callback.c)

 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
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
#include <stdio.h>

#include "ip_connection.h"
#include "bricklet_dual_button.h"

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

// Callback function for state changed callback
void cb_state_changed(uint8_t button_l, uint8_t button_r, uint8_t led_l, uint8_t led_r,
                      void *user_data) {
    (void)led_l; (void)led_r; (void)user_data; // avoid unused parameter warning

    if(button_l == DUAL_BUTTON_BUTTON_STATE_PRESSED) {
        printf("Left Button: Pressed\n");
    } else if(button_l == DUAL_BUTTON_BUTTON_STATE_RELEASED) {
        printf("Left Button: Released\n");
    }

    if(button_r == DUAL_BUTTON_BUTTON_STATE_PRESSED) {
        printf("Right Button: Pressed\n");
    } else if(button_r == DUAL_BUTTON_BUTTON_STATE_RELEASED) {
        printf("Right Button: Released\n");
    }

    printf("\n");
}

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

    // Create device object
    DualButton db;
    dual_button_create(&db, 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 state changed callback to function cb_state_changed
    dual_button_register_callback(&db,
                                  DUAL_BUTTON_CALLBACK_STATE_CHANGED,
                                  (void *)cb_state_changed,
                                  NULL);

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

API

Every function of the C/C++ bindings returns an integer which describes an error code. Data returned from the device, when a getter is called, is handled via call by reference. 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 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

as defined in ip_connection.h.

All functions listed below are thread-safe.

Basic Functions

void dual_button_create(DualButton *dual_button, const char *uid, IPConnection *ipcon)

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

DualButton dual_button;
dual_button_create(&dual_button, "YOUR_DEVICE_UID", &ipcon);

This device object can be used after the IP connection has been connected (see examples above).

void dual_button_destroy(DualButton *dual_button)

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

int dual_button_set_led_state(DualButton *dual_button, uint8_t led_l, uint8_t led_r)

Sets the state of the LEDs. Possible states are:

  • 0 = AutoToggleOn: Enables auto toggle with initially enabled LED.
  • 1 = AutoToggleOff: Activates auto toggle with initially disabled LED.
  • 2 = On: Enables LED (auto toggle is disabled).
  • 3 = Off: Disables LED (auto toggle is disabled).

In auto toggle mode the LED is toggled automatically at each press of a button.

If you just want to set one of the LEDs and don't know the current state of the other LED, you can get the state with dual_button_get_led_state() or you can use dual_button_set_selected_led_state().

The default value is (1, 1).

The following defines are available for this function:

  • DUAL_BUTTON_LED_STATE_AUTO_TOGGLE_ON = 0
  • DUAL_BUTTON_LED_STATE_AUTO_TOGGLE_OFF = 1
  • DUAL_BUTTON_LED_STATE_ON = 2
  • DUAL_BUTTON_LED_STATE_OFF = 3
int dual_button_get_led_state(DualButton *dual_button, uint8_t *ret_led_l, uint8_t *ret_led_r)

Returns the current state of the LEDs, as set by dual_button_set_led_state().

The following defines are available for this function:

  • DUAL_BUTTON_LED_STATE_AUTO_TOGGLE_ON = 0
  • DUAL_BUTTON_LED_STATE_AUTO_TOGGLE_OFF = 1
  • DUAL_BUTTON_LED_STATE_ON = 2
  • DUAL_BUTTON_LED_STATE_OFF = 3
int dual_button_get_button_state(DualButton *dual_button, uint8_t *ret_button_l, uint8_t *ret_button_r)

Returns the current state for both buttons. Possible states are:

  • 0 = pressed
  • 1 = released

The following defines are available for this function:

  • DUAL_BUTTON_BUTTON_STATE_PRESSED = 0
  • DUAL_BUTTON_BUTTON_STATE_RELEASED = 1

Advanced Functions

int dual_button_set_selected_led_state(DualButton *dual_button, uint8_t led, uint8_t state)

Sets the state of the selected LED (0 or 1).

The other LED remains untouched.

The following defines are available for this function:

  • DUAL_BUTTON_LED_LEFT = 0
  • DUAL_BUTTON_LED_RIGHT = 1
  • DUAL_BUTTON_LED_STATE_AUTO_TOGGLE_ON = 0
  • DUAL_BUTTON_LED_STATE_AUTO_TOGGLE_OFF = 1
  • DUAL_BUTTON_LED_STATE_ON = 2
  • DUAL_BUTTON_LED_STATE_OFF = 3
int dual_button_get_api_version(DualButton *dual_button, uint8_t ret_api_version[3])

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.

int dual_button_get_response_expected(DualButton *dual_button, uint8_t function_id, bool *ret_response_expected)

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 dual_button_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 send and errors are silently ignored, because they cannot be detected.

See dual_button_set_response_expected() for the list of function ID defines available for this function.

int dual_button_set_response_expected(DualButton *dual_button, uint8_t 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 defines are available for this function:

  • DUAL_BUTTON_FUNCTION_SET_LED_STATE = 1
  • DUAL_BUTTON_FUNCTION_SET_SELECTED_LED_STATE = 5
int dual_button_set_response_expected_all(DualButton *dual_button, bool response_expected)

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

int dual_button_get_identity(DualButton *dual_button, 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)

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.

Callback Configuration Functions

void dual_button_register_callback(DualButton *dual_button, int16_t callback_id, void *function, void *user_data)

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.

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the dual_button_register_callback() function. The parameters consist of the device object, the callback ID, the callback function and optional user data:

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

dual_button_register_callback(&dual_button, DUAL_BUTTON_CALLBACK_EXAMPLE, (void *)my_callback, NULL);

The available constants with corresponding callback 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.

DUAL_BUTTON_CALLBACK_STATE_CHANGED
void callback(uint8_t button_l, uint8_t button_r, uint8_t led_l, uint8_t led_r, void *user_data)

This callback is called whenever a button is pressed.

Possible states for buttons are:

  • 0 = pressed
  • 1 = released

Possible states for LEDs are:

  • 0 = AutoToggleOn: Auto toggle enabled and LED on.
  • 1 = AutoToggleOff: Auto toggle enabled and LED off.
  • 2 = On: LED on (auto toggle is disabled).
  • 3 = Off: LED off (auto toggle is disabled).

The following defines are available for this function:

  • DUAL_BUTTON_BUTTON_STATE_PRESSED = 0
  • DUAL_BUTTON_BUTTON_STATE_RELEASED = 1
  • DUAL_BUTTON_LED_STATE_AUTO_TOGGLE_ON = 0
  • DUAL_BUTTON_LED_STATE_AUTO_TOGGLE_OFF = 1
  • DUAL_BUTTON_LED_STATE_ON = 2
  • DUAL_BUTTON_LED_STATE_OFF = 3

Constants

DUAL_BUTTON_DEVICE_IDENTIFIER

This constant is used to identify a Dual Button Bricklet.

The dual_button_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.

DUAL_BUTTON_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Dual Button Bricklet.