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.
The example code below is Public Domain (CC0 1.0).
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 58 | #include <stdio.h>
#include "ip_connection.h"
#include "bricklet_dual_button.h"
#define HOST "localhost"
#define PORT 4223
#define UID "XYZ" // Change to your UID
// Callback function for illuminance 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; // avoid unused parameter warning
(void)led_r; // avoid unused parameter warning
(void)user_data; // avoid unused parameter warning
if(button_l == DUAL_BUTTON_BUTTON_STATE_PRESSED) {
printf("Left button pressed\n");
} else {
printf("Left button released\n");
}
if(button_r == DUAL_BUTTON_BUTTON_STATE_PRESSED) {
printf("Right button pressed\n");
} else {
printf("Right button released\n");
}
printf("\n");
}
int main() {
// 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");
exit(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();
ipcon_destroy(&ipcon); // Calls ipcon_disconnect internally
}
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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:
as defined in ip_connection.h.
All functions listed below are thread-safe.
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).
Removes the device object dual_button from its IPConnection and destroys it. The device object cannot be used anymore afterwards.
Sets the state of the LEDs. Possible states are:
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:
Returns the current state of the LEDs, as set by dual_button_set_led_state().
The following defines are available for this function:
Returns the current state for both buttons. Possible states are:
The following defines are available for this function:
Sets the state of the selected LED (0 or 1).
The other LED remains untouched.
The following defines are available for this function:
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.
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.
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 defines are available for this function:
Changes the response expected flag for all setter and callback configuration functions of this device at once.
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.
Registers a callback with ID id to the function callback. The user_data will be given as a parameter of the callback.
The available IDs with corresponding function signatures are listed below.
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.
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:
Possible states for LEDs are:
The following defines are available for this function:
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.