C/C++ - Joystick Bricklet

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

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#include <stdio.h>

#include "ip_connection.h"
#include "bricklet_joystick.h"

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

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

    // Create device object
    Joystick j;
    joystick_create(&j, 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 position
    int16_t x, y;
    if(joystick_get_position(&j, &x, &y) < 0) {
        fprintf(stderr, "Could not get position, probably timeout\n");
        return 1;
    }

    printf("Position [X]: %d\n", x);
    printf("Position [Y]: %d\n", y);

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

Callback

Download (example_callback.c)

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#include <stdio.h>

#include "ip_connection.h"
#include "bricklet_joystick.h"

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

// Callback function for pressed callback
void cb_pressed(void *user_data) {
    (void)user_data; // avoid unused parameter warning

    printf("Pressed\n");
}

// Callback function for released callback
void cb_released(void *user_data) {
    (void)user_data; // avoid unused parameter warning

    printf("Released\n");
}

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

    // Create device object
    Joystick j;
    joystick_create(&j, 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 pressed callback to function cb_pressed
    joystick_register_callback(&j,
                               JOYSTICK_CALLBACK_PRESSED,
                               (void *)cb_pressed,
                               NULL);

    // Register released callback to function cb_released
    joystick_register_callback(&j,
                               JOYSTICK_CALLBACK_RELEASED,
                               (void *)cb_released,
                               NULL);

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

Find Borders

Download (example_find_borders.c)

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#include <stdio.h>

#include "ip_connection.h"
#include "bricklet_joystick.h"

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

// Callback function for position reached callback
void cb_position_reached(int16_t x, int16_t y, void *user_data) {
    (void)user_data; // avoid unused parameter warning

    if(y == 100) {
        printf("Top\n");
    } else if(y == -100) {
        printf("Bottom\n");
    }

    if(x == 100) {
        printf("Right\n");
    } else if(x == -100) {
        printf("Left\n");
    }

    printf("\n");
}

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

    // Create device object
    Joystick j;
    joystick_create(&j, 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 0.2 seconds (200ms)
    joystick_set_debounce_period(&j, 200);

    // Register position reached callback to function cb_position_reached
    joystick_register_callback(&j,
                               JOYSTICK_CALLBACK_POSITION_REACHED,
                               (void *)cb_position_reached,
                               NULL);

    // Configure threshold for position "outside of -99, -99 to 99, 99"
    joystick_set_position_callback_threshold(&j, 'o', -99, 99, -99, 99);

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

Windows Mouse

Download (example_windows_mouse.c)

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// This example is Windows only. Link to user32.lib in addition to ws2_32.lib

#include <stdio.h>

#ifdef _WIN32

#include <windows.h>

#include "ip_connection.h"
#include "bricklet_joystick.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XYZ" // Change to your UID

// Fake a mouse button event
void send_mouse_button(uint32_t event) {
    INPUT input;

    memset(&input, 0, sizeof(INPUT));

    input.type = INPUT_MOUSE;
    input.mi.dwFlags = event;

    SendInput(1, &input, sizeof(INPUT));
}

// Fake a mouse move event
void send_mouse_move(int16_t x, int16_t y) {
    INPUT input;
    memset(&input, 0, sizeof(INPUT));

    input.type = INPUT_MOUSE;
    input.mi.dx = x;
    input.mi.dy = y;
    input.mi.dwFlags = MOUSEEVENTF_MOVE;

    SendInput(1, &input, sizeof(INPUT));
}

// Callback function for pressed and released events
void cb_pressed(void *user_data) {
    (void)user_data; // avoid unused parameter warning

    send_mouse_button(MOUSEEVENTF_LEFTDOWN);
}

void cb_released(void *user_data) {
    (void)user_data; // avoid unused parameter warning

    send_mouse_button(MOUSEEVENTF_LEFTUP);
}

// Joystick moves mouse and the button is mapped to left mouse button
int main(void) {
    // Create IP connection
    IPConnection ipcon;
    ipcon_create(&ipcon);

    // Create device object
    Joystick j;
    joystick_create(&j, 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 pressed callback to function cb_pressed
    joystick_register_callback(&j,
                               JOYSTICK_CALLBACK_PRESSED,
                               (void *)cb_pressed,
                               NULL);

    // Register released callback to function cb_released
    joystick_register_callback(&j,
                               JOYSTICK_CALLBACK_RELEASED,
                               (void *)cb_released,
                               NULL);

    printf("Press ctrl+c to exit\n");

    while(true) {
        // Get current position
        int16_t x, y;
        if(joystick_get_position(&j, &x, &y) < 0) {
            fprintf(stderr, "Could not get position, probably timeout\n");
            return 1;
        }

        x = x / 4; // Slow down by factor of 4
        y = -y / 4; // Slow down by factor of 4 and invert axis

        send_mouse_move(x, y);

        Sleep(25); // Check Joystick position every 0.025s (25ms)
    }

    ipcon_destroy(&ipcon); // Calls ipcon_disconnect internally
    return 0;
}

#else

int main(void) {
    printf("This example is Windows only!\n");
    return 0;
}

#endif

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 joystick_create(Joystick *joystick, const char *uid, IPConnection *ipcon)

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

Joystick joystick;
joystick_create(&joystick, "YOUR_DEVICE_UID", &ipcon);

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

void joystick_destroy(Joystick *joystick)

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

int joystick_get_position(Joystick *joystick, int16_t *ret_x, int16_t *ret_y)

Returns the position of the Joystick. The value ranges between -100 and 100 for both axis. The middle position of the joystick is x=0, y=0. The returned values are averaged and calibrated (see joystick_calibrate()).

If you want to get the position periodically, it is recommended to use the JOYSTICK_CALLBACK_POSITION callback and set the period with joystick_set_position_callback_period().

int joystick_is_pressed(Joystick *joystick, bool *ret_pressed)

Returns true if the button is pressed and false otherwise.

It is recommended to use the JOYSTICK_CALLBACK_PRESSED and JOYSTICK_CALLBACK_RELEASED callbacks to handle the button.

Advanced Functions

int joystick_get_analog_value(Joystick *joystick, uint16_t *ret_x, uint16_t *ret_y)

Returns the values as read by a 12-bit analog-to-digital converter. The values are between 0 and 4095 for both axis.

Note

The values returned by joystick_get_position() are averaged over several samples to yield less noise, while joystick_get_analog_value() gives back raw unfiltered analog values. The only reason to use joystick_get_analog_value() is, if you need the full resolution of the analog-to-digital converter.

If you want the analog values periodically, it is recommended to use the JOYSTICK_CALLBACK_ANALOG_VALUE callback and set the period with joystick_set_analog_value_callback_period().

int joystick_calibrate(Joystick *joystick)

Calibrates the middle position of the Joystick. If your Joystick Bricklet does not return x=0 and y=0 in the middle position, call this function while the Joystick is standing still in the middle position.

The resulting calibration will be saved on the EEPROM of the Joystick Bricklet, thus you only have to calibrate it once.

int joystick_get_api_version(Joystick *joystick, 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 joystick_get_response_expected(Joystick *joystick, 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 joystick_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 joystick_set_response_expected() for the list of function ID defines available for this function.

int joystick_set_response_expected(Joystick *joystick, 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:

  • JOYSTICK_FUNCTION_CALIBRATE = 4
  • JOYSTICK_FUNCTION_SET_POSITION_CALLBACK_PERIOD = 5
  • JOYSTICK_FUNCTION_SET_ANALOG_VALUE_CALLBACK_PERIOD = 7
  • JOYSTICK_FUNCTION_SET_POSITION_CALLBACK_THRESHOLD = 9
  • JOYSTICK_FUNCTION_SET_ANALOG_VALUE_CALLBACK_THRESHOLD = 11
  • JOYSTICK_FUNCTION_SET_DEBOUNCE_PERIOD = 13
int joystick_set_response_expected_all(Joystick *joystick, bool response_expected)

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

int joystick_get_identity(Joystick *joystick, 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 joystick_register_callback(Joystick *joystick, 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.

int joystick_set_position_callback_period(Joystick *joystick, uint32_t period)

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

The JOYSTICK_CALLBACK_POSITION callback is only triggered if the position has changed since the last triggering.

The default value is 0.

int joystick_get_position_callback_period(Joystick *joystick, uint32_t *ret_period)

Returns the period as set by joystick_set_position_callback_period().

int joystick_set_analog_value_callback_period(Joystick *joystick, uint32_t period)

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

The JOYSTICK_CALLBACK_ANALOG_VALUE callback is only triggered if the analog values have changed since the last triggering.

The default value is 0.

int joystick_get_analog_value_callback_period(Joystick *joystick, uint32_t *ret_period)

Returns the period as set by joystick_set_analog_value_callback_period().

int joystick_set_position_callback_threshold(Joystick *joystick, char option, int16_t min_x, int16_t max_x, int16_t min_y, int16_t max_y)

Sets the thresholds for the JOYSTICK_CALLBACK_POSITION_REACHED callback.

The following options are possible:

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

The default value is ('x', 0, 0, 0, 0).

The following defines are available for this function:

  • JOYSTICK_THRESHOLD_OPTION_OFF = 'x'
  • JOYSTICK_THRESHOLD_OPTION_OUTSIDE = 'o'
  • JOYSTICK_THRESHOLD_OPTION_INSIDE = 'i'
  • JOYSTICK_THRESHOLD_OPTION_SMALLER = '<'
  • JOYSTICK_THRESHOLD_OPTION_GREATER = '>'
int joystick_get_position_callback_threshold(Joystick *joystick, char *ret_option, int16_t *ret_min_x, int16_t *ret_max_x, int16_t *ret_min_y, int16_t *ret_max_y)

Returns the threshold as set by joystick_set_position_callback_threshold().

The following defines are available for this function:

  • JOYSTICK_THRESHOLD_OPTION_OFF = 'x'
  • JOYSTICK_THRESHOLD_OPTION_OUTSIDE = 'o'
  • JOYSTICK_THRESHOLD_OPTION_INSIDE = 'i'
  • JOYSTICK_THRESHOLD_OPTION_SMALLER = '<'
  • JOYSTICK_THRESHOLD_OPTION_GREATER = '>'
int joystick_set_analog_value_callback_threshold(Joystick *joystick, char option, uint16_t min_x, uint16_t max_x, uint16_t min_y, uint16_t max_y)

Sets the thresholds for the JOYSTICK_CALLBACK_ANALOG_VALUE_REACHED callback.

The following options are possible:

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

The default value is ('x', 0, 0, 0, 0).

The following defines are available for this function:

  • JOYSTICK_THRESHOLD_OPTION_OFF = 'x'
  • JOYSTICK_THRESHOLD_OPTION_OUTSIDE = 'o'
  • JOYSTICK_THRESHOLD_OPTION_INSIDE = 'i'
  • JOYSTICK_THRESHOLD_OPTION_SMALLER = '<'
  • JOYSTICK_THRESHOLD_OPTION_GREATER = '>'
int joystick_get_analog_value_callback_threshold(Joystick *joystick, char *ret_option, uint16_t *ret_min_x, uint16_t *ret_max_x, uint16_t *ret_min_y, uint16_t *ret_max_y)

Returns the threshold as set by joystick_set_analog_value_callback_threshold().

The following defines are available for this function:

  • JOYSTICK_THRESHOLD_OPTION_OFF = 'x'
  • JOYSTICK_THRESHOLD_OPTION_OUTSIDE = 'o'
  • JOYSTICK_THRESHOLD_OPTION_INSIDE = 'i'
  • JOYSTICK_THRESHOLD_OPTION_SMALLER = '<'
  • JOYSTICK_THRESHOLD_OPTION_GREATER = '>'
int joystick_set_debounce_period(Joystick *joystick, uint32_t debounce)

Sets the period in ms with which the threshold callbacks

are triggered, if the thresholds

keep being reached.

The default value is 100.

int joystick_get_debounce_period(Joystick *joystick, uint32_t *ret_debounce)

Returns the debounce period as set by joystick_set_debounce_period().

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the joystick_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);
}

joystick_register_callback(&joystick, JOYSTICK_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.

JOYSTICK_CALLBACK_POSITION
void callback(int16_t x, int16_t y, void *user_data)

This callback is triggered periodically with the period that is set by joystick_set_position_callback_period(). The parameter is the position of the Joystick.

The JOYSTICK_CALLBACK_POSITION callback is only triggered if the position has changed since the last triggering.

JOYSTICK_CALLBACK_ANALOG_VALUE
void callback(uint16_t x, uint16_t y, void *user_data)

This callback is triggered periodically with the period that is set by joystick_set_analog_value_callback_period(). The parameters are the analog values of the Joystick.

The JOYSTICK_CALLBACK_ANALOG_VALUE callback is only triggered if the values have changed since the last triggering.

JOYSTICK_CALLBACK_POSITION_REACHED
void callback(int16_t x, int16_t y, void *user_data)

This callback is triggered when the threshold as set by joystick_set_position_callback_threshold() is reached. The parameters are the position of the Joystick.

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

JOYSTICK_CALLBACK_ANALOG_VALUE_REACHED
void callback(uint16_t x, uint16_t y, void *user_data)

This callback is triggered when the threshold as set by joystick_set_analog_value_callback_threshold() is reached. The parameters are the analog values of the Joystick.

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

JOYSTICK_CALLBACK_PRESSED
void callback(void *user_data)

This callback is triggered when the button is pressed.

JOYSTICK_CALLBACK_RELEASED
void callback(void *user_data)

This callback is triggered when the button is released.

Constants

JOYSTICK_DEVICE_IDENTIFIER

This constant is used to identify a Joystick Bricklet.

The joystick_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.

JOYSTICK_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Joystick Bricklet.