C/C++ - Piezo Speaker Bricklet

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

Beep

Download (example_beep.c)

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#include <stdio.h>

#include "ip_connection.h"
#include "bricklet_piezo_speaker.h"

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

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

    // Create device object
    PiezoSpeaker ps;
    piezo_speaker_create(&ps, 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

    // Make 2 second beep with a frequency of 1kHz
    piezo_speaker_beep(&ps, 2000, 1000);

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

Morse Code

Download (example_morse_code.c)

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#include <stdio.h>

#include "ip_connection.h"
#include "bricklet_piezo_speaker.h"

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

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

    // Create device object
    PiezoSpeaker ps;
    piezo_speaker_create(&ps, 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

    // Morse SOS with a frequency of 2kHz
    piezo_speaker_morse_code(&ps, "... --- ...", 2000);

    printf("Press key to exit\n");
    getchar();
    piezo_speaker_destroy(&ps);
    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 piezo_speaker_create(PiezoSpeaker *piezo_speaker, const char *uid, IPConnection *ipcon)

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

PiezoSpeaker piezo_speaker;
piezo_speaker_create(&piezo_speaker, "YOUR_DEVICE_UID", &ipcon);

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

void piezo_speaker_destroy(PiezoSpeaker *piezo_speaker)

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

int piezo_speaker_beep(PiezoSpeaker *piezo_speaker, uint32_t duration, uint16_t frequency)

Beeps with the given frequency for the duration in ms. For example: If you set a duration of 1000, with a frequency value of 2000 the piezo buzzer will beep for one second with a frequency of approximately 2 kHz.

Changed in version 2.0.2 (Plugin): A duration of 0 stops the current beep if any, the frequency parameter is ignored. A duration of 4294967295 results in an infinite beep.

The frequency parameter can be set between 585 and 7100.

The Piezo Speaker Bricklet can only approximate the frequency, it will play the best possible match by applying the calibration (see piezo_speaker_calibrate()).

The following defines are available for this function:

  • PIEZO_SPEAKER_BEEP_DURATION_OFF = 0
  • PIEZO_SPEAKER_BEEP_DURATION_INFINITE = 4294967295
int piezo_speaker_morse_code(PiezoSpeaker *piezo_speaker, const char morse[60], uint16_t frequency)

Sets morse code that will be played by the piezo buzzer. The morse code is given as a string consisting of "." (dot), "-" (minus) and " " (space) for dits, dahs and pauses. Every other character is ignored. The second parameter is the frequency (see piezo_speaker_beep()).

For example: If you set the string "...---...", the piezo buzzer will beep nine times with the durations "short short short long long long short short short".

The maximum string size is 60.

Advanced Functions

int piezo_speaker_calibrate(PiezoSpeaker *piezo_speaker, bool *ret_calibration)

The Piezo Speaker Bricklet can play 512 different tones. This function plays each tone and measures the exact frequency back. The result is a mapping between setting value and frequency. This mapping is stored in the EEPROM and loaded on startup.

The Bricklet should come calibrated, you only need to call this function (once) every time you reflash the Bricklet plugin.

Returns true after the calibration finishes.

int piezo_speaker_get_api_version(PiezoSpeaker *piezo_speaker, 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 piezo_speaker_get_response_expected(PiezoSpeaker *piezo_speaker, 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 piezo_speaker_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 piezo_speaker_set_response_expected() for the list of function ID defines available for this function.

int piezo_speaker_set_response_expected(PiezoSpeaker *piezo_speaker, 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:

  • PIEZO_SPEAKER_FUNCTION_BEEP = 1
  • PIEZO_SPEAKER_FUNCTION_MORSE_CODE = 2
int piezo_speaker_set_response_expected_all(PiezoSpeaker *piezo_speaker, bool response_expected)

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

int piezo_speaker_get_identity(PiezoSpeaker *piezo_speaker, 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 piezo_speaker_register_callback(PiezoSpeaker *piezo_speaker, 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 piezo_speaker_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);
}

piezo_speaker_register_callback(&piezo_speaker, PIEZO_SPEAKER_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.

PIEZO_SPEAKER_CALLBACK_BEEP_FINISHED
void callback(void *user_data)

This callback is triggered if a beep set by piezo_speaker_beep() is finished

PIEZO_SPEAKER_CALLBACK_MORSE_CODE_FINISHED
void callback(void *user_data)

This callback is triggered if the playback of the morse code set by piezo_speaker_morse_code() is finished.

Constants

PIEZO_SPEAKER_DEVICE_IDENTIFIER

This constant is used to identify a Piezo Speaker Bricklet.

The piezo_speaker_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.

PIEZO_SPEAKER_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Piezo Speaker Bricklet.