C/C++ - Sound Pressure Level Bricklet

This is the description of the C/C++ API bindings for the Sound Pressure Level Bricklet. General information and technical specifications for the Sound Pressure Level 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_sound_pressure_level.h"

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

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

    // Create device object
    SoundPressureLevel spl;
    sound_pressure_level_create(&spl, 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 decibel
    uint16_t decibel;
    if(sound_pressure_level_get_decibel(&spl, &decibel) < 0) {
        fprintf(stderr, "Could not get decibel, probably timeout\n");
        return 1;
    }

    printf("Decibel: %f dB(A)\n", decibel/10.0);

    printf("Press key to exit\n");
    getchar();
    sound_pressure_level_destroy(&spl);
    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_sound_pressure_level.h"

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

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

    printf("Decibel: %f dB(A)\n", decibel/10.0);
}

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

    // Create device object
    SoundPressureLevel spl;
    sound_pressure_level_create(&spl, 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 decibel callback to function cb_decibel
    sound_pressure_level_register_callback(&spl,
                                           SOUND_PRESSURE_LEVEL_CALLBACK_DECIBEL,
                                           (void (*)(void))cb_decibel,
                                           NULL);

    // Set period for decibel callback to 1s (1000ms) without a threshold
    sound_pressure_level_set_decibel_callback_configuration(&spl, 1000, false, 'x', 0, 0);

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

Threshold

Download (example_threshold.c)

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#include <stdio.h>

#include "ip_connection.h"
#include "bricklet_sound_pressure_level.h"

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

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

    printf("Decibel: %f dB(A)\n", decibel/10.0);
}

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

    // Create device object
    SoundPressureLevel spl;
    sound_pressure_level_create(&spl, 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 decibel callback to function cb_decibel
    sound_pressure_level_register_callback(&spl,
                                           SOUND_PRESSURE_LEVEL_CALLBACK_DECIBEL,
                                           (void (*)(void))cb_decibel,
                                           NULL);

    // Configure threshold for decibel "greater than 60 dB(A)"
    // with a debounce period of 1s (1000ms)
    sound_pressure_level_set_decibel_callback_configuration(&spl, 1000, false, '>', 60*10, 0);

    printf("Press key to exit\n");
    getchar();
    sound_pressure_level_destroy(&spl);
    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 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

as defined in ip_connection.h.

All functions listed below are thread-safe.

Basic Functions

void sound_pressure_level_create(SoundPressureLevel *sound_pressure_level, const char *uid, IPConnection *ipcon)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
  • uid – Type: const char *
  • ipcon – Type: IPConnection *

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

SoundPressureLevel sound_pressure_level;
sound_pressure_level_create(&sound_pressure_level, "YOUR_DEVICE_UID", &ipcon);

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

void sound_pressure_level_destroy(SoundPressureLevel *sound_pressure_level)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *

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

int sound_pressure_level_get_decibel(SoundPressureLevel *sound_pressure_level, uint16_t *ret_decibel)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
Output Parameters:
  • ret_decibel – Type: uint16_t, Unit: 1/10 dB, Range: [0 to 120]
Returns:
  • error_code – Type: int

Returns the measured sound pressure in decibels.

The Bricklet supports the weighting standards dB(A), dB(B), dB(C), dB(D), dB(Z) and ITU-R 468. You can configure the weighting with sound_pressure_level_set_configuration().

By default dB(A) will be used.

If you want to get the value periodically, it is recommended to use the SOUND_PRESSURE_LEVEL_CALLBACK_DECIBEL callback. You can set the callback configuration with sound_pressure_level_set_decibel_callback_configuration().

int sound_pressure_level_get_spectrum(SoundPressureLevel *sound_pressure_level, uint16_t *ret_spectrum, uint16_t *ret_spectrum_length)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
Output Parameters:
  • ret_spectrum – Type: uint16_t *, Unit: ? dB, Range: [0 to 216 - 1]
  • ret_spectrum_length – Type: uint16_t
Returns:
  • error_code – Type: int

Returns the frequency spectrum. The length of the spectrum is between 512 (FFT size 1024) and 64 (FFT size 128). See sound_pressure_level_set_configuration().

Each array element is one bin of the FFT. The first bin is always the DC offset and the other bins have a size between 40Hz (FFT size 1024) and 320Hz (FFT size 128).

In sum the frequency of the spectrum always has a range from 0 to 20480Hz (the FFT is applied to samples with a frequency of 40960Hz).

The returned data is already equalized, which means that the microphone frequency response is compensated and the weighting function is applied (see sound_pressure_level_set_configuration() for the available weighting standards). Use dB(Z) if you need the unaltered spectrum.

The values are not in dB form yet. If you want a proper dB scale of the spectrum you have to apply the formula f(x) = 20*log10(max(1, x/sqrt(2))) on each value.

int sound_pressure_level_set_configuration(SoundPressureLevel *sound_pressure_level, uint8_t fft_size, uint8_t weighting)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
  • fft_size – Type: uint8_t, Range: See constants, Default: 3
  • weighting – Type: uint8_t, Range: See constants, Default: 0
Returns:
  • error_code – Type: int

Sets the Sound Pressure Level Bricklet configuration.

With different FFT sizes the Bricklet has a different amount of samples per second and the size of the FFT bins changes. The higher the FFT size the more precise is the result of the dB(X) calculation.

Available FFT sizes are:

  • 1024: 512 bins, 10 samples per second, each bin has size 40Hz
  • 512: 256 bins, 20 samples per second, each bin has size 80Hz
  • 256: 128 bins, 40 samples per second, each bin has size 160Hz
  • 128: 64 bins, 80 samples per second, each bin has size 320Hz

The Bricklet supports different weighting functions. You can choose between dB(A), dB(B), dB(C), dB(D), dB(Z) and ITU-R 468.

dB(A/B/C/D) are the standard dB weighting curves. dB(A) is often used to measure volumes at concerts etc. dB(Z) has a flat response, no weighting is applied. ITU-R 468 is an ITU weighting standard mostly used in the UK and Europe.

The following constants are available for this function:

For fft_size:

  • SOUND_PRESSURE_LEVEL_FFT_SIZE_128 = 0
  • SOUND_PRESSURE_LEVEL_FFT_SIZE_256 = 1
  • SOUND_PRESSURE_LEVEL_FFT_SIZE_512 = 2
  • SOUND_PRESSURE_LEVEL_FFT_SIZE_1024 = 3

For weighting:

  • SOUND_PRESSURE_LEVEL_WEIGHTING_A = 0
  • SOUND_PRESSURE_LEVEL_WEIGHTING_B = 1
  • SOUND_PRESSURE_LEVEL_WEIGHTING_C = 2
  • SOUND_PRESSURE_LEVEL_WEIGHTING_D = 3
  • SOUND_PRESSURE_LEVEL_WEIGHTING_Z = 4
  • SOUND_PRESSURE_LEVEL_WEIGHTING_ITU_R_468 = 5
int sound_pressure_level_get_configuration(SoundPressureLevel *sound_pressure_level, uint8_t *ret_fft_size, uint8_t *ret_weighting)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
Output Parameters:
  • ret_fft_size – Type: uint8_t, Range: See constants, Default: 3
  • ret_weighting – Type: uint8_t, Range: See constants, Default: 0
Returns:
  • error_code – Type: int

Returns the configuration as set by sound_pressure_level_set_configuration().

The following constants are available for this function:

For ret_fft_size:

  • SOUND_PRESSURE_LEVEL_FFT_SIZE_128 = 0
  • SOUND_PRESSURE_LEVEL_FFT_SIZE_256 = 1
  • SOUND_PRESSURE_LEVEL_FFT_SIZE_512 = 2
  • SOUND_PRESSURE_LEVEL_FFT_SIZE_1024 = 3

For ret_weighting:

  • SOUND_PRESSURE_LEVEL_WEIGHTING_A = 0
  • SOUND_PRESSURE_LEVEL_WEIGHTING_B = 1
  • SOUND_PRESSURE_LEVEL_WEIGHTING_C = 2
  • SOUND_PRESSURE_LEVEL_WEIGHTING_D = 3
  • SOUND_PRESSURE_LEVEL_WEIGHTING_Z = 4
  • SOUND_PRESSURE_LEVEL_WEIGHTING_ITU_R_468 = 5

Advanced Functions

int sound_pressure_level_get_spitfp_error_count(SoundPressureLevel *sound_pressure_level, uint32_t *ret_error_count_ack_checksum, uint32_t *ret_error_count_message_checksum, uint32_t *ret_error_count_frame, uint32_t *ret_error_count_overflow)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
Output Parameters:
  • ret_error_count_ack_checksum – Type: uint32_t, Range: [0 to 232 - 1]
  • ret_error_count_message_checksum – Type: uint32_t, Range: [0 to 232 - 1]
  • ret_error_count_frame – Type: uint32_t, Range: [0 to 232 - 1]
  • ret_error_count_overflow – Type: uint32_t, Range: [0 to 232 - 1]
Returns:
  • error_code – Type: int

Returns the error count for the communication between Brick and Bricklet.

The errors are divided into

  • ACK checksum errors,
  • message checksum errors,
  • framing errors and
  • overflow errors.

The errors counts are for errors that occur on the Bricklet side. All Bricks have a similar function that returns the errors on the Brick side.

int sound_pressure_level_set_bootloader_mode(SoundPressureLevel *sound_pressure_level, uint8_t mode, uint8_t *ret_status)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
  • mode – Type: uint8_t, Range: See constants
Output Parameters:
  • ret_status – Type: uint8_t, Range: See constants
Returns:
  • error_code – Type: int

Sets the bootloader mode and returns the status after the requested mode change was instigated.

You can change from bootloader mode to firmware mode and vice versa. A change from bootloader mode to firmware mode will only take place if the entry function, device identifier and CRC are present and correct.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

The following constants are available for this function:

For mode:

  • SOUND_PRESSURE_LEVEL_BOOTLOADER_MODE_BOOTLOADER = 0
  • SOUND_PRESSURE_LEVEL_BOOTLOADER_MODE_FIRMWARE = 1
  • SOUND_PRESSURE_LEVEL_BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
  • SOUND_PRESSURE_LEVEL_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
  • SOUND_PRESSURE_LEVEL_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4

For ret_status:

  • SOUND_PRESSURE_LEVEL_BOOTLOADER_STATUS_OK = 0
  • SOUND_PRESSURE_LEVEL_BOOTLOADER_STATUS_INVALID_MODE = 1
  • SOUND_PRESSURE_LEVEL_BOOTLOADER_STATUS_NO_CHANGE = 2
  • SOUND_PRESSURE_LEVEL_BOOTLOADER_STATUS_ENTRY_FUNCTION_NOT_PRESENT = 3
  • SOUND_PRESSURE_LEVEL_BOOTLOADER_STATUS_DEVICE_IDENTIFIER_INCORRECT = 4
  • SOUND_PRESSURE_LEVEL_BOOTLOADER_STATUS_CRC_MISMATCH = 5
int sound_pressure_level_get_bootloader_mode(SoundPressureLevel *sound_pressure_level, uint8_t *ret_mode)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
Output Parameters:
  • ret_mode – Type: uint8_t, Range: See constants
Returns:
  • error_code – Type: int

Returns the current bootloader mode, see sound_pressure_level_set_bootloader_mode().

The following constants are available for this function:

For ret_mode:

  • SOUND_PRESSURE_LEVEL_BOOTLOADER_MODE_BOOTLOADER = 0
  • SOUND_PRESSURE_LEVEL_BOOTLOADER_MODE_FIRMWARE = 1
  • SOUND_PRESSURE_LEVEL_BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
  • SOUND_PRESSURE_LEVEL_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
  • SOUND_PRESSURE_LEVEL_BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4
int sound_pressure_level_set_write_firmware_pointer(SoundPressureLevel *sound_pressure_level, uint32_t pointer)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
  • pointer – Type: uint32_t, Unit: 1 B, Range: [0 to 232 - 1]
Returns:
  • error_code – Type: int

Sets the firmware pointer for sound_pressure_level_write_firmware(). The pointer has to be increased by chunks of size 64. The data is written to flash every 4 chunks (which equals to one page of size 256).

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

int sound_pressure_level_write_firmware(SoundPressureLevel *sound_pressure_level, uint8_t data[64], uint8_t *ret_status)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
  • data – Type: uint8_t[64], Range: [0 to 255]
Output Parameters:
  • ret_status – Type: uint8_t, Range: [0 to 255]
Returns:
  • error_code – Type: int

Writes 64 Bytes of firmware at the position as written by sound_pressure_level_set_write_firmware_pointer() before. The firmware is written to flash every 4 chunks.

You can only write firmware in bootloader mode.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

int sound_pressure_level_set_status_led_config(SoundPressureLevel *sound_pressure_level, uint8_t config)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
  • config – Type: uint8_t, Range: See constants, Default: 3
Returns:
  • error_code – Type: int

Sets the status LED configuration. By default the LED shows communication traffic between Brick and Bricklet, it flickers once for every 10 received data packets.

You can also turn the LED permanently on/off or show a heartbeat.

If the Bricklet is in bootloader mode, the LED is will show heartbeat by default.

The following constants are available for this function:

For config:

  • SOUND_PRESSURE_LEVEL_STATUS_LED_CONFIG_OFF = 0
  • SOUND_PRESSURE_LEVEL_STATUS_LED_CONFIG_ON = 1
  • SOUND_PRESSURE_LEVEL_STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
  • SOUND_PRESSURE_LEVEL_STATUS_LED_CONFIG_SHOW_STATUS = 3
int sound_pressure_level_get_status_led_config(SoundPressureLevel *sound_pressure_level, uint8_t *ret_config)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
Output Parameters:
  • ret_config – Type: uint8_t, Range: See constants, Default: 3
Returns:
  • error_code – Type: int

Returns the configuration as set by sound_pressure_level_set_status_led_config()

The following constants are available for this function:

For ret_config:

  • SOUND_PRESSURE_LEVEL_STATUS_LED_CONFIG_OFF = 0
  • SOUND_PRESSURE_LEVEL_STATUS_LED_CONFIG_ON = 1
  • SOUND_PRESSURE_LEVEL_STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
  • SOUND_PRESSURE_LEVEL_STATUS_LED_CONFIG_SHOW_STATUS = 3
int sound_pressure_level_get_chip_temperature(SoundPressureLevel *sound_pressure_level, int16_t *ret_temperature)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
Output Parameters:
  • ret_temperature – Type: int16_t, Unit: 1 °C, Range: [-215 to 215 - 1]
Returns:
  • error_code – Type: int

Returns the temperature as measured inside the microcontroller. The value returned is not the ambient temperature!

The temperature is only proportional to the real temperature and it has bad accuracy. Practically it is only useful as an indicator for temperature changes.

int sound_pressure_level_reset(SoundPressureLevel *sound_pressure_level)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
Returns:
  • error_code – Type: int

Calling this function will reset the Bricklet. All configurations will be lost.

After a reset you have to create new device objects, calling functions on the existing ones will result in undefined behavior!

int sound_pressure_level_write_uid(SoundPressureLevel *sound_pressure_level, uint32_t uid)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
  • uid – Type: uint32_t, Range: [0 to 232 - 1]
Returns:
  • error_code – Type: int

Writes a new UID into flash. If you want to set a new UID you have to decode the Base58 encoded UID string into an integer first.

We recommend that you use Brick Viewer to change the UID.

int sound_pressure_level_read_uid(SoundPressureLevel *sound_pressure_level, uint32_t *ret_uid)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
Output Parameters:
  • ret_uid – Type: uint32_t, Range: [0 to 232 - 1]
Returns:
  • error_code – Type: int

Returns the current UID as an integer. Encode as Base58 to get the usual string version.

int sound_pressure_level_get_identity(SoundPressureLevel *sound_pressure_level, 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:
  • sound_pressure_level – Type: SoundPressureLevel *
Output Parameters:
  • ret_uid – Type: char[8]
  • ret_connected_uid – Type: char[8]
  • ret_position – Type: char, Range: ['a' to 'h', 'i', '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:
  • error_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). The Raspberry Pi HAT (Zero) Brick is always at position 'i' and the Bricklet connected to an Isolator Bricklet is always as 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 sound_pressure_level_register_callback(SoundPressureLevel *sound_pressure_level, int16_t callback_id, void (*function)(void), void *user_data)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
  • 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 sound_pressure_level_set_decibel_callback_configuration(SoundPressureLevel *sound_pressure_level, uint32_t period, bool value_has_to_change, char option, uint16_t min, uint16_t max)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
  • period – Type: uint32_t, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0
  • value_has_to_change – Type: bool, Default: false
  • option – Type: char, Range: See constants, Default: 'x'
  • min – Type: uint16_t, Unit: 1/10 dB, Range: [0 to 216 - 1], Default: 0
  • max – Type: uint16_t, Unit: 1/10 dB, Range: [0 to 216 - 1], Default: 0
Returns:
  • error_code – Type: int

The period is the period with which the SOUND_PRESSURE_LEVEL_CALLBACK_DECIBEL callback is triggered periodically. A value of 0 turns the callback off.

If the value has to change-parameter is set to true, the callback is only triggered after the value has changed. If the value didn't change within the period, the callback is triggered immediately on change.

If it is set to false, the callback is continuously triggered with the period, independent of the value.

It is furthermore possible to constrain the callback with thresholds.

The option-parameter together with min/max sets a threshold for the SOUND_PRESSURE_LEVEL_CALLBACK_DECIBEL callback.

The following options are possible:

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

If the option is set to 'x' (threshold turned off) the callback is triggered with the fixed period.

The following constants are available for this function:

For option:

  • SOUND_PRESSURE_LEVEL_THRESHOLD_OPTION_OFF = 'x'
  • SOUND_PRESSURE_LEVEL_THRESHOLD_OPTION_OUTSIDE = 'o'
  • SOUND_PRESSURE_LEVEL_THRESHOLD_OPTION_INSIDE = 'i'
  • SOUND_PRESSURE_LEVEL_THRESHOLD_OPTION_SMALLER = '<'
  • SOUND_PRESSURE_LEVEL_THRESHOLD_OPTION_GREATER = '>'
int sound_pressure_level_get_decibel_callback_configuration(SoundPressureLevel *sound_pressure_level, uint32_t *ret_period, bool *ret_value_has_to_change, char *ret_option, uint16_t *ret_min, uint16_t *ret_max)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
Output Parameters:
  • ret_period – Type: uint32_t, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0
  • ret_value_has_to_change – Type: bool, Default: false
  • ret_option – Type: char, Range: See constants, Default: 'x'
  • ret_min – Type: uint16_t, Unit: 1/10 dB, Range: [0 to 216 - 1], Default: 0
  • ret_max – Type: uint16_t, Unit: 1/10 dB, Range: [0 to 216 - 1], Default: 0
Returns:
  • error_code – Type: int

Returns the callback configuration as set by sound_pressure_level_set_decibel_callback_configuration().

The following constants are available for this function:

For ret_option:

  • SOUND_PRESSURE_LEVEL_THRESHOLD_OPTION_OFF = 'x'
  • SOUND_PRESSURE_LEVEL_THRESHOLD_OPTION_OUTSIDE = 'o'
  • SOUND_PRESSURE_LEVEL_THRESHOLD_OPTION_INSIDE = 'i'
  • SOUND_PRESSURE_LEVEL_THRESHOLD_OPTION_SMALLER = '<'
  • SOUND_PRESSURE_LEVEL_THRESHOLD_OPTION_GREATER = '>'
int sound_pressure_level_set_spectrum_callback_configuration(SoundPressureLevel *sound_pressure_level, uint32_t period)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
  • period – Type: uint32_t, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0
Returns:
  • error_code – Type: int

The period is the period with which the SOUND_PRESSURE_LEVEL_CALLBACK_SPECTRUM callback is triggered periodically. A value of 0 turns the callback off.

Every new measured spectrum will be send at most once. Set the period to 1 to make sure that you get every spectrum.

int sound_pressure_level_get_spectrum_callback_configuration(SoundPressureLevel *sound_pressure_level, uint32_t *ret_period)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
Output Parameters:
  • ret_period – Type: uint32_t, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0
Returns:
  • error_code – Type: int

Returns the callback configuration as set by sound_pressure_level_get_spectrum_callback_configuration().

Callbacks

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

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

sound_pressure_level_register_callback(&sound_pressure_level,
                                       SOUND_PRESSURE_LEVEL_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.

SOUND_PRESSURE_LEVEL_CALLBACK_DECIBEL
void callback(uint16_t decibel, void *user_data)
Callback Parameters:
  • decibel – Type: uint16_t, Unit: 1/10 dB, Range: [0 to 120]
  • user_data – Type: void *

This callback is triggered periodically according to the configuration set by sound_pressure_level_set_decibel_callback_configuration().

The parameter is the same as sound_pressure_level_get_decibel().

SOUND_PRESSURE_LEVEL_CALLBACK_SPECTRUM
void callback(uint16_t *spectrum, uint16_t spectrum_length, void *user_data)
Callback Parameters:
  • spectrum – Type: uint16_t *, Unit: ? dB, Range: [0 to 216 - 1]
  • spectrum_length – Type: uint16_t
  • user_data – Type: void *

This callback is triggered periodically according to the configuration set by sound_pressure_level_set_spectrum_callback_configuration().

The parameter is the same as sound_pressure_level_get_spectrum().

Note

If reconstructing the value fails, the callback is triggered with NULL for spectrum.

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 sound_pressure_level_get_api_version(SoundPressureLevel *sound_pressure_level, uint8_t ret_api_version[3])
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
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:
  • error_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 sound_pressure_level_get_response_expected(SoundPressureLevel *sound_pressure_level, uint8_t function_id, bool *ret_response_expected)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
  • function_id – Type: uint8_t, Range: See constants
Output Parameters:
  • ret_response_expected – Type: bool
Returns:
  • error_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 sound_pressure_level_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.

The following constants are available for this function:

For function_id:

  • SOUND_PRESSURE_LEVEL_FUNCTION_SET_DECIBEL_CALLBACK_CONFIGURATION = 2
  • SOUND_PRESSURE_LEVEL_FUNCTION_SET_SPECTRUM_CALLBACK_CONFIGURATION = 6
  • SOUND_PRESSURE_LEVEL_FUNCTION_SET_CONFIGURATION = 9
  • SOUND_PRESSURE_LEVEL_FUNCTION_SET_WRITE_FIRMWARE_POINTER = 237
  • SOUND_PRESSURE_LEVEL_FUNCTION_SET_STATUS_LED_CONFIG = 239
  • SOUND_PRESSURE_LEVEL_FUNCTION_RESET = 243
  • SOUND_PRESSURE_LEVEL_FUNCTION_WRITE_UID = 248
int sound_pressure_level_set_response_expected(SoundPressureLevel *sound_pressure_level, uint8_t function_id, bool response_expected)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
  • function_id – Type: uint8_t, Range: See constants
  • response_expected – Type: bool
Returns:
  • error_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.

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 constants are available for this function:

For function_id:

  • SOUND_PRESSURE_LEVEL_FUNCTION_SET_DECIBEL_CALLBACK_CONFIGURATION = 2
  • SOUND_PRESSURE_LEVEL_FUNCTION_SET_SPECTRUM_CALLBACK_CONFIGURATION = 6
  • SOUND_PRESSURE_LEVEL_FUNCTION_SET_CONFIGURATION = 9
  • SOUND_PRESSURE_LEVEL_FUNCTION_SET_WRITE_FIRMWARE_POINTER = 237
  • SOUND_PRESSURE_LEVEL_FUNCTION_SET_STATUS_LED_CONFIG = 239
  • SOUND_PRESSURE_LEVEL_FUNCTION_RESET = 243
  • SOUND_PRESSURE_LEVEL_FUNCTION_WRITE_UID = 248
int sound_pressure_level_set_response_expected_all(SoundPressureLevel *sound_pressure_level, bool response_expected)
Parameters:
  • sound_pressure_level – Type: SoundPressureLevel *
  • response_expected – Type: bool
Returns:
  • error_code – Type: int

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

Constants

SOUND_PRESSURE_LEVEL_DEVICE_IDENTIFIER

This constant is used to identify a Sound Pressure Level Bricklet.

The sound_pressure_level_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.

SOUND_PRESSURE_LEVEL_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Sound Pressure Level Bricklet.