Specifications / Modbus Protocol / API / Bricklets / Sound Pressure Level Bricklet

Modbus - Sound Pressure Level Bricklet¶

This is the description of the Modbus protocol for the Sound Pressure Level Bricklet. General information and technical specifications for the Sound Pressure Level Bricklet are summarized in its hardware description.

API¶

A general description of the Modbus protocol structure can be found here.

Basic Functions¶

BrickletSoundPressureLevel.get_decibel¶

Function ID:	1
Request:	empty payload
Response:	decibel – Type: uint16, Unit: 1/10 dB, Range: [0 to 120]

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 set_configuration.

By default dB(A) will be used.

If you want to get the value periodically, it is recommended to use the CALLBACK_DECIBEL callback. You can set the callback configuration with set_decibel_callback_configuration.

BrickletSoundPressureLevel.get_spectrum_low_level¶

Function ID:	5
Request:	empty payload
Response:	spectrum_length – Type: uint16, Range: [64 to 2⁹] spectrum_chunk_offset – Type: uint16, Range: [0 to 2¹⁶ - 1] spectrum_chunk_data – Type: uint16[30], Unit: ? dB, Range: [0 to 2¹⁶ - 1]

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

BrickletSoundPressureLevel.set_configuration¶

Function ID:	9
Request:	fft_size – Type: uint8, Range: See meanings, Default: 3 weighting – Type: uint8, Range: See meanings, Default: 0
Response:	no response

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 meanings are defined for the elements of this function:

For fft_size:

0 = 128
1 = 256
2 = 512
3 = 1024

For weighting:

0 = A
1 = B
2 = C
3 = D
4 = Z
5 = ITU R 468

BrickletSoundPressureLevel.get_configuration¶

Function ID:	10
Request:	empty payload
Response:	fft_size – Type: uint8, Range: See meanings, Default: 3 weighting – Type: uint8, Range: See meanings, Default: 0

Returns the configuration as set by set_configuration.

The following meanings are defined for the elements of this function:

For fft_size:

0 = 128
1 = 256
2 = 512
3 = 1024

For weighting:

0 = A
1 = B
2 = C
3 = D
4 = Z
5 = ITU R 468

Advanced Functions¶

BrickletSoundPressureLevel.get_spitfp_error_count¶

Function ID:	234
Request:	empty payload
Response:	error_count_ack_checksum – Type: uint32, Range: [0 to 2³² - 1] error_count_message_checksum – Type: uint32, Range: [0 to 2³² - 1] error_count_frame – Type: uint32, Range: [0 to 2³² - 1] error_count_overflow – Type: uint32, Range: [0 to 2³² - 1]

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.

BrickletSoundPressureLevel.set_status_led_config¶

Function ID:	239
Request:	config – Type: uint8, Range: See meanings, Default: 3
Response:	no response

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 meanings are defined for the elements of this function:

For config:

0 = Off
1 = On
2 = Show Heartbeat
3 = Show Status

BrickletSoundPressureLevel.get_status_led_config¶

Function ID:	240
Request:	empty payload
Response:	config – Type: uint8, Range: See meanings, Default: 3

Returns the configuration as set by set_status_led_config

The following meanings are defined for the elements of this function:

For config:

0 = Off
1 = On
2 = Show Heartbeat
3 = Show Status

BrickletSoundPressureLevel.get_chip_temperature¶

Function ID:	242
Request:	empty payload
Response:	temperature – Type: int16, Unit: 1 °C, Range: [-2¹⁵ to 2¹⁵ - 1]

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.

BrickletSoundPressureLevel.reset¶

Function ID:	243
Request:	empty payload
Response:	no response

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!

BrickletSoundPressureLevel.get_identity¶

Function ID:	255
Request:	empty payload
Response:	uid – Type: char[8] connected_uid – Type: char[8] position – Type: char, Range: ['a' to 'h', 'z'] hardware_version – Type: uint8[3] 0: major – Type: uint8, Range: [0 to 255] 1: minor – Type: uint8, Range: [0 to 255] 2: revision – Type: uint8, Range: [0 to 255] firmware_version – Type: uint8[3] 0: major – Type: uint8, Range: [0 to 255] 1: minor – Type: uint8, Range: [0 to 255] 2: revision – Type: uint8, Range: [0 to 255] device_identifier – Type: uint16, Range: [0 to 2¹⁶ - 1]

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). A Bricklet connected to an Isolator Bricklet is always at position 'z'.

The device identifier numbers can be found here.

Callback Configuration Functions¶

BrickletSoundPressureLevel.set_decibel_callback_configuration¶

Function ID:	2
Request:	period – Type: uint32, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0 value_has_to_change – Type: bool, Default: false option – Type: char, Range: See meanings, Default: 'x' min – Type: uint16, Unit: 1/10 dB, Range: [0 to 2¹⁶ - 1], Default: 0 max – Type: uint16, Unit: 1/10 dB, Range: [0 to 2¹⁶ - 1], Default: 0
Response:	no response

The period is the period with which the 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 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 meanings are defined for the elements of this function:

For option:

'x' = Off
'o' = Outside
'i' = Inside
'<' = Smaller
'>' = Greater

BrickletSoundPressureLevel.get_decibel_callback_configuration¶

Function ID:	3
Request:	empty payload
Response:	period – Type: uint32, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0 value_has_to_change – Type: bool, Default: false option – Type: char, Range: See meanings, Default: 'x' min – Type: uint16, Unit: 1/10 dB, Range: [0 to 2¹⁶ - 1], Default: 0 max – Type: uint16, Unit: 1/10 dB, Range: [0 to 2¹⁶ - 1], Default: 0

Returns the callback configuration as set by set_decibel_callback_configuration.

The following meanings are defined for the elements of this function:

For option:

'x' = Off
'o' = Outside
'i' = Inside
'<' = Smaller
'>' = Greater

BrickletSoundPressureLevel.set_spectrum_callback_configuration¶

Function ID:	6
Request:	period – Type: uint32, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Response:	no response

The period is the period with which the CALLBACK_SPECTRUM_LOW_LEVEL 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.

BrickletSoundPressureLevel.get_spectrum_callback_configuration¶

Function ID:	7
Request:	empty payload
Response:	period – Type: uint32, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0

Returns the callback configuration as set by get_spectrum_callback_configuration.

Callbacks¶

BrickletSoundPressureLevel.CALLBACK_DECIBEL¶

Function ID:	4
Response:	decibel – Type: uint16, Unit: 1/10 dB, Range: [0 to 120]

This callback is triggered periodically according to the configuration set by set_decibel_callback_configuration.

The response value is the same as get_decibel.

BrickletSoundPressureLevel.CALLBACK_SPECTRUM_LOW_LEVEL¶

Function ID:	8
Response:	spectrum_length – Type: uint16, Range: [64 to 2⁹] spectrum_chunk_offset – Type: uint16, Range: [0 to 2¹⁶ - 1] spectrum_chunk_data – Type: uint16[30], Unit: ? dB, Range: [0 to 2¹⁶ - 1]

This callback is triggered periodically according to the configuration set by set_spectrum_callback_configuration.

The response value is the same as get_spectrum_low_level.

Internal Functions¶

Internal functions are used for maintenance tasks such as flashing a new firmware of changing the UID of a Bricklet. These task should be performed using Brick Viewer instead of using the internal functions directly.

BrickletSoundPressureLevel.set_bootloader_mode¶

Function ID:	235
Request:	mode – Type: uint8, Range: See meanings
Response:	status – Type: uint8, Range: See meanings

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 meanings are defined for the elements of this function:

For mode:

0 = Bootloader
1 = Firmware
2 = Bootloader Wait For Reboot
3 = Firmware Wait For Reboot
4 = Firmware Wait For Erase And Reboot

For status:

0 = OK
1 = Invalid Mode
2 = No Change
3 = Entry Function Not Present
4 = Device Identifier Incorrect
5 = CRC Mismatch

BrickletSoundPressureLevel.get_bootloader_mode¶

Function ID:	236
Request:	empty payload
Response:	mode – Type: uint8, Range: See meanings

Returns the current bootloader mode, see set_bootloader_mode.

The following meanings are defined for the elements of this function:

For mode:

0 = Bootloader
1 = Firmware
2 = Bootloader Wait For Reboot
3 = Firmware Wait For Reboot
4 = Firmware Wait For Erase And Reboot

BrickletSoundPressureLevel.set_write_firmware_pointer¶

Function ID:	237
Request:	pointer – Type: uint32, Unit: 1 B, Range: [0 to 2³² - 1]
Response:	no response

Sets the firmware pointer for 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.

BrickletSoundPressureLevel.write_firmware¶

Function ID:	238
Request:	data – Type: uint8[64], Range: [0 to 255]
Response:	status – Type: uint8, Range: [0 to 255]

Writes 64 Bytes of firmware at the position as written by 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.

BrickletSoundPressureLevel.write_uid¶

Function ID:	248
Request:	uid – Type: uint32, Range: [0 to 2³² - 1]
Response:	no response

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.

BrickletSoundPressureLevel.read_uid¶

Function ID:	249
Request:	empty payload
Response:	uid – Type: uint32, Range: [0 to 2³² - 1]

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