Shell - Sound Pressure Level Bricklet

This is the description of the Shell 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 Shell API bindings is part of their general description.

Examples

The example code below is Public Domain (CC0 1.0).

Simple

Download (example-simple.sh)

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#!/bin/sh
# Connects to localhost:4223 by default, use --host and --port to change this

uid=XYZ # Change XYZ to the UID of your Sound Pressure Level Bricklet

# Get current decibel
tinkerforge call sound-pressure-level-bricklet $uid get-decibel

Callback

Download (example-callback.sh)

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#!/bin/sh
# Connects to localhost:4223 by default, use --host and --port to change this

uid=XYZ # Change XYZ to the UID of your Sound Pressure Level Bricklet

# Handle incoming decibel callbacks
tinkerforge dispatch sound-pressure-level-bricklet $uid decibel &

# Set period for decibel callback to 1s (1000ms) without a threshold
tinkerforge call sound-pressure-level-bricklet $uid set-decibel-callback-configuration 1000 false threshold-option-off 0 0

echo "Press key to exit"; read dummy

kill -- -$$ # Stop callback dispatch in background

Threshold

Download (example-threshold.sh)

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#!/bin/sh
# Connects to localhost:4223 by default, use --host and --port to change this

uid=XYZ # Change XYZ to the UID of your Sound Pressure Level Bricklet

# Handle incoming decibel callbacks
tinkerforge dispatch sound-pressure-level-bricklet $uid decibel &

# Configure threshold for decibel "greater than 60 dB(A)"
# with a debounce period of 1s (1000ms)
tinkerforge call sound-pressure-level-bricklet $uid set-decibel-callback-configuration 1000 false threshold-option-greater 600 0

echo "Press key to exit"; read dummy

kill -- -$$ # Stop callback dispatch in background

API

Possible exit codes for all tinkerforge commands are:

  • 1: interrupted (ctrl+c)
  • 2: syntax error
  • 21: Python 2.5 or newer is required
  • 22: Python argparse module is missing
  • 23: socket error
  • 24: other exception
  • 25: invalid placeholder in format string
  • 26: authentication error
  • 201: timeout occurred
  • 209: invalid argument value
  • 210: function is not supported
  • 211: unknown error

Command Structure

The common options of the call and dispatch commands are documented here. The specific command structure is shown below.

tinkerforge call sound-pressure-level-bricklet [<option>..] <uid> <function> [<argument>..]
Parameters:
  • <uid> -- string
  • <function> -- string

The call command is used to call a function of the Sound Pressure Level Bricklet. It can take several options:

  • --help shows help for the specific call command and exits
  • --list-functions shows a list of known functions of the Sound Pressure Level Bricklet and exits
tinkerforge dispatch sound-pressure-level-bricklet [<option>..] <uid> <callback>
Parameters:
  • <uid> -- string
  • <callback> -- string

The dispatch command is used to dispatch a callback of the Sound Pressure Level Bricklet. It can take several options:

  • --help shows help for the specific dispatch command and exits
  • --list-callbacks shows a list of known callbacks of the Sound Pressure Level Bricklet and exits
tinkerforge call sound-pressure-level-bricklet <uid> <function> [<option>..] [<argument>..]
Parameters:
  • <uid> -- string
  • <function> -- string

The <function> to be called can take different options depending of its kind. All functions can take the following options:

  • --help shows help for the specific function and exits

Getter functions can take the following options:

  • --execute <command> shell command line to execute for each incoming response (see section about output formatting for details)

Setter functions can take the following options:

  • --expect-response requests response and waits for it

The --expect-response option for setter functions allows to detect timeouts and other error conditions calls of setters as well. The device will then send a response for this purpose. If this option is not given for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

tinkerforge dispatch sound-pressure-level-bricklet <uid> <callback> [<option>..]
Parameters:
  • <uid> -- string
  • <callback> -- string

The <callback> to be dispatched can take several options:

  • --help shows help for the specific callback and exits
  • --execute <command> shell command line to execute for each incoming response (see section about output formatting for details)

Basic Functions

tinkerforge call sound-pressure-level-bricklet <uid> get-decibel
Output:
  • decibel -- int

Returns the measured sound pressure in decibels. The values are given in dB/10 (tenths dB).

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 decibel callback. You can set the callback configuration with set-decibel-callback-configuration.

tinkerforge call sound-pressure-level-bricklet <uid> get-spectrum-low-level
Output:
  • spectrum-length -- int
  • spectrum-chunk-offset -- int
  • spectrum-chunk-data -- int,int,..27x..,int

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.

tinkerforge call sound-pressure-level-bricklet <uid> set-configuration <fft-size> <weighting>
Parameters:
  • <fft-size> -- int (has symbols)
  • <weighting> -- int (has symbols)
Output:

no output

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 defaults are FFT size 1024 and weighting standard dB(A).

The following symbols are available for this function:

  • fft-size-128 = 0, for <fft-size>
  • fft-size-256 = 1, for <fft-size>
  • fft-size-512 = 2, for <fft-size>
  • fft-size-1024 = 3, for <fft-size>
  • weighting-a = 0, for <weighting>
  • weighting-b = 1, for <weighting>
  • weighting-c = 2, for <weighting>
  • weighting-d = 3, for <weighting>
  • weighting-z = 4, for <weighting>
  • weighting-itu-r-468 = 5, for <weighting>
tinkerforge call sound-pressure-level-bricklet <uid> get-configuration
Output:
  • fft-size -- int (has symbols)
  • weighting -- int (has symbols)

Returns the configuration as set by set-configuration.

The following symbols are available for this function:

  • fft-size-128 = 0, for fft-size
  • fft-size-256 = 1, for fft-size
  • fft-size-512 = 2, for fft-size
  • fft-size-1024 = 3, for fft-size
  • weighting-a = 0, for weighting
  • weighting-b = 1, for weighting
  • weighting-c = 2, for weighting
  • weighting-d = 3, for weighting
  • weighting-z = 4, for weighting
  • weighting-itu-r-468 = 5, for weighting

Advanced Functions

tinkerforge call sound-pressure-level-bricklet <uid> get-spitfp-error-count
Output:
  • error-count-ack-checksum -- int
  • error-count-message-checksum -- int
  • error-count-frame -- int
  • error-count-overflow -- 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.

tinkerforge call sound-pressure-level-bricklet <uid> set-bootloader-mode <mode>
Parameters:
  • <mode> -- int (has symbols)
Output:
  • status -- int (has symbols)

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 symbols are available for this function:

  • bootloader-mode-bootloader = 0, for <mode>
  • bootloader-mode-firmware = 1, for <mode>
  • bootloader-mode-bootloader-wait-for-reboot = 2, for <mode>
  • bootloader-mode-firmware-wait-for-reboot = 3, for <mode>
  • bootloader-mode-firmware-wait-for-erase-and-reboot = 4, for <mode>
  • bootloader-status-ok = 0, for status
  • bootloader-status-invalid-mode = 1, for status
  • bootloader-status-no-change = 2, for status
  • bootloader-status-entry-function-not-present = 3, for status
  • bootloader-status-device-identifier-incorrect = 4, for status
  • bootloader-status-crc-mismatch = 5, for status
tinkerforge call sound-pressure-level-bricklet <uid> get-bootloader-mode
Output:
  • mode -- int (has symbols)

Returns the current bootloader mode, see set-bootloader-mode.

The following symbols are available for this function:

  • bootloader-mode-bootloader = 0, for mode
  • bootloader-mode-firmware = 1, for mode
  • bootloader-mode-bootloader-wait-for-reboot = 2, for mode
  • bootloader-mode-firmware-wait-for-reboot = 3, for mode
  • bootloader-mode-firmware-wait-for-erase-and-reboot = 4, for mode
tinkerforge call sound-pressure-level-bricklet <uid> set-write-firmware-pointer <pointer>
Parameters:
  • <pointer> -- int
Output:

no output

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.

tinkerforge call sound-pressure-level-bricklet <uid> write-firmware <data>
Parameters:
  • <data> -- int,int,..61x..,int
Output:
  • status -- int

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.

tinkerforge call sound-pressure-level-bricklet <uid> set-status-led-config <config>
Parameters:
  • <config> -- int (has symbols)
Output:

no output

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 symbols are available for this function:

  • status-led-config-off = 0, for <config>
  • status-led-config-on = 1, for <config>
  • status-led-config-show-heartbeat = 2, for <config>
  • status-led-config-show-status = 3, for <config>
tinkerforge call sound-pressure-level-bricklet <uid> get-status-led-config
Output:
  • config -- int (has symbols)

Returns the configuration as set by set-status-led-config

The following symbols are available for this function:

  • status-led-config-off = 0, for config
  • status-led-config-on = 1, for config
  • status-led-config-show-heartbeat = 2, for config
  • status-led-config-show-status = 3, for config
tinkerforge call sound-pressure-level-bricklet <uid> get-chip-temperature
Output:
  • temperature -- int

Returns the temperature in °C 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.

tinkerforge call sound-pressure-level-bricklet <uid> reset
Output:no output

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!

tinkerforge call sound-pressure-level-bricklet <uid> write-uid <uid>
Parameters:
  • <uid> -- int
Output:

no output

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.

tinkerforge call sound-pressure-level-bricklet <uid> read-uid
Output:
  • uid -- int

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

tinkerforge call sound-pressure-level-bricklet <uid> get-identity
Output:
  • uid -- string
  • connected-uid -- string
  • position -- char
  • hardware-version -- int,int,int
  • firmware-version -- int,int,int
  • device-identifier -- int (has symbols)

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

Callback Configuration Functions

tinkerforge call sound-pressure-level-bricklet <uid> set-decibel-callback-configuration <period> <value-has-to-change> <option> <min> <max>
Parameters:
  • <period> -- int
  • <value-has-to-change> -- bool
  • <option> -- char (has symbols)
  • <min> -- int
  • <max> -- int
Output:

no output

The period in ms is the period with which the 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 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 default value is (0, false, 'x', 0, 0).

The following symbols are available for this function:

  • threshold-option-off = x, for <option>
  • threshold-option-outside = o, for <option>
  • threshold-option-inside = i, for <option>
  • threshold-option-smaller = <, for <option>
  • threshold-option-greater = >, for <option>
tinkerforge call sound-pressure-level-bricklet <uid> get-decibel-callback-configuration
Output:
  • period -- int
  • value-has-to-change -- bool
  • option -- char (has symbols)
  • min -- int
  • max -- int

Returns the callback configuration as set by set-decibel-callback-configuration.

The following symbols are available for this function:

  • threshold-option-off = x, for option
  • threshold-option-outside = o, for option
  • threshold-option-inside = i, for option
  • threshold-option-smaller = <, for option
  • threshold-option-greater = >, for option
tinkerforge call sound-pressure-level-bricklet <uid> set-spectrum-callback-configuration <period>
Parameters:
  • <period> -- int
Output:

no output

The period in ms is the period with which the 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.

The default value is 0.

tinkerforge call sound-pressure-level-bricklet <uid> get-spectrum-callback-configuration
Output:
  • period -- int

Returns the callback configuration as set by get-spectrum-callback-configuration.

Callbacks

Callbacks can be used to receive time critical or recurring data from the device:

tinkerforge dispatch sound-pressure-level-bricklet <uid> example

The available callbacks 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.

tinkerforge dispatch sound-pressure-level-bricklet <uid> decibel
Output:
  • decibel -- int

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

The parameter is the same as get-decibel.

tinkerforge dispatch sound-pressure-level-bricklet <uid> spectrum-low-level
Output:
  • spectrum-length -- int
  • spectrum-chunk-offset -- int
  • spectrum-chunk-data -- int,int,..27x..,int

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

The parameter is the same as get-spectrum.