HiFi Module Serial Interface

Description

Allows the state machine or PC to load and play sounds using the Bpod HiFi Module.

Requires a Bpod HiFi module with firmware loaded from:

• https://github.com/sanworks/Bpod_HiFi_Firmware

The HiFi module must be connected to a module port on the state machine to use the state machine interface.

State Machine Command Interface

The state machine command interface consists of bytes sent from the Bpod state machine to the HiFi module to start and stop playback, and control synth.

• • Byte 255 (reserved): Returns module info to state machine

  • 'P' (ASCII 80): Plays a sound.

    • 'P' (byte 0) must be followed by one byte:

      • Byte 1: The sound to play (zero-indexed).

  • '*' (ASCII 42): Push any loaded sounds to current playback buffers.

    • Note: This op will make any sounds loaded recently current at the loaded positions, replacing any sounds at those positions.

      • Thus, if new sounds for positions 2 and 3 are loaded during a trial for use on the next trial, sending '*' will make these waveforms the current sounds at positions 2 and 3.

    • If called from the PC via USB, The HiFi module returns a byte (1) to confirm that it has finished pushing loaded sounds.

  • 'X' (ASCII 88): Stop all playback

  • 'x' (ASCII 120): Stop playing a specific sound (if that sound happens to be playing)

    • 'x' (byte 0) must be followed by one byte:

      • Byte 1: The sound to stop (zero-indexed).

  • 'N' (ASCII 78): Set Synth Amplitude. 'N' (byte 0) is followed by:

    • Bytes 1-2: synthAmplitude (16-bit unsigned integer)

    • synthAmplitude must be in range 0-32767 where 0 = no synth, and 32767 = max amplitude (i.e. this is an attenuation factor in bits)

    • If called from the PC via USB, The HiFi module returns a byte (1) to confirm that it has finished setting synth amplitude.

  • 'F' (ASCII 78): Set Synth Frequency. 'F' (byte 0) is followed by:

    • Bytes 1-4: synthFrequency (32-bit unsigned integer)

    • synthFrequency is the target frequency *1000 (e.g. to set 100Hz, use 100000)

    • synthFrequency is ignored if the current waveform is white noise.

    • If called from the PC via USB, The HiFi module returns a byte (1) to confirm that it has finished setting synth frequency.

  • 'W' (ASCII 78): Set Synth Waveform. 'W' (byte 0) is followed by:

    • Byte 1: Waveform type. Values are 0: White Noise, 1: Sine

    • If called from the PC via USB, The HiFi module returns a byte (1) to confirm that it has finished setting synth waveform.

SerialUSB Command Interface

The SerialUSB command interface allows configuration of the HiFi module from MATLAB or Python before a trial begins. The BpodHiFi class for Bpod/MATLAB wraps this interface. The first several commands are the same as for the state machine interface, and additional commands follow.

• • (ASCII 243): Handshake. The module replies with the following sequence of bytes:

    • handshakeReply (1 byte); Equal to 244

  • 'L' (ASCII 76): Load an audio waveform. 'L' (byte 0) is followed by:

    • Byte 1: The waveform to load (0-19). Note: In the HiFiModule class, these are corrected for MATLAB's indexing (1-20).

    • Byte 2: isStereo (set to 1 if loading a stereo/2ch waveform, or 0 if mono/1ch). Note: Both speakers play mono waveforms.

    • Bytes 3 - 6: The number of samples in the audio waveform expressed as a 32-bit integer (1-1,000,000).

    • Bytes 7 - (7+((2 + (2*isStereo))*nSamples)): The waveform. Each byte is a 16-bit signed integer coding for an audio sample.

    • The HiFi module returns a byte (1) to confirm that it has finished reading the last sample.

  • 'S' (ASCII 83): Set sampling rate (units = Hz). 'S' (byte 0) is followed by:

    • Bytes 1-4: Sampling rate in hz (32-bit unsigned integer)

    • Note that only 44100, 48000, 96000 and 192000 are valid sampling rates

    • The HiFi module returns a byte (1) to confirm that it has finished setting the sampling period.

  • 'E' (ASCII 69): Enable AM envelope. 'E' (byte 0) is followed by:

    • Byte 1: UseAMEnvelope: 1 if using AM envelope, 0 if not.

    • The HiFi module returns a byte (1) to confirm that it has finished setting the AM envelope.

  • 'M' (ASCII 77): Load AM envelope. 'M' (byte 0) is followed by:

    • Bytes 1-2: EnvelopeSize (16-bit unsigned int): The number of samples in the envelope

    • Bytes 3-(3+EnvelopeSize*4): samples of the 16-bit AM envelope. These are 4-byte floats (attenuating factors) in range [0 to 1].

    • The HiFi module returns a byte (1) to confirm that it has finished storing the AM envelope.

  • 'O' (ASCII 79): Set loop mode for a waveform. 'O' (byte 0) is followed by:

    • Bytes 1-20: Loop mode bytes. Each byte represents a waveform: 1 if using loop mode, 0 if not.

    • The HiFi module returns a byte (1) to confirm that it has finished setting the loop mode.

  • '-' (ASCII 45): Set duration for looping playback on a single trigger. '-' (byte 0) is followed by:

    • Bytes 1-21: Duration of looped playback on trigger for each waveform (expressed in samples) as a 32-bit integer.

      • Note: Because loop duration is expressed in samples, it must be re-loaded following sampling rate changes (see op above, 'S')

    • The HiFi module returns a byte (1) to confirm that it has finished setting the loop duration.

  • 'A' (ASCII 65): Set digital attenuation. 'A' (byte 0) is followed by:

    • Byte 1: Digital attenuation. Valid values are in range 0-240

    • The HiFi module returns a byte (1) to confirm that it has finished setting the digital attenuation.

  • 'I' (ASCII 78): Return system info. Nothing follows byte 'I'. The module replies with the following sequence of bytes:

    • isHD(1 byte); Corresponds to HiFiBerry DAC board (0 = DAC2 Pro, 1 = DAC2 HD)

    • bitDepth (1 byte); Bit depth of audio samples. Possible values are 16 or 24 (current firmware supports 16 bit only)

    • maxWaves (1 byte); Maximum number of waveforms that can be loaded

    • digitalAttenuation (1 byte); Digital attenuation. dB = digitalAttenuation*-0.5

    • samplingRate (4 bytes; 32-bit int); Current sampling rate in Hz

    • maxSecondsPerWaveform (4 bytes; 32-bit int); Maximum number of seconds that can be stored for a 192kHz stereo waveform

    • maxEnvelopeSize (4 bytes; 32-bit int); Maximum number of samples in the configurable onset/offset AM envelope

Examples

% 1. Play sound# 4 using an ArCOM serial object in MATLAB:

D = ArCOMObject('COM3', 115200);

D.write(['P' 3], 'uint8'); % Remember that sound position is 0-indexed!

clear D

% 2. Trigger sound# 4 from the Bpod state machine

LoadSerialMessages('HiFi1', {['P' 3]}); % Set serial message 1

sma = NewStateMachine();

sma = AddState(sma, 'Name', 'PlaySound', ...

'Timer', 0.1,...

'StateChangeConditions', {'Tup', 'exit'},...

'OutputActions', {'HiFi1', 1}); % Sends serial message 1

SendStateMachine(sma);

RawEvents = RunStateMachine;