Description

The HiFi module is a premium audio solution for Bpod. Its SD and HD versions bring two high resolution Raspberry Pi sound cards under real-time control in the Arduino language using the Teensy 4.1 microcontroller platform. Audio waveforms are transferred to the device via USB, and played back on trigger from the Bpod finite state machine with ~220 microseconds of latency. The HiFi module supports stereo output at sampling rates up to 192kHz. An isolated TTL output channel provides a synchronization signal for external instruments to capture sound onset and offset times. Synthesis functions are provided to render white noise and pure tones with configurable frequency and amplitude. The next trial's waveforms can be loaded to the device without interrupting playback, for usage with TrialManager and BControl. The SD and HD versions of the module hardware differ only in the sound card used: HiFiBerry DAC2 Pro and HiFiBerry DAC2 HD respectively. The HiFi module is intended to replace usage of PC sound cards for nearly all Bpod applications.

Specifications

Compatability

• Bpod FSM must be v0.7 or newer.

Processor

• ARM Cortex M7: NXP i.MX RT1060 Crossover as part of the Teensy 4.1 embedded computing platform
• 600MHz Clock Speed
• 1MB RAM
• Programmable in the Arduino language

Analog Output

• Audio card: HiFiBerry DAC2 HD
• Audio DAC: TI/Burr-Brown PCM1796
• Audio clock source: external precision clock IC
• Stereo output Channels (L, R)
• Zero-centered output
• Voltage range: +/-3V
• Connector type: RCA

Digital Output (Sync)

• Galvanically isolated logic driver
• 3.3V TTL
• BNC connector
• Logic transitions signal sound onset and offset

Serial I/O

• Bpod Module Interface (RS-485 buffered UART, 1.3Mb/s)
• High speed USB 2.0 Interface

Firmware Features

• Sound slots: 20
• Max Sound Duration (per slot): 30s @ 192kHz Stereo
• Configurable sampling rates: 44.1, 48, 96 or 192kHz
• 16-bit sample resolution supported (hardware is 24-bit capable)
• USB sound data transfer at ~40-50Mb/s does not interrupt playback
• 'Push' command adds newly loaded waveforms to the active sound set (e.g. on trial start)
• Digital attenuation control, constrains the audio DAC output signal range
• Customizable AM Envelope applied at sound onset/offset to mitigate speaker pop
• Loop mode (following trigger, loops a waveform for a specified amount of time)
• Synth waveforms: White Noise, Sine
• Synth amplitude and frequency control
• Configurable synth amplitude transition time

Memory

• 16GB MicroSD card included

Dimensions

• L: 10cm (4")
• W: 8cm (3.15")
• H: 6cm (2.3")