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Sonochan MkII (SMkII in further text) is an USB Audio device designed with I2S/Digital audio measurement and testing in mind.
It is fork of the SDR-Widget project, but further designed as self-contained fully-configurable and somewhat robust measurement tool.
The basic idea of SMkII is to provide two functions:
-
Output digital audio stream on it's I2S port output without loosing samples or altering/resampling the original audio source. For that reason, it can use the adaptive clock generation, changing it's CLK speed based on the status of the buffer.
-
Record digital audio stream from it's I2S port input without altering/resampling the samples
Usual audio recording/playback tools such as Audacity can be used to play/record audio on SMkII. Obviously, to fulfill (1.), SMkII in adaptive CLK mode may deliberately introduce jitter, therefore it's not suitable for analog-domain measurements.
To a PC-Based OS, SMkII looks like a standard USB Audio device. To a device under test (DUT), SMkII looks like an I2S signal source or sink.
- USB Audio Class 1
- Stereo, full duplex
- Supported sampling rates&bit-depths: 8, 11.2, 16, 24, 32, 44.1, 48 kHz @ 16 bit
- Supported digital audio formats: I2S/PCM/TDM/LJS/RJS with variable bit-shift and L/R channel setting
- Fixed-settable or adaptive MCLK setting
- Headphone output (with TX/RX source stream selector) for listening confirmation of ongoing measurement
- Galvanically isolated I2S port to prevent damage, ground loops and noise propagation.
- Linux/ALSA or
- Windows 7+, requires ASIO4ALL driver or similar to avoid sample alteration in the Windows audio path.
- Python 2.7 to run the configuration tool
- Audacity (on Windows compiled with ASIO support)