72 lines
3.4 KiB
Markdown
72 lines
3.4 KiB
Markdown
# ADAT USB Audio Interface
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FPGA based USB 2.0 High Speed audio interface featuring multiple optical ADAT inputs and outputs
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## Status / current limitations
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* Enumerates as class compliant audio device on Windows and Linux (Mac OS not tested). 2 and 32 channel modes.
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* Audio input and output seems to work glitch free.
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* Only 48kHz sample rate supported
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* Integrated USB2 high speed logic analyzer works
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* Runs without dropouts with FlexASIO with a buffer size of 32 samples (0.67ms latency)
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* Has a hardware roundtrip latency (USB out -> ADAT out -> cable -> ADAT in -> USB in)
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of 2-3 USB2 microframes which is about 0.25ms to 0.375 ms
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* Both headphone DACs on the board work now. In two channel mode, they are both wired to channels 0/1.
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In 36 channel mode DAC1 is wired to channels 0/1 and DAC2 to channels 2/3
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* Both USB PHYs now are operational. USB1 has access to all 32 ADAT I/Os and has 4 extra channels to/from USB2.
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USB2 enumerates as a 4-channel sound card which sends/receives audio to/from USB1
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* Both USB interfaces will also enumerate as USB MIDI devices and send each other MIDI
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* The current board design has not been designed with the case in mind: In the current version of the case,
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only ADAT-cables with thin connectors will fit into the holes. Cables with fat connectors will hit the case
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wall before they can be fully inserted. This will be fixed in a future iteration of the PCB and case.
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* The current case design lacks a guide channel for the LED light pipes. Therefore there is considerable bleed
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from lightpipes into each other, and they also can't be positioned exactly over the LEDs.
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Will be fixed in the next version of the case.
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* Limitation: Currently audio input will not work properly when audio output is inactive.
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This should not be a problem for most uses (VoIP, Videoconference, DAW recording).
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If you have an important use case which needs this, please file an issue.
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## Hardware
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The current board design is a custom development board,
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based on the QMTech core FPGA boards.
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Once the chip shortage is over, it is planned to move to
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a complete custom design, including the FPGA.
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## How to build
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1. Download and install [Intel Quartus Lite](https://fpgasoftware.intel.com/?edition=lite)
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2. put the bin/ directory of Quartus into your PATH variable:
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```bash
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export PATH=$PATH:/opt/intelFPGA_lite/21.1/quartus/bin/
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```
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Of course you need to adjust this to the install directory and version of your particular installation.
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3. Set up python venv and install requirements:
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```bash
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$ cd gateware/
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$ ./initialize-python-environment.sh
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$ cd ..
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```
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4. Activate the venv and build
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```bash
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$ source ./gateware/venv/bin/activate
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$ python3 gateware/adat_usb2_audio_interface.py --keep
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```
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This will create a directory named build/ and after a successful build will directly
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try to load the generated bitstream into the FPGA, if an USB-Blaster is connected.
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Or, you can flash the bitstream manually, by opening the Quartus GUI with:
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```bash
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quartus build/*.qpf
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```
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and then open the programmer application from there.
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Alternatively you could directly start the programmer with:
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```bash
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quartus_pgmw
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```
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