Previously, I made a version without isolation; recently, I took some time to complete it and added the isolation protection. The sound card uses the CM108B, and the serial port uses the CH340K, with RX/TX and RTS/DTR outputs.
The audio section uses a pair of 1:1 audio isolation transformers (not yet tested).
The serial port section uses an ADUM1201-based serial port isolator. The RTS/DTR section uses a TLP2368 optocoupler. A (apparently domestic?) surface mount isolation power module provides power at 3V3.
Currently, the serial port part should be working fine (the scratch on the picture is due to the RX/TX pins of the ADUM1201 being reversed; this will be corrected in the final version of the board).
I plan to test the audio section in a few days to see if there are any issues.
The interface section uses a Type-E connector (originally intended to support both insertion directions, but found that the Type-E connector lacks a locating angle, making it impossible to insert in either direction). The official version will include wiring diagrams.
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