Isolated TTL USB UART

I designed an RS-232 adapter and posted it over at the original non-isolated variant page. It also works on this isolated version, and the net result is a galvanically isolated USB to RS-232 adapter.

The first prototype works flawlessly, so far as I can tell (with the proviso that DCD and RI are not connected because I don't have any SI8055s and there won't be any until August).

Sigh.

I have some SI8035s left over from my development of the USB Isolated null modem.

But I don't have any SI8055s on hand... and now they're backordered until August. None of the SI80xx line are on hand anywhere. We can't have nice things.

For prototyping purposes, I can use a 35 to replace the 55. Doing so means that DCD and RI will fail to work, but it's a start.

EDIT: I found a few of these on AliExpress and have enough on hand for now.