Has anyone built the hardware for Zimodem?

Hi, All (but especially, Bo)

I was looking at fiddling with a WiFi modem project this year and it
didn't take long to discover Zimodem.


https://github.com/bozimmerman/Zimodem

The source is all there, there's a good summary of the command set,
but what I could not find was anything to do with construction.  I
know how C-64 RS-232 works and can go through the sources to figure
out what pins are what pins, but this will be my first ESP8266 project
and beyond knowing about 3.3V PSU and I/O, I'd like to start with the
benefit of anybody's experience with this build.  In particular, since
one of my targets is the C-64 (and eventually the 8032) I'm going to
start with a CBM edge connector rather than a full DB-25 RS-232
interface and I'd like to know about what inexpensive options work for
3.3V<->5V level converters.  It's low-speed, so I would _think_ that
simple passive voltage dividers would be fast enough vs IC-based level
shifters, but I'd like to hear that from someone that has done it.

My eventual plan is to come up with an inexpensive build list to make
construction a small pile of these affordable to be able to take them
to a vintage computing event (like VCF Midwest) and loan them out and
not worry if they don't come back.  The point being to allow anyone
present to connect to an on-site BBS during the event.

Thanks for any suggestions.

-ethan

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