VT340 Emulation

Ethan Dicks ethan.dicks at gmail.com
Tue Jun 22 10:12:17 CDT 2021

On Tue, Jun 22, 2021 at 6:32 AM Grant Taylor via cctalk
<cctalk at classiccmp.org> wrote:
> > I would love to see REAL RS232 on a RBPi, probably even the original
> > MMJ from DEC for keyboard & mouse
> What is a /real/ RS-232?  How does it differ from USB-to-RS-232 and / or
> bit banging GPIO lines?

The OP said he meant with "real" connectors, but in my case, I've
encountered strange buffering issues with USB serial dongles (since
they are really block-mode devices, not character-at-a-time) and I've
definitely had problems supporting lines with odd parameters
(especially speeds slower than 300 baud or with 5-bits-per-char, like
one would use for a Model 19 or Model 28 teletype).  The hardware
UARTs on AVR processors implement those juse fine (though for "50
baud", you often have to put a slower crystal on the processor because
the 16-bit divisor overflows at 16-20MHz).  The "soft serial"
libraries often just hard-code 8-bit implementations.  Fine for modern
stuff but I have uses for connecting to electromechanical serial

In terms of a CRT terminal, though, most modern serial implementations are fine.


More information about the cctalk mailing list