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