24 Jun
2019
24 Jun
'19
7:40 a.m.
On Sun, 23 Jun 2019 20:53:19 -0400 Arthur Krewat <krewat(a)kilonet.net> wrote:
Both the AT&T and the USB cable will be
"DTE" (Data Terminal Equipment -
ala terminal) vs. "DCE" (Data Communication Equipment - ala modem) -
you'll need a null-modem cable to correct that mismatch. Basically, if
not using hardware handshake, swap pin 2 and 3. ;)
Since mid 80s I have used Dave Yost's wiring scheme that
converts a DB-25 or DB-9 adapter to an RJ-45 socket:
http://yost.com/computers/RJ45-serial/
You wire any DB-25 or DB-9 DCE or DTE male or female adapter
so that the RJ-45 socket has the above pinout. You figure
out which device needs what kind of adapter and permanently
attach the adapter. Now you can use a standard "half-twist"
phone cable with 4, 6 or 8 wires and connect anything to
anything.
My last device with a real RS-232 interface (a CP-290 X10
controller) where I used this died 4-5 years ago. I still use
serial ports on RaspberryPis but talk to them via serial<->USB
adapters (these are 3.3V uarts).