Jan,
In the "good old days", you could check a serial port by connecting pin
2 to pin3 at the end of the serial cable. Set the port to software
handshaking (or else connect the control pins together in a similar
manner-I don't recall the pin numbers). Then run a dumb terminal
program. What you type will be echoed to your screen, even with "echo"
turned off. If echo is turned on, you'd see what you typed twice. That
would prove the signal made it out and back and the interface works.
The baudrate doesn't matter, as long as it's the same for transmitting
and receiving.
73,
John AA0VE
Jan,
The best way to test a USB to serial converter is by substitution with
a known good one, or by substitution of a known good working serial
device connected to the questionable converter cable.
Yes, a power surge or a lightning event can damage serial interfaces
as well as USB interfaces.
Since your USB ports on the computer seem to work, borrow a known good
USB to serial converter and try it out - preferably one with an FTDI
chipset.
If you have any other devices that use a serial COM port interface,
see if they work with your USB to serial adapter - if so, the adapter
is probably OK, but remember that in the event of a power surge,
multiple failures are possible even though in normal troubleshooting
we assume only a single failure.
You can test the USB to serial converter with a 'scope and an RS-232
breakout box, but you have to know the proper RS-232 levels to
understand what is happening. A null modem loopback cable can be
helpful if you have to proper driving software application for that
testing. I did that during my years of PC modem testing, but that was
more than 30 years ago and the software ran under DOS - not helpful now.
73,
Don W3FPR
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