On Wednesday 28 April 2004 19:14, John Allain wrote:
> > Does it contain RS232 level shifters, or are
> > the signals on the socket at TTL levels?
>
> No clue.
> I do have a O'Scope handy, but a rather useseless
> brain as regards to applying said O'Scope. An instruction
> or two would help. Am I looking for 5v vs 15v signals?
Step 1. Grab DMM/VOM. It's much easier to check voltages with
(assuming the serial port is normally inactive).
Step 2. Either tip or ring will be your output. A cable like a
1/8" (mini) to dual RCA "splitter" cable should give you those
on the RCA connector centers. Check center to ground on both
if you get 10-15V on one, you've got RS-232, and it's your output.
If you get about 5V, it's TTL, and your output.
If you get < 1V, it's probably the input, but could be a TTL output.
If both lines give you <1V, stick your DMM/VOM into resistance mode,
and check resistance between the lines with the device on. This is
safer with a DMM as it'll use a lower voltage to test with. The
line with the lower resistance is the output (probably 1kohm or less);
the line with the higher resistance is the input ( probably >=10kohm).
In any case, it's TTL not RS/232 if you don't measure +-/- 10-15V.
Make sure you check both connectors to be sure.
Pat
--
Purdue University ITAP/RCS --- http://www.itap.purdue.edu/rcs/
The Computer Refuge --- http://computer-refuge.org
Received on Wed Apr 28 2004 - 20:27:14 BST