It seems to me IBM does something weird with the printer ports too. I
tried using my ThinkPad I got back in 2000 as a lap timer for slot
cars and had all sorts of problems. Ended up just getting a cheap
desktop and putting that on.
I have had really good luck with the Keyspan USB-RS-232 dongles though.
Randy Rathbun, NV0U
K2 #1981
[EMAIL PROTECTED]
On Jun 13, 2005, at 7:56 PM, VR2BrettGraham wrote:
N0SS continued:
Well, I think I've found the culprit of my K2 serial comms
problem... and
it's the laptop!!! Unfortunately!
My IBM ThinkPad 380D shown the following voltages:
Voltages:
TXD line (from K2PA100):
Quiescent: -15VDC
Sending data: +5VDC
RXD line (from IBM ThinkPad 380D):
Quiescent: -5VDC
Sending Data: +1.0VDC
Given data provided by Jack Brindle, W6FB, the TXD line appears to
be about
1.4VDC under the minimum required voltage.
That is likely to remain flaky.
I can't find my copy of EIA/TIA-232-F, but ITU-T V.28 mentions the 3
volts as the minimum that I always remember.
5 volts may be what a driver should produce, as I did find some
mention
of 2 volts allowance for noise at the far end.
Interesting - the usual culprit is something to do with a software
driver, as had been suggested. Now is this some sort of intermittent
hardware fault, or could it be that one can't assume that an IBM
ThinkPad's RS-232 port(s) don't do real RS-232? I was counting on
getting a ThinkPad as it's on of the few decent laptops that can still
be had with a real serial port!
Speaking of serial control of the K2, a few months ago I was looking
at the chirp (cricket sound when polled for frequency data by a
computer) & the data received by the K2 does get serious radiated by
the ribbon cable - though no amount of dressing of the cable made a
difference, suggesting rather than induced by the ribbon into
surrounding circuitry, it's induced into the lines in the ribbon
itself
(power?).
Have a look with a 'scope probe around the ribbon & note the
difference in RXD & TXD-induced spikes coming from the ribbon.
Anybody have any idea why RS232-in-converted-to-TTL should
be worse than TTL-converted-into-RS232-out?
73, VR2BrettGraham
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