[Elecraft] KIO2/KPA100 Serial Comm Problems

[Randy Rathbun]

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
randy at randyrathbun.org


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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