Serial Connection Cable

[1337Hendrix]

So, I'm working on troubleshooting a timing delay in my lab.

Long story short, there seems to be a discrepancy in the time the Recording PC receives the Stimulus PC's message to record the waves from the EGG amplifier, and the time the signal is received to start the condition.

So, basically, we are not recording the first few parts of the post stimulus waveform, which are consequently the most important in the studies we want to run.

I want to record the signal directly from the serial connection cable when it is sent out, because even when we time stamp the signal on the E-prime software, its variability is too high to actually make any sense of it.

If I can record it physically, I can determine the exact real life time difference between the stim-record signal and the stim-condition signal.

So here is where I need your help:

If I were to get a new cable, chop it in half, and record the voltages, I should be recording at the open wire end...right? Or should I measure the voltages at the other end of the serial connection cable, you know, like at the pins?

Could I perhaps rig the cable, either by stripping the wire but even better to just buy a connector, to a stereo system, and record the onsets of the digital signal and the analog condition signal?

Is there anything else I should be taking into account?

Thanks guys!

[toraton]

I suppose I don't understand why you can't monitor this with a mic line. Just record the waves as they come in.

[1337Hendrix]

Well, that's one of my problems, how I can I connect a serial connector to a mic line easily?

That is why I need to buy a converter for the serial cable I guess, or strip down the wire to attach it to some sort of audio component. But i need a serial to audio converter piece if I don't want to gut the thing.

I figure I can find the wire that is "Data out" and hook that up to like a stereo or even something that will plug into the computer and record the signal like that.

I did not have time to actually go mess around in there today, but I from what I remember, the connectors on the cable were RS232 DB 25.

I found a pinout diagram on the web also.

I can also use a breakout box to test all the connections, or I can use Checkit Diagnostics. The only thing is, I'm not too familiar with the box, or the software and not sure if there is any time stamp options, to avoid stripping the wire.

[1337Hendrix]

I'm thinking something along the lines of this:

http://www.k6xx.com/radio/ft857ser.pdf

Can't seem to find where to get my hands on one though, but something a bit more direct would be nice. Perhaps something I could plug directly into the back panel of the computer tower.

Anybody??

Making my own cable is not something I want to do if I can just purchase a part/cable.