Issue with Talons

[Ether]

Originally Posted by RyanN

As scary as it sounds, you can also use a computer's line-in port and Audacity to take in a waveform.

True. I've been meaning to try that sometime. I use Audacity all the time for ripping my old collection of cassette tapes.

You'll want to use a voltage divider to limit the voltage going into your PC as to not fry your sound card, but it's doable and works pretty well in my experience.
http://www.ledametrix.com/oscope/index.html

What's the input impedance of a typical sound card, do you know? It looks like he's got the voltage divider bass-ackwards. He said he wanted to divide his 5-volt input down to 1 or 2 volts.

Food for thought:
If all you are trying to do is measure the timing (not observe the waveform) of a digital signal then you don't need the sound card's ADC. All you want is to capture and timestamp the edges. The parallel port works great for this. You can poll the data pins of a parallel port at 680KHz or so... way beyond the frequency of the audio card.

[KrazyCarl92]

So here's an update with what we tried tonight:

At first we started driving the robot around and did not observe the problem. Then, within 10 minutes the issue started back up again with the same symptoms as before. The robot twitches to the right before driving forward or reverse when it is command to go at high speeds.

To describe the trouble shooting and results we got, I will use the terms "DSC A" and "Cable A" to describe the equipment we started with, and "DSC B" and "Cable B" to describe the components we tried switching out with.

First we switched the cable from Cable A to Cable B since this was the easiest switch. The problem got worse. Now when enabled, the robot just ignored our commands and abruptly twitched turning to the right continuously.

We then tried the original components and got back to square one. Next we tried DSC B with Cable A and the problem seemed to be remedied, but we were unconvinced because we now thought that the problem could be with the cables since it seemed to be significantly worse with Cable B as compared to Cable A when both were paired with DSC A.

When we tried DSC B and Cable B together, we got the same exact symptoms as DSC A and Cable A; the robot does a single twitch to the right before driving forward when commanded to only go forward.

So we went back to DSC B and Cable A since this got us the best results. And after about 15 minutes of driving that way, we have yet to reproduce the problem. I'm hesitant to say that the problem is fixed because the logic is very odd and we haven't tested extensively yet, but the symptoms of the issue have yet to be observed in this configuration.

Can anyone else follow this or make any sense about what these results could mean? Maybe both DSC A and Cable B are bad, but I would expect more sensible results in that case...