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adc100 strange behaviour when recording from both channels

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adc100 strange behaviour when recording from both channels

Postby WilliamMc » Tue May 24, 2005 11:36 am

I'm recording eye movement data (represented as a DC voltage from a Skalar Iris tracker) using the adc100. Channel A is used to record horizontal position (voltage) and B used to record vertical position (voltage).

When I record from just one channel (A or B), everything looks fine. But when I record from both channels, there is a weird crosstalk between them. At irregular intervals, some voltage is subtracted from the A channel and added to the B channel, and/or vice versa.

What the h*ll is going on? I have psd traces of this behaviour from picoscope if you want to see them.

The adc100 is being read thru LPT1, with the adapter and win.ini is set up fine.
WilliamMc
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Postby Sarah » Wed May 25, 2005 8:33 am

Hi

Thank you for your post, I am sorry to hear that you have been seeing this problem.

Is this with Picolog? I am aware of a bug in the current version of Picolog which has this effect on readings. I would recommend trying the older version 5.11.8 which you can download from our website at:

http://www.picotech.com/software-archive.html

Let me know if this helps.

Best Regards
Sarah
 

adc100 weirdness

Postby WilliamMc » Thu May 26, 2005 10:01 am

Not with picolog, the problem is with picoscope, latest version (on the r.20 cd) and also with a mex file interface to matlab, using an older version of the adc dll's. Both setups have the same difficulty - fine with one channel, weird crosstalk of kind-of ac & dc with two channels.
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usb ok

Postby WilliamMc » Thu May 26, 2005 12:19 pm

Just had some time to muck about.

Used the usb connector thru a belkin usb pcmcia-card (needed because the built-in usb ports on this computer are cheap&nasty, don't work with many usb peripherals) and picoscope can read good signals from adc100, without the weird crosstalk. So problem is in lpt1, maybe bios settings need to be changed.

However...(no happy endings for me)

When I tried to access the usb port (it's usb port 1) using the supplied visual basic example, with port=101, it was unable to connect to the port, and returned failure. This is important, since I need to read the adc100 outputs in my own program.

In addition, it takes a long time (maybe a minute) for picoscope to connect to the adc100 via usb, and when the VB example fails to connect, picoscope will also fail to connect until the usb cable is unplugged and replugged.

Any ideas? Is picoscope just more persistent about looking for a connection?
WilliamMc
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Postby Sarah » Fri May 27, 2005 10:58 am

Hi

Thank you for your post.

You may have to increase the length of time the examples are taking to look for a response, if it is not responding quickly.

This is not an issue I have come across more so I will need to look into it. If you can provide me with further information then that would help me in trying to replicate it.

Best Regards
Sarah
 

Postby Guest » Fri May 27, 2005 11:30 am

OK, I gave up on using that computer because of the various problems encountered. The original problem must have been due to the printer port, which on that computer can only be set to EPP/ECP/Bidirectional, none of which are suitable for adc100. And the USB interface is just too annoying to perservere with.

So I dusted off an old Dell workstation. This has a good LPT1 port that can be setup correctly to interface to the ADC100.

Dell runs win2K; printer port adapter is used. [ADC100]UseAdapter=yes is in win.ini

Here's what happens, using R.20 software/drivers

Picoscope - no problems initially. Gives good readings.
VB example code - usually works, but sometimes complains that it can't find pico.sys.
C code - (this dynamically loads the adc100 dll, so it always uses the latest version) sometimes complains that it can't find pico.sys; however, depending on where this C code is called from within Matlab, sometimes pico.sys is never found. In addition, the code, which previously reported scaled voltages, now reports unscaled integers (now that's a bizarre change, since the C code has not been recompiled)

Once pico.sys is lost, it stays lost for a while. Usually restarting picoscope is enough to refind the lost pico.sys file, but not always.

I noticed a similar problem on another forum post, where pico.sys wasn't found, and you suggested using the latest software. This I have.

Suggestions please?
Guest
 


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