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2205 MSO Data acquistion anomalies

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2205 MSO Data acquistion anomalies

Postby Graybags » Thu Jan 09, 2014 4:09 pm

Hi,
I'm just 'playing' with a new 2205MSO and I think I've found a bit of a problem using the Digital Channels.
Of course it may just be my understanding.
Set up is simple 555 timer about 740Hz as Clock driving two asynchronous 4 bit counters.
ChA x10 connected to Clock. D7-D0 to outputs of counters, organized as a single group.
Trigger: Single, Digital: Binary 0000000R, Pre Trig 50%
Number of Samples: 49.08 kS (Default)

At 1ms/div: OK (ChA shows number of cycles and Group counts exactly as expected FD FE FF 00 01 02 03 04)
At 100uS/div: Also OK (ChA has single rising edge Group 00 01)
At 50uS and 20uS: As above.
At 10uS: ChA still OK - but Group is completely incorrect (see attachment #1).
It appears as if the data buffer has 'random' data in the range -50.0 - -31.8uS the remainder of the buffer is all zeros's.
The clock edge on ChA is perfect.
Changing the trigger to Digital: Binary 0000011R etc does not change the results??
10uS_div.psdata
Attachment #1
(13.88 KiB) Downloaded 63 times


For all time/div from 5uS down to 50nS ChA reveals increasing slope to the rising edge (as expected) Group 1 remains at all zeros's.

If this is repeated, but the trigger is changed
Trigger: Single, ChA Rising 2V Simple (Thus it should trigger on any group value 1:256 chance)
Then the 20uS/Div again seems to limit the expected behaviour - at this and above group values are random, but always in sequence changing at the trigger point.
At 10uS/Div and below the above incorrect behaviour is repeated group value remains stubbornly at zero.

Thanks
GB

<Edit> 14/1/2014
I've noticed that my version of Picoscope (via Help) is 6.7.35.1
I'm also running on Windows 8.1 x64
Help/Check for updates responds with 'There are currently no software updates available'

However, browsing the web-site reveals several updates since this version, many with anonymous 'bug fixes'...

So - should I try a particular version? If so which (obviously the latest is a prime candidate).
Can you just install the new version on top of the old or is it best to remove the old installation first?
Thanks
GB
</Edit>
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Re: 2205 MSO Data acquistion anomalies

Postby Martyn » Tue Jan 14, 2014 11:34 am

I would suggest trying with 6.8.6 RC, this is a Release Candidate which will become the stable release very soon.
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Re: 2205 MSO Data acquistion anomalies

Postby Graybags » Tue Jan 14, 2014 1:34 pm

I try with the candidate release as you suggest.

Considering I'm on Windows 8.1 - what is the best proceedure.
Will they co-exist side by side?
Just install new version?
Uninstall old version then install new version?
Or is there a preferred update mechanism?

Thanks
GB
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Re: 2205 MSO Data acquistion anomalies

Postby Martyn » Tue Jan 14, 2014 1:37 pm

Install over the top should be fine, that is the way the automatic update mechanism works. This version isn't treated as an automatic update as it is a Release Candidate.
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Re: 2205 MSO Data acquistion anomalies

Postby Graybags » Wed Jan 22, 2014 7:28 pm

Hi,
Apologies for the delay - seconded to another project.

I've now installed Picoscope version 6.8.6.9 and the problem remains.
In addition I've tried setting the Collection Time to 10uS/div and adjusting the Pre-trigger - this has interesting results.

The analogue chanA rising edge 'moves' as expected in response to the changes in pre-trigger - but the ringing in the digital channels D7-D0 subbornly stays put - taking up the first 18% of the display. Pedantically 18.71uS at this time/div.

At faster time/div the D7-D0 value is 0x00 for the whole record.

Attached are some more samples - are you seeing the same as seen in the pdf?
Am I the only one seeing this?

Thanks
GB
Attachments
10uS_per_div.pdf
(129.26 KiB) Downloaded 49 times
10uS_div_10pretrig.psdata
(10.01 KiB) Downloaded 43 times
10uS_div_90pretrig.psdata
(12.04 KiB) Downloaded 60 times
10uS_div_50pretrig.psdata
(10.68 KiB) Downloaded 62 times
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Re: 2205 MSO Data acquistion anomalies

Postby Martyn » Mon Jan 27, 2014 12:22 pm

I have reported this to the development team, it appears to be linked with the maximum sample rate.

In the meantime if you reduce the number of samples to 10ks it should work normally.
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Re: 2205 MSO Data acquistion anomalies

Postby Graybags » Tue Jan 28, 2014 3:48 pm

Hi Martyn,

Yes that has solved the problem.
Thanks very much for your help.

Just FYI I've also repeated the tests using both analog channels as well as D0-D7 and this appears to fix the issue too.
Furthermore it also cures the loss of digital data at speeds above 10uS/div. This may be related to using digital triggering. A simple test for this is to use a simple counter and trigger on 0xCC say (value irrelevant). At slower speeds all Ok as we've said, at higher speeds the problem exists. Turn on ChB and it's fixed at all speeds.
Simply toggling ChB on/off and the problem appears/disappears.
Strangely keeping ChB on and toggling ChA has a different result - it works at all speeds? Which implies it's something in the setup of ChA...
Hope this helps the dev team.

Thanks
GB
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