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Pulse Width trigger problem.

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Pulse Width trigger problem.

Postby jswanson » Wed Sep 10, 2014 10:44 am

Hi,
PicoScope® 6 - PC Oscilloscope software version: 6.9.14.16
Model: PicoScope 2205 MSO
Firmware Version: 1.3.3.0 / 0.2.2.0

Trying to get the pulse width trigger to work, but it triggers all the time just as if in Simple Edge mode. Here are the settings attached.

This happened once before and it was specific to the MSO apparently. It was fixed but now it's back again.

Thanks,

Jeremy.
Attachments
Screenshot 2014-09-10 11.38.52.png
Settings
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Re: Pulse Width trigger problem.

Postby jswanson » Mon Sep 15, 2014 3:40 pm

Anyone from Pico tried this yet? Can you confirm it is a problem?
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Re: Pulse Width trigger problem.

Postby Hitesh » Tue Sep 16, 2014 8:49 am

Hi jswanson,

I've tested a setup here with a square wave (500mHz or slower, 5Vpp with +2.5V offset) using a version of PicoScope 6 that will be released shortly and can confirm that the pulse width trigger does work with the condition specified.

PS2205_MSO_pulse_width_grt_negative_pulse.png
Example of Pulse Width Trigger


The new version will be available via our Software Downloads page (http://www.picotech.com/software.html) or you will receive an alert via the PicoScope 6 software if you have enabled the appropriate option in the Updates tab of the Preferences dialog.

Regards,
Hitesh

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Re: Pulse Width trigger problem.

Postby jswanson » Tue Sep 16, 2014 9:19 am

Hi Hitesh,

I put 1s in the original as I was trying to see what values would work (nothing did).

Here is the waveform I am trying to trigger. I have triggered on this in the past, so I'm guessing it is a problem with the current version?
Attachments
Screenshot 2014-09-16 10.10.52.png
Serial Break at 250kbps
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Re: Pulse Width trigger problem.

Postby Hitesh » Tue Sep 16, 2014 1:03 pm

Hi jswanson,

I believe that is correct - an issue was found in the driver which has been fixed.

The new release of PicoScope 6 incorporating the fixed driver will be available shortly.

Regards,
Hitesh

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Re: Pulse Width trigger problem.

Postby Lotharyx » Sat Dec 06, 2014 3:46 am

Hi, I am having a pulse-width trigger problem as well, with channel D on a Pico 3405A.

If I use the onboard signal generator maxed at a 2V 1 MHz square wave fed into channel A, I can see the triggering stop if I increase the pulse width beyond 500ns. Just fine.

Unfortunately, I am trying to observe a faster signal on channel D, and it only triggers when the pulse width is set to 0 (zero).

I am trying to observe a serial binary signal which is sometimes a single high bit, and sometimes two high bits in a row, operating at around 3 MHz. In other words, sometimes the pulse is one clock cycle (about 300 ns), and sometimes it is two cycles (about 600 ns). Here are some images to help explain.

First there is short_pulse.png, which shows the short pulse of about 300 ns.
short_pulse.PNG
The shorter pulse


Then there is long_pulse.png, showing the longer pulse, about 600 ns.
long_pulse.png
The longer pulse


Finally, there is no_trigger_4ns.png, showing how the trigger doesn't occur even with a "greater than 4ns" setting.
no_trigger_4ns.PNG
Pulse width trigger set to greater than 4ns, no trigger occurs


I expect that I should be able to set to pulse width triggering around "greater than 500 ns" and the trigger occur only on the longer pulse. Unfortunately the trigger never occurs. There is a lot of ringing on the signal, but that ringing is all above the trigger threshold and shouldn't be a problem. I also tried a window pulse width, setting "dwell inside" to cover the entire ringing amplitude, and it doesn't work either. Is help available for this issue?
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Re: Pulse Width trigger problem.

Postby Hitesh » Mon Dec 08, 2014 2:43 pm

Hi Lotharyx,

There have been some issues with pulse width triggering in relation to the PicoScope 3400 devices which have recently been fixed and verified.

The fixes should appear in the next release (no timescales at present) after PicoScope 6.10.6.

In the meantime, you could try using Channels B or C for your trigger channel. Other than Channels A and D are you using any other channels?

Regards,
Hitesh

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Re: Pulse Width trigger problem.

Postby Lotharyx » Tue Dec 09, 2014 3:28 am

Hi, and thanks for the rapid engagement. I really appreciate that.

It seems like using another channel on the same signal allows the pulse width trigger mode to function correctly, so perhaps the problem is unique to channel D.

I have moved on to other modes of testing which do not rely on the pulse width triggering, but I still look forward to PicoScope software and driver updates.
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Re: Pulse Width trigger problem.

Postby HMD » Mon Jul 06, 2015 10:09 am

Hello,

I found a(nother) bug in the Advanced Trigger Menu “Pulse Width” for digital inputs (D1/D0) . If I try to trigger for a Pulse Width greater than 20 ms on a digital input (D1). The Oscilloscope triggers always.
But the pulse width is less than 5ms.
My digital signal channel settings are correct: (Signal is TTL 3.3V high)
For analog signals e.g. A/B everything works fine.

SW versions: PicoScope® 6 - PC Oscilloscope software version: 6.11.4.929 and 6.10.16.2
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Re: Pulse Width trigger problem.

Postby Hitesh » Mon Jul 06, 2015 10:50 am

Hi HMD,

There was an issue relating to pulse width triggering on digital channels that was reported and fixed recently. This should be available via the next version of PicoScope 6.11 Beta.

If you have a PicoScope 6 settings file corresponding to the trigger setup, please post it here or send to support@picotech.com and we can take a look.

Regards,
Hitesh

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