Problem: corrupted output signal on channel 2 in jupyter

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Hinkestein
Posts: 5
Joined: Wed Oct 14, 2015 9:54 pm

Problem: corrupted output signal on channel 2 in jupyter

Post by Hinkestein » Fri Sep 22, 2017 8:41 pm

I installed the new latest 0.98 stable image and tried the jupyter examples.

When I run examples/gen_sync_two_channel.ipynb I get a pretty spot on sine wave on channel 1, but a heavily distorted signal on channel 2.
(see attached screenshots from my scope)

I noticed by playing around with the phase value that
gen1.phase = 0 (instead of the 90 degree value)
makes it even more worse!

At first I suspected a problem with the output of channel 2, but I verified the same behaviour on my second RedPitaya board. :(
Another observation: the signal generator of the standard scope app works perfect on both channels.

Whats gone wrong here?

Best regards
Gunther
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Hinkestein
Posts: 5
Joined: Wed Oct 14, 2015 9:54 pm

Re: Problem: corrupted output signal on channel 2 in jupyter

Post by Hinkestein » Fri Sep 22, 2017 8:55 pm

same with examples/generator_widget.ipynb:
channel 1 ok, channel 2 garbage output.
here also the values of the frequency sliders are completely wrong.

Hinkestein
Posts: 5
Joined: Wed Oct 14, 2015 9:54 pm

Re: Problem: corrupted output signal on channel 2 in jupyter

Post by Hinkestein » Fri Sep 22, 2017 9:09 pm

scope-app_2ch-input_from_fg.png
at least you can see this behaviour even in the scope-widget :shock:
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amike88
Posts: 78
Joined: Tue Mar 29, 2016 7:41 pm

Re: Problem: corrupted output signal on channel 2 in jupyter

Post by amike88 » Thu Oct 05, 2017 12:36 pm

Hi,

i've just tried this example "examples/gen_sync_two_channel.ipynb" and as can be seen in the picture bellow it seems to work for me.

This is just an idea, but have you checked your connector cables?
Otherwise I'd recommend that you download a clean image from RP download server and make a clean SD image with it (I'd recommend etcher), perhaps something went wrong with the upgrade.
20171005_131716-small.jpg
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Hinkestein
Posts: 5
Joined: Wed Oct 14, 2015 9:54 pm

New observations

Post by Hinkestein » Fri Oct 20, 2017 6:44 pm

tried a clean install, same effect. :(

BUT I noticed something interesting:
I connected the input and output channels together, rebooted and started Jupyter.
Then I started the Scope Widget (examples/oscilloscope_widget.ipynb) and the Generator Widget (examples/generator_widget.ipynb)

Now when I turn on output channel 1 I see the expected waveform on input channel 1.
BUT I also see a square wave on output channel 2 !!!!!

Enabling the second output channel then garbles the output again.
(looks like an addition of both signals, the square wave and the sine, with some distortions added)

Does anyone else see this?

Btw: I have a version V1.0 board from the kickstarter campaign.
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Hinkestein
Posts: 5
Joined: Wed Oct 14, 2015 9:54 pm

There IS a difference between boards! :( :( :(

Post by Hinkestein » Sun Apr 29, 2018 10:12 pm

I invested in a new Redpitaya STEM 14 board and tried to verify the mentioned behaviour.

To my big surprise the output on the new board is correct as expected, but with the identical SD-card in one of the old boards, I still get corrupted output on channel 2!

OS-version: Red Pitaya OS 0.98-617 / STEM 14

Below I added the IPython-notebook I used for testing. (just delete the "txt"-extension after downloading)

I also added a photo of the 2 boards and 2 screenshots from my scope.

As you can see from the photo, the probes on the scope are connected in this order:
CH1 (yellow) is OUT1 on the new board STEM125-14 V1.0
CH2 (green) is OUT2 on the new board
CH3 (magenta) is OUT1 on the Kickstarter V1.0 board
CH4 (cyan) is OUT2 on the Kickstarter V1.0 board

"after[10].png" shows the 2 outputs of both boards after executing block [10], which turns on the arb output on channel 1.
"after[11].png" shows the 2 outputs of both boards after executing block [10], which turns on the arb output on channel 2.

As it can be seen it seems that the V1.0 board outputs a rectangle signal on OUT2 as soon as OUT1 arb generator is enabled. This is not the case with the new board.

At the moment I'm pretty annoyed that I had to invest into a new board just to verify my suspicions.... :(
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