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Open Logger : Function Gen issue ..


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I was trying to generate a Sine and Square wave using the FG functionality in the Open Logger.  A few observations :

1. I chose a Sinewave of 1V pk-pk and 50Hz to simulate a mains frequency sampling.  I then fed this signal to AIN1 channel. But was surprised to see that the pk-pk was far less than 1V. It actually was around 0.6V. Tried other voltages also but the result was same. Not sure why. 

2. I then tried a low frequency square wave and what i got was not anywhere near a square wave -- it had pretty rounded rise and fall edges. 

Is the above due to the fact that this board does not use a DAC but only a resistor network instead ? Or I am missing some setting ??

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Hi @Raghunathan,

Could you attach a picture of your settings? I was unable to replicate the situation regarding the peak to peak voltage (my screenshot is using 50 Hz, but 60 Hz did the same as well).

With regards to the square wave appearing curved, I was only able to see this when I zoomed in so that the time base was at 2 uS/division or less but at that point you are just viewing the output settling time of the requested change which should be about 580 nS as noted on slide 91 on the detailed Microchip Masters Presentation.

Thanks,
JColvin

1V p2p view.png

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Thanks Colvin !

After I posted and shut down the system and re-started all things fell in place.  Possibly in the first instance I was changing too many parameters on the fly with both Streaming and WavGen running and the system became unstable. 

Now its fine.

I would like to make make all my settings on the right side as Default settings to be pulled up when the WaveForms live loads .. I think Profiles are stored in flash. Will selecting Log on Booting do that  ? 

Also I get a "Error Starting or Running " if I try to log to a SD Card. Its a Sandisk 32GB MicroSD formatted for FAT32.  The filename is there but filled with gibberish. 

Edited by Raghunathan
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Hi @Raghunathan,

I apologize for the delay.

My understanding is that the profiles are stored in the flash memory. I'm not sure how the Log on Boot works, but I believe when it is enabled it saves the current parameters as they are currently set to a profile which it then uses as per this comment: https://forum.digilentinc.com/topic/18986-can-openlogger-work-standalone/?tab=comments#comment-50787.

I'm not sure on the "Error Starting or Running" for the SD card; I'll ask the engineer more familiar with this when they get back into the office next week. The formatting and size is correct. Though the file will need to be converted into a CSV data which has some more details on this post here.

Let me know if you have any questions.

Thanks,
JColvin

 

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Hi Colvin

That was news to know the Open logger can work in standalone mode and the Log on Boot now makes sense. So it being a "blind logger " with no display, I will now have to depend on the WiFi to really know if its logging anything to the SD card. 

Now in both the boards that I have,  both SD card and Wifi keep doing funny things and impossible message boxes and so it saves me lots of trouble trying to finger them !!  This link is dead https://forum.digilentinc.com/topic/18263-openscope-and-openlogger-log-file-utility-export-to-csv/?do=findComment&comment=50627

 

I read through the  posts you linked and see that for all practical purposes the Open Logger project development is over. Does not feel good for a crowd funded project and supported by Digilent

Thanks so much for trying to help. 

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  • 2 weeks later...

Hi Andrew,

Ok once I knew that the logging is in binary format, I gave up trying even. I should either have a converter that works or logging should happen in a CSV file.  Anyway the file export works nicely and I am happy with it. 

After my last few posts I have been spending time  with the open logger and it has now come to terms with me and is listening to my commands !   WiFi link is working. I can save logging profiles. And recall profiles. 

Anyway the Function Gen settings are not getting saved to profiles but that is OK. Can manage. 

And when something acts funny , a power cycling generally makes the module behave.

But if I were to voice my thought : A function filled module as Openlogger should have been delivered with a customized software instead of depending on the generic WFL.  Maybe its cost effective but also has a steep learning curve. 

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