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  • Author Author: ralphjy
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TS-04 DMM Data Plotting

ralphjy

This is a followup to my previous post: DMM Logging with Web Bluetooth .

 

I wanted to extend the HTML interface to allow me to plot the data that is received via Bluetooth from the DMM.  It seems that nowadays when I want to capture and visualize data that I'm usually using some form of IDE or dashboard in the cloud.  There are many great services out there and they are very good for analysis and generating reports.  For the purposes of a tool like a DMM I thought that it would be better to have a simpler interface that did not require internet/cloud connectivity and that could be reasonably portable.  Since I'm starting with a browser based interface I thought that I would use JavaScript libraries to do the data plotting and analysis within the HTML code.  If I use local libraries that would allow the code to be portable between computers without requiring internet connectivity.

 

First question was which plotting library to use.  I decided to try Plotly as I have used the cloud based interface and it has both JavaScript and Python libraries available.  I thought that getting things working would be fairly simple but the devil is in the details.....  Getting a basic plot working was easy but doing simple things like controlling the axes configuration is something I'm still trying to figure out.  And, of course, if you roll your own configuration - you only get what you implement (that's the good news and bad news).

 

I've now got a simple plotting interface working.  I need to work on making it more configurable but I think that's something that will happen over time.  I thought that I'd just share what I have at this point.

 

  • in reply to fmilburn

    Yes, I'm working on that next.  The original program (that Tom Igoe did) puts the decoded data in JSON format (key:value pairs), so it shouldn't be hard to store it in a CSV file.  I'll probably have to make sure I get the units right (I don't currently account for that in the plotting).  I'm still contemplating what to do about undersampling the data (it comes in at a pretty good clip).  I guess I could just set a sampling period for storage but I was thinking that I might want to retain min/max from all the data points.  I'll need to timestamp it also.

  • Hi Ralph,

     

    Nice work and a really interesting way to capture data from a DMM, and the General DMM is really inexpensive.  Would it be easy to open up a csv file and store the data for analysis?  I've not used JavaScript.

     

    Frank