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Computing Logarithms on Xbee 3 LTE-M

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I am setting up a device that reads a thermistor and during my conversion of the thermistor resistance to temperature, I found what appears to be the math library excluded from the library. The conversion from resistance requires computing the natural logarithm of the resistance which becomes difficult without that library.

Now I haven't consulted my Calculus book, but from what I can recall, computing that by other means is not going to be pretty and possibly more than it's worth. The other issue is that on our server end, our vendor has seemingly left logarithms out as well.

So, does anyone out there have a clean way to performing the calculation of logarithms? I was thinking I could pull a library file from somewhere and load it, but I haven't come across anything.

My other solution was to create a table or parameterize a series of polynomials, but this gets a bit messy as well. One of my other half baked ideas, was to pump the raw data and have another machine (possibly in our office) perform the computations and then send it back to our cloud platform/dashboard (I am not too worried about latentcy).
asked May 6, 2021 in XBee3 Cellular by Larry_Sellers New to the Community (10 points)

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1 Answer

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Due to firmware space constraints, the `math` module is not available in MicroPython on XBee devices. In fact, very few MicroPython ports include the `math` module. I am afraid you will need to find some other way to compute the values you need.
answered May 6, 2021 by tckr Veteran of the Digi Community (514 points)
That's what I had figured since space is constrained and the math module contains quite a bit.  I ended up generating a parametric model and it is accurate enough for what we need.  Overall I'm in that +/-1 degree C range.

Thanks for confirming!