PIC Controller for Multiply and Division?

[Sajjadkhan]

I want to monitor remaining battery capacity by measuring and keeping record of its in/out charge current given the battery capacity. That requires floating point calculations. I have seen PIC24 series architecture and one of its block says "Hardware multiply and division". Had anyone any experience with that?

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[keith1200rs]

You don't necessarily need to use floating point for most of the calculations if you scale the numbers. If you are using C then all the hard work is done for you anyway, even if you use an 8 bit PIC. The only thing you need to watch out for is how long the calculations take. From memory a 16*16 multiply with 32 bit result is done in a single instruction cycle and divides are around 18 cycles. If the numbers are 32 bit or floating point it will take longer. I am not sure if there are times given in the C compiler help but if not you will need to benchmark it. Provided you have some 'dead time' in which to do the calculations I doubt it will be a problem with a PIC24.

Keith

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By the way, my PIC24 experience is mostly the E and H versions but I think the F versions are similar - just slower clocks,

 

[babar_ali]

Hi,

You did not mentioned what sort of battery it is and how much is the capacity. How are you charging and discharging. There are a lot of IC's for this purpose. Gas Guage IC's from TI (BQ2010 that I worked with) are available. These IC's have the tendency to calculate the charge and discharge rate and also take care of the battery temperature.
Enjoy!