Resolution of a speed controller

[incubi]

Hi all,

I was wondering if someone has a good/simple way of doing this.

I have an AD running 0 - 255 range and I need to control a speed function with a range from 1 – 30 (no float number) so I need to scale down the AD range and still keep the full usage of the pot. I’m not sure how to do it.


incubi

[umka]

one can use something like

[incubi]

Thanks for the input

Would there be any issue with floats or because its an int will it round ok?
I know Hi-Tech has issues with that not sure about CCS.

incubi

[PCM programmer]

Divide the A/D result by a floating point scale factor, and then cast
the result to an int8. Test the results by making a loop that goes
through all the input values, and then display the result of the scaling
operation with a printf statement.

[SherpaDoug]

How about multiplying by 29, dividing by 256 (which the compiler will turn into a shift) and adding 1. These three int operations will be much faster than anything with floats, and with minuscule error.
_________________
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[incubi]

Thanks for the input that gives me some ideas to work with.

incubi

[incubi]

Just to complete this, it turns out that umka's idea was both simple and worked with no side-effects that I have been able to find. The float math and divide by 29 caused a small delay in the scanning, not sure why.

Thanks for the help.

incubi