Can someone help me with the maths, Please!

[JPU]

Hi, thank you looking.

Im struggling with what should be simple but I cant get my head around it and I am just going around in circles. Its even harder as we cant deal in fractions!

I have an ADC input that ranges from 340 - 1000

Id like to take the input and use it to set the speed of a motor that is controlled using the pwmduty command and the range is 0-1024.

How do I take my 340 -1000 input and turn that into a value for the Pwmduty of 0 - 1024

I have come up with this bit of code but its clunky and the motor speed up has obvious incremental steps and Id like it to be more linear?

pwmout b.4,255,0

main:
Readadc10 b.5,adcvalu
adcvalu=adcvalu-340
adcvalu=adcvalu*15/10
PWMDUTY B.4,adcvalu

etc
etc

goto main

Thanks for helping as I have about given up and I am going around in circles.

JPU

 

[hippy]

It should be working without any incremental speed-ups. You could check it does work smoothly with -

Do 
  For w0 = 340 To 1024
    adcvalu=w0
    adcvalu=adcvalu-340
    adcvalu=adcvalu*15/10
    PWMDUTY B.4,adcvalu
    Pause 10
  Next
  For w0 = 1023 To 341 Step -1
    adcvalu=w0
    adcvalu=adcvalu-340
    adcvalu=adcvalu*15/10
    PWMDUTY B.4,adcvalu
    Pause 10
  Next
Loop

It would be worth using "adcvalu=adcvalu Min 340 - 340" just in case it comes in under 340.

Another alternative for your *15/10, an approximation for *1024/(1000-340) is -

adcvalu = adcvalu ** 36143 + adcvalu

 

[JPU]

Thank hippy that helped me alot.