Scaling ADC values

[purkolator]

Thanks for the help Skimask, it helped a lot. I used your method with a couple of modifications and it seems to work very well.

First, I added to your method was to define minimums and maximums. I was having problems bumps/shakes of the accelerometer making the min and max values go well outside of the range which I wanted to capture (which is neutral to 90 degrees on either axis). The MIN and MAX statements solved that.

I also added a line to subtract the minimum value from the capture adc value. This ensured that the final output was actually 0-127. Without it, my output would never go all the way down to 0.

In the long run (as I am sure many of you will notice) I will probably just define range since I know what the adc values are at +90 and -90 degrees. I haven't done that yet, because I want to be sure that environmental variables don't affect the accelerometer output.

Here is the routine that I ended up using....


modcheck:
ADCIN 1,modval ' Read channel 1 to modval
modval=modval min 166
modval=modval max 91
if modval<minval then minval=modval
if modval>maxval then maxval=modval
range=maxval-minval
modval=modval-minval
scalefactor=65535/range
modvalnew=modval*scalefactor
modvalnew=modvalnew>>9

[skimask]

One thing I forgot to mention (but it seems you already took care of it in a way) is to initially set your minimum value very high (so the only place it can go is down) and your maximum value very low (so the only place it can go is up)...

[RodSTAR]

One thing I forgot to mention (but it seems you already took care of it in a way) is to initially set your minimum value very high (so the only place it can go is down) and your maximum value very low (so the only place it can go is up)...

yes, both near the center