View Single Post
  #1   Spotlight this post!  
Unread 25-01-2010, 03:21
jhersh jhersh is offline
National Instruments
AKA: Joe Hershberger
FRC #2468 (Appreciate)
Team Role: Mentor
 
Join Date: May 2008
Rookie Year: 1997
Location: Austin, TX
Posts: 1,006
jhersh has a reputation beyond reputejhersh has a reputation beyond reputejhersh has a reputation beyond reputejhersh has a reputation beyond reputejhersh has a reputation beyond reputejhersh has a reputation beyond reputejhersh has a reputation beyond reputejhersh has a reputation beyond reputejhersh has a reputation beyond reputejhersh has a reputation beyond reputejhersh has a reputation beyond repute
Re: Java PWM getPosition() integer division bug?

Quote:
Originally Posted by FRC4ME View Post
After much troubleshooting trying to figure out why Servo.get() was returning 0.0 for any servo position other than 1.0, I noticed the following code in edu.wpi.first.wpilibj.PWM:

Code:
public double getPosition() {
    int value = getRaw();
    if (value < getMinNegativePwm()) {
        return 0.0;
    } else if (value > getMaxPositivePwm()) {
        return 1.0;
    } else {
        return (value - getMinNegativePwm()) / getFullRangeScaleFactor();
    }
}
Notice the final return statement. value, getMinNegativePwm(), and getFullRangeScaleFactor() are all of type int. Would this not cause the integer division to truncate to 0 for any result less than 1? I checked the C++ version of the same function, and sure enough, the numerator and denominator of the fraction are cast to float before the division.
Please post a bug report at: http://firstforge.wpi.edu/sf/tracker...ilib_java_bugs

Thanks,
-Joe
Reply With Quote