RobotControl::motorsWritePct bug

[bkmartinjr]

Version 1.0.5 of the IDE. RobotControl::motorsWritePct() has an arithmetic error when computing the left/right motor speed.

Both the left/right values need to be divided by 100.

Old code:

    int16_t speedLeft=255*speedLeftPct;
    int16_t speedRight=255*speedRightPct;

I believe it should read:

    int16_t speedLeft=255*speedLeftPct / 100;
    int16_t speedRight=255*speedRightPct / 100;

[lestofante]

100.0, or you are teuncating the decimal part. Also some parentesis should
help readibility
Il giorno 21/giu/2013 22:07, "bkmartinjr" [email protected] ha
scritto:

Version 1.0.5 of the IDE. RobotControl::motorsWritePct() has an arithmetic
error when computing the left/right motor speed.

Both the left/right values need to be divided by 100.

Old code:

int16_t speedLeft=255*speedLeftPct;
int16_t speedRight=255*speedRightPct;

I believe it should read:

int16_t speedLeft=255*speedLeftPct / 100;
int16_t speedRight=255*speedRightPct / 100;

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/1478
.

[bkmartinjr]

The function input parameters (speedLeftPct and speedRightPct) are both integer type, with presumed value [0-100]. I don't believe the original implementer wanted floating point arithmetic, for efficiency's sake. So there should be no decimal in the constant (i.e., the constant should be 100, not 100. ) and my original patch is correct.

I leave it up to the integrator to decide if quotes really help, given the standard C precedence rules. I wouldn't re-order the expression due to loss of precision.

Caveat: this seems to be an undocumented function (not listed in the arduino.cc reference page for Robot library). So my assumptions about the correct function behavior may be incorrect.

[cmaglie]

Fixed in 1.5.6 with X-Y@53adddc