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Reversing return value of nMotorEncoder

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Reversing return value of nMotorEncoder

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sifu

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Joined: Fri Jul 26, 2013 4:29 pm
Posts: 5

Reversing return value of nMotorEncoder

Hi everyone.

I'm trying to do the Ring it Up challenge, and I was curious as to if there was a way to reverse the value that nMotorEncoder returned. I'm having a problem where the reversed motors (on the left side of the scissor bot) will run "forwards" while the encoder still reads as if it is going backwards.

Thanks

Fri Aug 09, 2013 10:02 pm

rcahoon

Site Admin

Joined: Tue Oct 09, 2012 10:34 am
Posts: 192

Re: Reversing return value of nMotorEncoder

Hi sifu,
Just put a "minus" sign in front of it. For example:


	Code: -nMotorEncoder[leftMotor]

Cheers,
--Ryan

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Ryan Cahoon
CMU Robotics Academy
RVW Software Developer

Robot Potato Head; Virtual NXT

Fri Aug 09, 2013 10:05 pm

sifu

Rookie

Joined: Fri Jul 26, 2013 4:29 pm
Posts: 5

Re: Reversing return value of nMotorEncoder

Thanks for the response, but there is anyway to permanently reverse the value, similar to reversing a motor in the setup. Otherwise it makes the code a bit harder to write.

Sat Aug 10, 2013 3:04 pm

mightor

Site Admin

Joined: Wed Mar 05, 2008 8:14 am
Posts: 3654
Location: Rotterdam, The Netherlands

Re: Reversing return value of nMotorEncoder

Mount the motor in reverse

= Xander

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Sat Aug 10, 2013 3:34 pm

rcahoon

Site Admin

Joined: Tue Oct 09, 2012 10:34 am
Posts: 192

Re: Reversing return value of nMotorEncoder


	sifu wrote: permanently reverse the value

I don't know of any way intrinsic to the ROBOTC, but you could make your own wrapper on nMotorEncoder that accomplishes this. You could make a nicer, general form if ROBOTC supported preprocessor token pasting, but here's an idea that will work:


	Code: #define getLeftMotorEncoder() (-nMotorEncoder[leftMotor]) #define setLeftMotorEncoder(val) (nMotorEncoder[leftMotor] = -(val))

Then you can use them like:


	Code: task main() { //Clear Encoders setLeftMotorEncoder(0); while(getLeftMotorEncoder() < 1800) // While less than 5 rotations on the leftEncoder... { //...Move Forward motor[rightMotor] = 63; motor[leftMotor] = 63; } }

You can define similar sets of macros for each of your motors.

Cheers,
--Ryan

_________________
Ryan Cahoon
CMU Robotics Academy
RVW Software Developer

Robot Potato Head; Virtual NXT

Mon Aug 12, 2013 2:18 pm

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