How to Program a Servo

[ExarKun666]

Okay I am not sure how to program the servo, I have a servo plugged into the digital sidecar on PWM #3, and I am not sure how to program it moving so this is the code that we have, so could you tell us our problem?

#include "WPILib.h"
#include "xmath.h"

class RobotDemo : public SimpleRobot
{
   RobotDrive myRobot;
   Joystick leftstick;
   Joystick rightstick;
   Servo servo;
public:
   RobotDemo(void):
      myRobot(1, 2, 3),
      leftstick(1),
      rightstick(2),
      servo(3)
   {
       GetWatchdog().SetExpiration(100);
   }
   void Autonomous(void)
   {
       GetWatchdog().SetEnabled(false);
       //CODE
    }
void OperationControl(void)
{
   Servo(3);
   GetWatchdog().SetEnabled(true);
   while(IsOperatorControl())
   {
      servo.Set(170.0);
      GetWatchdog().Feed();
   }
}
};

So any suggestions?

[pheadxdll]

I think your major problem is that you haven't read any of the documentation on C++ coding: http://first.wpi.edu/Images/CMS/First/FRC1718Docs.zip There's a nice packet of information there. Here's how to fix your program:

void OperationControl(void)
{
   GetWatchdog().SetEnabled(true);
   while(IsOperatorControl())
   {
      servo.Set(1.0);
      GetWatchdog().Feed();
   }
}

The Set method takes a value from 0.0 to 1.0 (full left to full right)

Also, make sure you have a jumper set on the sidecar next to the pwm output for the servo.

[byteit101]

The Set method takes a value from 0.0 to 1.0 (full left to full right)

Not on a servo (last i checked it is 0-170) though I don't know about the team update 3

[3DWolf]

Originally Posted by byteit101

Not on a servo (last i checked it is 0-170) though I don't know about the team update 3

You're getting your functions confused.
servo.Set() accepts a range from -1 to 1 for min to max values of the servo - this is here so you can just directly accept another float value from something else (like a joystick) and just set it directly.
servo.SetAngle() accepts an angle that you wish to set your servo at. Try using this with your 170 angle and see if that works.

[byteit101]

Originally Posted by 3DWolf

You're getting your functions confused.
servo.Set() accepts a range from -1 to 1 for min to max values of the servo - this is here so you can just directly accept another float value from something else (like a joystick) and just set it directly.
servo.SetAngle() accepts an angle that you wish to set your servo at. Try using this with your 170 angle and see if that works.

it is 0 to 1 not -1 to 1

Originally Posted by WPILib

/**
* Set the servo position.
*
* Servo values range from 0.0 to 1.0 corresponding to the range of full left to full right.
*
* @param value Position from 0.0 to 1.0.
*/
void Servo::Set(float value)

[3DWolf]

Originally Posted by byteit101

it is 0 to 1 not -1 to 1

Oh, right. Most of the other functions are -1 to 1, didn't look at the docs.
If you need to scale (-1, 1) to (0, 1) you can use
prevVal = joystick(1)->Get(); //-1 to 1 value
ScaledVal = (prevVal + 1)/2; //Scaled to 0 to 1