Encoders Programming
 

Hello my name is David and I'm tge lead programmer for FRC Team 4780 and I was wondering if anyone could tell me how to programm the 2013 KOP quadrature encoders.

Re: Encoders Programming
 

Everything covered in your other thread is directly applicable.
http://www.chiefdelphi.com/forums/sh...d.php?t=119184

Re: Encoders Programming
 

Also you should check out the Javadoc page for the Encoder class. If you weren't aware, you can find the Javadoc for WPILib at 'C:\Users\username\sunspotfrcsdk\doc\javadoc\index.html' on any computer set up for Java development. Alternatively, here's a link to a copy on the web. Particularly note the Encoder#get() and Encoder#getRate() methods, which give you the position and the rotation rate of the encoder respectively.

Re: Encoders Programming
 

It depends on where the encoder is located (e.g. drive wheel gearbox, frisbee shooter wheel, etc) and what you are trying to accomplish with the signal (e.g. track distance in autonomous, control wheel speed, etc).

Re: Encoders Programming
 

Im using them on the Toughbox Mini (am-0654) to track distance in autonomous.

Re: Encoders Programming
 

Hey so I've been trying to get the encoders programmed on the Toughbox Mini (am-0654) but have been running into a problem. Everytime I get a distance from the encoders it goes from 0.3 to 0.0, any suggestions?

public void takeJoystickInputs(Joystick right) {
SmartDashboard.putData("Left Encoder Distance", leftEncoder);
SmartDashboard.putData("Right Encoder Distance", rightEncoder);
if ((36+((leftEncoder.getDistance()+ -rightEncoder.getDistance())/2)) > 0) {robotDrive2.arcadeDrive(right.getY(), -right.getX());}
else robotDrive2.drive(0, 0);
//robotDrive2.arcadeDrive(right.getY(), -right.getX());
}

Re: Encoders Programming
 

Check the wiring of the encoders/PWMs. I know that my team has had similar issues when the PWM cables were plugged in backwards.

Also note that using the Encoder#getDistance() method requires you to have set a distance with Encoder#setDistancePerPulse(double). If you didn't set this value, you will be getting inaccurate readings. Assuming the encoders are 360 pulses/revolution (which the kit E4Ps should be), the number you need is just the distance your robot travels in one encoder revolution divided by 360.

Re: Encoders Programming
 

Hey so I've been trying to get the encoders programmed on the Toughbox Mini (am-0654) but have been running into a problem. Everytime I get a distance from the encoders it goes from 0.3 to 0.0, any suggestions?

public void takeJoystickInputs(Joystick right) {
SmartDashboard.putData("Left Encoder Distance", leftEncoder);
SmartDashboard.putData("Right Encoder Distance", rightEncoder);
if ((36+((leftEncoder.getDistance()+ -rightEncoder.getDistance())/2)) > 0) {robotDrive2.arcadeDrive(right.getY(), -right.getX());}
else robotDrive2.drive(0, 0);
//robotDrive2.arcadeDrive(right.getY(), -right.getX());
}

Re: Encoders Programming
 

Can you draw and post a sketch of how you have it wired? Or take a couple of pictures (preferably with your camera set to "macro").

Re: Encoders Programming
 

Can you show your constructor call for the LeftEncoder and RightEncoder object?

An encoder that toggles between 0 and another value is because the software is only reading a single channel, instead of both channels. This could be because of a wiring problem or a software initialization problem (as in you hooked channel A and B to DIO 1 and 2, but told the software to use DIO 2 and 3.

Switching A & B makes the encoder count in reverse, but still counts.

Re: Encoders Programming
 

public void takeEncoderInputs() {
leftEncoder.start();
rightEncoder.start();
leftEncoder.setDistancePerPulse(18.84/1620);
rightEncoder.setDistancePerPulse(18.84/1620);
leftEncoder.getDistance();
rightEncoder.getDistance();
SmartDashboard.putData("Left Encoder Distance", leftEncoder);
SmartDashboard.putData("Right Encoder Distance", rightEncoder);

Re: Encoders Programming
 

None of those are the constructor for leftEncoder or rightEncoder. Look for the part where you use new.

Re: Encoders Programming
 

Looking at your other thread, I see you are using the AS5145B Magnetic Encoders, not the US Digital E4Ps. According to this page, these encoders output 1024 pulses per revolution, unlike the E4Ps which are only 360 pulses/revolution.

Have you looked at this page yet? It explains how quadrature encoders work, and gives some examples of how to use the WPILib Encoder class.

The constructor call is where you create the Encoder object, usually as an instance variable of your robot class. For example, to create an Encoder with the A channel in DIO 1, the B channel in DIO 2, counting the normal direction and 4X decoding, you would use this:
Here's a simple example of using encoders to drive a robot in autonomous: https://gist.github.com/DomenicP/7252269

Re: Encoders Programming
 

My bad, here you go

driveTrainLeftEncoder = new Encoder(1, 1, 1, 2, false, EncodingType.k4X);
driveTrainRightEncoder = new Encoder(1, 3, 1, 4, false, EncodingType.k4X);

Re: Encoders Programming
 

I've gone through my wiring and code several times and still can't figure out why the encoders' values keep resetting. It feel like I'm so close but so far away from because of this.

Re: Encoders Programming
 

You haven't yet posted how you wired it or taken any pictures, per Ether's request.

Re: Encoders Programming
 

So I have the two bare red wires to one of the grounds and the other to csn and soldered to the black which is connected to the other ground. I also have the blues connected to channel a and the yellow to channel b and red to 5v. the red and blue are in dio 1 and yellow and black are connected to dio 2.

Re: Encoders Programming
 

I found another thread related to the magnetic encoders. You might want to look through it if you haven't already: http://www.chiefdelphi.com/forums/sh...d.php?t=111202

Also, here's the non FIRST-specific data sheet for the sensor: http://www.ams.com/eng/content/downl...heet_v1-15.pdf

Unfortunately I can't see the wiring very well from the pictures provided, so I won't be of much help there. It seems the sensor has two modes of output: absolute position, and quadrature output. For you usage, you need to make sure you wire it for quadrature output. Here's the wiring:

Source. Attached is a sketch of what (I believe) the wiring should look like.

Re: Encoders Programming
 

yep thats exactly how it is wired

Re: Encoders Programming
 

^ditto that.

What part number magnet are you using?

Re: Encoders Programming
 

Here are some other things to consider:

Are both encoders giving you identical output? It might be easier to look at the output using System.out.println() rather than SmartDashboard. The output goes to the console in NetBeans, and from my experience is more useful for debugging.

Are you calling Encoder#start() more than once for the encoders? You should only need to call it once at the beginning of the program, unless you stop counting with Encoder#stop(). I don't know if this would cause the encoder count to reset though.

Have you checked for hardware defects? Ensure that there is nothing wrong with your digital sidecar and cables. As Joe Ross mentioned earlier, the problem you described is often because only one channel of the encoder is being read.

Does your team have any other encoders, such as the US Digital E4P? You could try swapping one out temporarily to see if it behaves any differently. This would help identify it as a hardware or a software issue.

Re: Encoders Programming
 

You may want to consider setting up a couple of DigitalInputs in code and read/println the two encoder inputs while slowly spinning the shaft by hand: you should be able to see the inputs toggle. That would tell you if it's wiring (or wrong/bad input) or problems setting up the Counter class....

Re: Encoders Programming
 

Hi David. You haven't posted in 10 days. Did you ever get your problem solved? Please tell us about it.

Re: Encoders Programming
 

I still haven't figured out the encoder resetting problem sadly. I had about 2 months of just thinking about it while I worked on the Safety Animation but the program I came up with inevitably failed. I might just end up going through and yanking everything because the only thing I can think of is it's a wiring problem.