How to use Pixy over I2C?

blakehelton · April 6, 2018, 10:20pm

Hello! I need to write code to use a Pixy over the I2C interface to get, for now, the X, Y, and Size of an object. We’ve been using just Analog-Digital for awhile, but need to track multiple objects now. I’ve looked at some code from other teams, but can’t entirely seem to figure out how I should be doing this. Any help would be greatly appreciated!

otherguy · April 8, 2018, 1:50pm

I’ve never used the pixy before, but there seems to be a number of posts and github programming examples available.

FRC2876 - 2017 code

github.com

BHSRobotix/Steamworks2017/blob/master/src/org/usfirst/frc2876/Steamworks2017/subsystems/PixyI2C.java

package org.usfirst.frc2876.Steamworks2017.subsystems;

import edu.wpi.first.wpilibj.I2C;
import edu.wpi.first.wpilibj.I2C.Port;
import edu.wpi.first.wpilibj.smartdashboard.SmartDashboard;

public class PixyI2C {
	String name;
	PixyPacket values;
	I2C pixy;
	Port port = Port.kOnboard;
	PixyPacket[] packets;
	PixyException pExc;
	String print;

	public PixyI2C(String id, I2C argPixy, PixyPacket[] argPixyPacket, PixyException argPixyException,
			PixyPacket argValues) {
		pixy = argPixy;
		packets = argPixyPacket;
		pExc = argPixyException;

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github.com

BHSRobotix/Steamworks2017/blob/master/src/org/usfirst/frc2876/Steamworks2017/subsystems/Vision.java#L55


      
          	public void testGearPixy() {
          		for (int i = 0; i < packet1.length; i++)
          			packet1[i] = null;
          		SmartDashboard.putString("gearPixy hello", "working");
          		for (int i = 1; i < 8; i++) {
          			try {
          				packet1[i - 1] = gearPixy.readPacket(i);
          			} catch (PixyException e) {
          				SmartDashboard.putString("gearPixy Error: " + i, "exception");
          			}
          			if (packet1[i - 1] == null) {
          				SmartDashboard.putString("gearPixy Error: " + i, "True");
          				continue;
          			}
          			SmartDashboard.putNumber("gearPixy X Value: " + i, packet1[i - 1].X);
          			SmartDashboard.putNumber("gearPixy Y Value: " + i, packet1[i - 1].Y);
          			SmartDashboard.putNumber("gearPixy Width Value: " + i, packet1[i - 1].Width);
          			SmartDashboard.putNumber("gearPixy Height Value: " + i, packet1[i - 1].Height);
          			SmartDashboard.putString("gearPixy Error: " + i, "False");
          		}
          	}

FRC2363 - 2017 Code

github.com

TripleHelixProgramming/Steamworks/blob/master/Steamworks/src/org/usfirst/frc/team2363/util/Pixy.java

package org.usfirst.frc.team2363.util;

import java.util.Optional;

import org.usfirst.frc.team2363.robot.RobotMap;

import edu.wpi.first.wpilibj.DriverStation;
import edu.wpi.first.wpilibj.I2C;
import edu.wpi.first.wpilibj.smartdashboard.SmartDashboard;

/**
 *
 */
public class Pixy {

	public static I2C pixyi2c;
	public static PixyPacket previousPkt = new PixyPacket();
	public int targetX;
	
	public Pixy() {

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github.com

TripleHelixProgramming/Steamworks/blob/master/Steamworks/src/org/usfirst/frc/team2363/robot/commands/shooter/PixyCheck.java

package org.usfirst.frc.team2363.robot.commands.shooter;

import org.usfirst.frc.team2363.robot.Robot;
import static org.usfirst.frc.team2363.robot.Robot.lightRing;
import edu.wpi.first.wpilibj.DriverStation;
import edu.wpi.first.wpilibj.command.Command;
import edu.wpi.first.wpilibj.smartdashboard.SmartDashboard;

/**
 *  PixyCheck command is used to check that we are receiving data from the Pixy Cam
 */
public class PixyCheck extends Command {

    public PixyCheck() {
        // Use requires() here to declare subsystem dependencies
        // eg. requires(chassis);
    	requires(lightRing);
    }

    // Called just before this Command runs the first time

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github.com

TripleHelixProgramming/Steamworks/blob/db88a6b0ed837c1043840c69c593ff1db1af7bc5/Steamworks/src/org/usfirst/frc/team2363/robot/commands/drivetrain/TurnToX.java#L79


      
              }
          
              // Called when another command which requires one or more of the same
              // subsystems is scheduled to run
              protected void interrupted() {
              }
          
          	@Override
          	protected double returnPIDInput() {
          		
          		targetX = Robot.pixy.getTargetX();
          		
          		if (targetX != -1) {
          			previousX = targetX;
          			noTargetCount = 0;
          			SmartDashboard.putString("Target X: ", "" + targetX);
          			DriverStation.reportError("Target X :" + targetX, false);
          			return targetX;
          		} else {
          			noTargetCount++;
          			SmartDashboard.putString("Target X: ", "Using previous X = " + previousX);

CD Post w/ useful links:

4ShocK · April 9, 2018, 9:14pm

You will need to make a cable. Our team got these from Amazon.
Cut the end of one of the connectors and follow the chart here. Just make sure that the end you are starting with has the red stripe (or whatever color you plan on using) as 1. Otherwise prepare to be very confused.
Follow the lines and see which ones need to go to the roborio’s i2c. You can leave out the 3v port on the roborio, we chose to power the pixy from the VRM. You can find a pinout for that if you arent doing so already.
Once you are done with that, just put it in a 4 pin housing and it should work.

I also have code on my github.
If you need any help, let me know. I write things in a confusing manner

system · January 5, 2020, 10:16am