Thread: Pixy I2C
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Unread 02-13-2015, 04:57 PM
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FRC #1559 (DevilTech)
Team Role: Programmer
 
Join Date: Apr 2013
Rookie Year: 2013
Location: New York
Posts: 19
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Re: Pixy I2C

Hi there. Here is what out team is using to pry information out of the pixy. I hope this helps! I'm not sure why the code block is anti-tabbing...

(the code gpetilli mentioned)

Code:
import edu.wpi.first.wpilibj.SerialPort;
import edu.wpi.first.wpilibj.SerialPort.Port;
//Warning: if the pixy is plugged in through mini usb, this code WILL NOT WORK b/c the pixy is smart and detects where it should send data
public class Pixy {
SerialPort pixy;
Port port = Port.kMXP;
PixyPacket[] packets;
PixyException pExc;
String print;
public Pixy() {
pixy = new SerialPort(19200, port);
pixy.setReadBufferSize(14);
packets = new PixyPacket[7];
pExc = new PixyException(print);
}
//This method parses raw data from the pixy into readable integers
public int cvt(byte upper, byte lower) {
return (((int)upper & 0xff) << 8) | ((int)lower & 0xff);
}
public void pixyReset(){
pixy.reset();
}
//This method gathers data, then parses that data, and assigns the ints to global variables
public PixyPacket readPacket(int Signature) throws PixyException {
int Checksum;
int Sig;
byte[] rawData = new byte[32];
try{
rawData = pixy.read(32);
} catch (RuntimeException e){
}
if(rawData.length < 32){
System.out.println("byte array length is broken");
return null;
}
for (int i = 0; i <= 16; i++) {
int syncWord = cvt(rawData[i+1], rawData[i+0]); //Parse first 2 bytes
if (syncWord == 0xaa55) { //Check is first 2 bytes equal a "sync word", which indicates the start of a packet of valid data
syncWord = cvt(rawData[i+3], rawData[i+2]); //Parse the next 2 bytes
if (syncWord != 0xaa55){ //Shifts everything in the case that one syncword is sent
i -= 2;
}
//This next block parses the rest of the data
Checksum = cvt(rawData[i+5], rawData[i+4]);
Sig = cvt(rawData[i+7], rawData[i+6]);
if(Sig <= 0 || Sig > packets.length){
break;
}
packets[Sig - 1] = new PixyPacket();
packets[Sig - 1].X = cvt(rawData[i+9], rawData[i+8]);
packets[Sig - 1].Y = cvt(rawData[i+11], rawData[i+10]);
packets[Sig - 1].Width = cvt(rawData[i+13], rawData[i+12]);
packets[Sig - 1].Height = cvt(rawData[i+15], rawData[i+14]);
//Checks whether the data is valid using the checksum *This if block should never be entered*
if (Checksum != Sig + packets[Sig - 1].X + packets[Sig - 1].Y + packets[Sig - 1].Width + packets[Sig - 1].Height) {
packets[Sig - 1] = null;
throw pExc;
}
break;
}
}
//Assigns our packet to a temp packet, then deletes data so that we dont return old data
PixyPacket pkt = packets[Signature - 1];
packets[Signature - 1] = null;
return pkt;
}
}
Code:
public class PixyException extends Exception {
public PixyException(String message){
super(message);
}
}
Code:
public class PixyPacket {
public int X;
public int Y;
public int Width;
public int Height;
}
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Last edited by 2B || !2B : 02-13-2015 at 05:01 PM. Reason: I forgot to mention something.
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