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I am writing a G-code interpreter and have run into a problem. When the X and Y axis get to their desired position (Right now I just have it return the axis and a .01 unit movement over serial) they just move +0.01 and -0.01 back and forth.

How can I get it to stop it when it reaches the desired position?

Code:
#include <WString.h>                // include the String library
String inString = String(50);       // allocate a new String for the incoming group of chars.
String units = String(2);       // allocate a new String for the units setting. Inches or Milimeters.
String xstr = String(10);       // string for the X caricters to be dumped before thy become and double or float.
String ystr = String(10);       // string for the Y caricters to be dumped before thy become and double or float.
String zstr = String(10);       // string for the Z caricters to be dumped before thy become and double or float.
double xCurrent = 0;
double yCurrent = 0;
double zCurrent = 0;

double xDouble;
double yDouble;
double zDouble;

double xDiference;
double yDiference;
double Diference;

void setup() {
  Serial.begin(9600);               // open the serial port
  Serial.println("start");            // Say hello
}
void loop () {
  if(Serial.available() > 0) {      //add chars if they are avalible
  
    char inChar = Serial.read();    // read the incoming data as a char
    
      if (inChar == 'l'){           // If it is the end of the string decode the string and do the actions.
        char firstChar = inString.charAt(0);
        //start parsing string
        if (firstChar == 'G'){ //Is it a G-code
        GCodeParse();
        }
        else if (firstChar == 'M'){//Is it an M-code
        MCodeParse();
        }
        else{//If it is nether a G or M code send to the computer to continue.
         Serial.println("continue");
        }
        //stop parsing and erase string
        inString = 0;
      }
    else{
        inString.append(inChar); // if you're not at the end of the string, append the incoming character
    }

  }
}

void MCodeParse(){
if (inString.equals("M101")){
         Serial.println("Extruder on");
         //add code for turning on extruder  ---------------------------------------------------<<<
         Serial.println("continue"); // Tell the computer to go on.
}
else if (inString.equals("M103")){
         Serial.println("Extruder off");
         //add code for extruder off  ---------------------------------------------------<<<
         Serial.println("continue"); // Tell the computer to go on.
}
else if (inString.equals("M106")){
         Serial.println("Fan on");
         //add code for fan on  ---------------------------------------------------<<<
         Serial.println("continue"); // Tell the computer to go on.
}
else if (inString.equals("M107")){
         Serial.println("Fan off");
         //add code for fan of  ---------------------------------------------------<<<
         Serial.println("continue"); // Tell the computer to go on.
}
// ----------- do we need extruder P,I,and D gain? Do we need set temp or extrude speed -------------
else{
         Serial.println("continue"); // If unknow code tell the computer to go on.
}
}


void GCodeParse(){
  
if (inString.startsWith("G0 ") || inString.startsWith("G1 ")){ // Is the code for positioing?
         //Code for finding X Y and Z cordenents
         int xcharloc = inString.indexOf('X'); //find where the X code starts
         int ycharloc = inString.indexOf('Y'); //find where the Y code starts
         int zcharloc = inString.indexOf('Z'); //find where the Z code starts
        
         xcharloc = xcharloc + 1;// Code for finding what X is in the code
         ycharloc = ycharloc - 1;
         xstr = inString.substring(xcharloc, ycharloc);
         ycharloc = ycharloc + 1;
        
         ycharloc = ycharloc + 1; // Code for finding what Y is in the code
         zcharloc = zcharloc - 1;
         ystr = inString.substring(ycharloc, zcharloc);
         zcharloc = zcharloc + 1;

         int zlast = inString.length(); // Code for finding what z is in the code, This is some more complex code
         if(inString.contains("F")){
         int fcharloc = inString.indexOf('F'); //find where the F code starts
         zcharloc = zcharloc + 1;
         fcharloc = fcharloc - 1;
         zstr = inString.substring(zcharloc, fcharloc);
         zcharloc = zcharloc - 1;
         fcharloc = fcharloc + 1;  
         }else{
         zcharloc = zcharloc + 1;
         zstr = inString.substring(zcharloc, zlast);
         Serial.print(zstr);
         Serial.println(" <Z value");
         zcharloc = zcharloc - 1;
         }
        
         xDouble = atof(xstr); //convert string with x cordanents to double format
         yDouble = atof(ystr); //convert string with y cordanents to double format
         zDouble = atof(zstr); //convert string with z cordanents to double format
        
         Serial.print("X as a double : ");
         Serial.println(xDouble);
         Serial.print("Y as a double : ");
         Serial.println(yDouble);
         Serial.print("Z as a double : ");
         Serial.println(zDouble);
    
        if(zCurrent == zDouble){ // If a new Z position is not requested do nothing.
        }else{//if it is requested move the axie
        
           while(zCurrent < zDouble){  //Do we move up?
             //Move tward zDouble by 0.01 units
             Serial.print("z+");
             zCurrent = zCurrent + 0.01; //write in current location
           }
           while(zCurrent > zDouble){ //Or do we move down?
             //Move tward zDouble by 0.01 units
             Serial.print("z-");
             zCurrent = zCurrent - 0.01; //write in current location
           }
          
        }
        
        move();
        
        Serial.println("continue"); // Tell the computer to go on when you are done.
}

else if (inString.startsWith("G20 ")){
         units = "in";
         Serial.println("continue"); // Tell the computer to go on.
}
else if (inString.startsWith("G21 ")){
         units = "mm";
         Serial.println("continue"); // Tell the computer to go on.
}
// ---------------------------???Do we need "G28, G30, G90, G91, G92"??? Arcs? Dwells?--------------------------
else{
         Serial.println("continue"); // If unknow code tell the computer to go on.
}

}


void xBig(){
}
void yBig(){
}
void xSmall(){
  if(xDouble == xCurrent){
  //do nothing!!!
  }else{
    if(xCurrent < xDouble){  //Do we move up?
      Serial.print("x+"); //Move tward zDouble by 0.01 units
      xCurrent = xCurrent + 0.01; //write in current location
    }else{
      Serial.print("x-"); //Move tward zDouble by 0.01 units
     xCurrent = xCurrent - 0.01; //write in current location
    }
  }
}
void ySmall(){
  if(yDouble == yCurrent){
  //do nothing!!!
  }else{
   if(yCurrent < yDouble){  //Do we move up?
      Serial.print("y+"); //Move tward zDouble by 0.01 units
      yCurrent = yCurrent + 0.01; //write in current location
    }else{
      Serial.print("y-"); //Move tward zDouble by 0.01 units
     yCurrent = yCurrent - 0.01; //write in current location
    }
  }
}


void move(){
 while(xDouble != xCurrent||yDouble != yCurrent);{
  // Find the difference
if(yDiference > 0 && xDiference > 0){
if(xDouble > xCurrent){
  xDiference = xDouble - xCurrent;
}else{
 xDiference = xCurrent - xDouble;
}
if(yDouble > yCurrent){
  yDiference = yDouble - yCurrent;
}else{
 yDiference = yCurrent - yDouble;
}
if(xDiference > yDiference){
 Diference = xDiference/yDiference;
}else{
 Diference = yDiference/xDiference;
}                     // STOP finding the difference
}else{
}

 Serial.print(Diference); // Tell the godfather what the difference is.
 Serial.print("X: ");
 Serial.print(xCurrent);
 Serial.print("Y: ");
 Serial.println(yCurrent);

 if(xDiference > yDiference){
   xSmall();
   ySmall();
 }else{
   xSmall();
   ySmall();
 }
 
 
}


}


The Part I am having trouble with is the void xSmall(), ySmall(), and move().
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While I can't address the problem you're having, I can say that comparing two doubles for equality...

  if(yDouble == yCurrent){

...is not a good idea.  This is a good description of the problem and solutions...

http://www.cygnus-software.com/papers/comparingfloats/comparingfloats.htm

Good luck,
Brian
« Last Edit: April 22, 2009, 07:45:07 pm by bcook » Logged

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Yea that looks like the issue. I tried the epsilon method but now the two variables being compared are thought to be equal when they are not. :-?
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that means your epsilon value is too large.
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Movement is in 0.01 unit increments so an absolute comparison is probably the better choice...

  if ( abs( yDouble - yCurrent ) <= 0.005 )

I have no idea if "abs" is available.  If not you'll have to create one.

Good luck,
Brian
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abs is available but is still doesn't work.
« Last Edit: April 22, 2009, 08:03:31 pm by jeffonfire » Logged

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In your move():

Code:
while(xDouble != xCurrent||yDouble != yCurrent)[glow];[/glow]{
...
}
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YEAY, i messed with it for about 10 min and now it is working!!!!

Thanks to everyone who posted!!! smiley-wink
« Last Edit: April 23, 2009, 03:59:41 pm by jeffonfire » Logged

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