Wrote a basic program to do linear interpolation from coordinates received over the serial interface. Now I need to find an easy way to send coords from a graphics program.
Trying to decide what I need to write so that I can communicate with some open source machine control software. The Arduino can't do a lot on it's own, but it needs to interpret commands.
Looks like some machines support HPGL code. That is reasonably simple to implement but will require writing several functions. It is a short term solution
This guy made an HPGL GUI
http://www.linuxcnc.org/component/option,com_kunena/Itemid,20/func,view/catid,31/id,1870/lang,english/
www.securetech-ns.ca/camm-linux.html
Many graphics programs can output HPGL. This will be for mostly 2D projects, like PCB cutting.
this guy wrote an HPGL interpretor, that i looked at for ideas, but didn't end up trying to use it
http://sensi.org/~svo/motori/
This page has a simple HGL file that I used for test
http://www.winline.com/evalpen_center.html
http://www.winline.com/images/plotfiles/GL-C-O.plt
Wrote this very basic HPGL control layer to interface from basic HPGL commands to control the adafruit motor shield:
The bug i have right now is that if i send the very long coord lists in this file, i fill the Arduino serial buffer and it hoses the data, since the Arduino has to move the motors, reading the data as it comes doesn't quite work. Meanwhile this is what i have so far, that works will with manually entered commands.
// Stepper Motor Control Program
// For an XYZ stepper motor controller
// Receives serial commands from PC, controls 3 motor CNC machine
// Interprets basic HPGL style instructions
// Tom Wilson 2011
#define INCH 4000 //steps per inch of the machine = threads per inch * steps per rotation
#define RPM 30 //speed of the motors
#define SER_HEADER 'G' // Header tag for serial message
// Adafruit Motor shield library
// modified by tomw to drive 2 shields at once
// This requires a modified library
//with the second having MOTORLATCH on pin 13, renamed MOTORLATCHA
//and all functions renamed to A versions
#include <AFMotor.h>
#include <AFMotorA.h>
//Set up the steps per revolution and location of motors
AF_Stepper motorX(200, 1);
AF_Stepper motorY(200, 2);
AF_StepperA motorZ(200, 2);
// Set up the basic machine position variable
signed long int Xpos = 0;
signed long int Ypos = 0;
signed long int Zpos = 0;
// Set up the destination machine position variable
signed long int newXpos = 0;
signed long int newYpos = 0;
signed long int newZpos = 0;
// Set up global place to keep serial values
signed long int newSerialData;
bool XorY = false;
void setup() {
Serial.begin(9600); // set up Serial library at 9600 bps
Serial.println("Stepper Controller Online");
//set the default speed of the motors
motorX.setSpeed(RPM); ;
motorY.setSpeed(RPM); ;
motorZ.setSpeed(RPM); ;
delay(1000); // wait for the supply to come up
//step motors one step and back to power the coils
motorX.step(1, FORWARD, SINGLE);
motorY.step(1, FORWARD, SINGLE);
motorZ.step(1, FORWARD, SINGLE);
motorX.step(1, BACKWARD, SINGLE);
motorY.step(1, BACKWARD, SINGLE);
motorZ.step(1, BACKWARD, SINGLE);
// Home position
Xpos = 0;
Ypos = 0;
Zpos = 0;
newXpos = 0;
newYpos = 0;
newZpos = 0;
Serial.print("Current:");
Serial.print("\tX:");
Serial.print(Xpos);
Serial.print("\tY:");
Serial.print(Ypos);
Serial.print("\tZ:");
Serial.println(Zpos);
Serial.println("Ready for Commands");
}
void loop() {
while(Serial.available() ) {
// Loop simply accepts commands from serial and executes them
readHPGLcommand(); //read the command
}
}
void readHPGLcommand() {
// reads serial port for two letter HPGL command and optional coords that follow
char c;
bool coord_avail;
//make sure there is enough data there for form a command, at least "IN;"
if(Serial.available()>=3){
c = Serial.read();
// Interpret HPGL command, ingnore unsupported commands and whitespace
//http://paulbourke.net/dataformats/hpgl/ has definitions
switch( c ) {
case 'P' :
switch( Serial.read() ) {
case 'U' : // PU Pen Up
Serial.println("Pen Up \t/\\ /\\ /\\ /\\"); //lift pen and optionally move to new coords
zMove(50);
// expect either nothing or pairs of coords to follow
XorY = true;
coord_avail = true;
while( coord_avail ) {
coord_avail = readSerialNumber();
// hack to alternate reading values as X or Y
if ( XorY) {
newXpos = newSerialData;
XorY = false;
} else {
newYpos = newSerialData;
XorY = true;
Serial.print(newXpos); Serial.print(":"); Serial.print(newYpos); Serial.print("\t>>");
linearInterpolationMove( newXpos, newYpos);
}
}
break;
case 'D' : // PD Pen Down
Serial.println("Pen Down\t\\/ \\/ \\/ \\/"); //drop pen and optionally move to new coords
zMove(0);
coord_avail = false;
// expect either nothing or pairs of coords to follow
XorY = true;
coord_avail = true; //need to make sure the loop goes at least once
while( coord_avail ) {
coord_avail = readSerialNumber();
// hack to alternate reading values as X or Y
if ( XorY) {
newXpos = newSerialData;
XorY = false;
} else {
newYpos = newSerialData;
XorY = true;
// only valid coord if two values were found
Serial.print(newXpos); Serial.print(":"); Serial.print(newYpos); Serial.print("\t>>");
linearInterpolationMove( newXpos, newYpos);
}
}
break;
case 'G' : // PG Page Feed
Serial.println("Page Feed");
while( readSerialNumber() ) {} //keep reading until coords or ';' is found
// Command doesn't do anything yet
break;
case 'T' : // PG Pen Thickness
Serial.println("Pen Thickness");
while( readSerialNumber() ) {} //keep reading until coords or ';' is found
// expects one number to be returned, indicating pen
Serial.print("Pen Thickness Set to:");
Serial.println(newSerialData);
// currently not doing anything with this command
break;
default :
Serial.println("WARNING: Unknown command Px ignored");
while( readSerialNumber() ) {} //keep reading until coords or ';' is found
break;
}
break;
case 'I' :
switch( Serial.read() ) {
case 'N' : // IN Initialize
Serial.println("Initialize");
while( readSerialNumber() ) {} //keep reading until coords or ';' is found
// Home position
Xpos = 0;
Ypos = 0;
Zpos = 0;
break;
default :
Serial.println("WARNING: Unknown command Ix ignored: ");
while( readSerialNumber() ) {} //keep reading until coords or ';' is found
break;
}
break;
case 'S' :
switch( Serial.read() ) {
case 'P' : // SP Select Pen
Serial.println("Select Pen");
while( readSerialNumber() ) {} //keep reading until coords or ';' is found
// expects one number to be returned, indicating pen
Serial.print("Pen set to:");
Serial.println(newSerialData);
// currently not doing anything with this command
break;
default :
Serial.print("WARNING: Unknown command Sx ignored: ");
while( readSerialNumber() ) {} //keep reading until coords or ';' is found
break;
}
break;
default :
//Whitespace or unrecognized letter, ignore it
break;
} //cmd switch
} //if serial
}
bool readSerialNumber() {
//read coords from serial input
//commands end with ';' and lists of coords are separated by ','
//
// Three things can happen and need to differentiate
// 1) no coords at all, just a ; - need to return right away and break the calling while loop
// 2) a coordinate followed by , - need to output the coord and continue
// 3) a coordinate followed by ; - need to output the coord and break the calling while loop
signed long int coord = 0; //temp storage for coords from serial
signed int sign = 1; //temp storage for coord sign from serial
char c;
while ( c != ',' && c != ';' /*&& Serial.available()*/){
c = Serial.read();
if( c == '-' ) sign = -1; // capture the sign
if( c >= '0' && c <= '9'){
coord = (10 * coord) + (c - '0') ; // convert digits to a number
}
}
//put the data in the top level variable
newSerialData = coord * sign;
//detect the end of command ';' after the last coord
if( c == ';') return false;
return true;
}
void zMove (signed long int newZ) {
//calculates steps to move, and moves, to new Z position requested
signed long int distance = 0;
signed long int oldZ = Zpos;
distance = newZ - oldZ;
if ((distance < 8000) && (distance > -8000)) {
if (distance >= 1) motorZ.step(distance, FORWARD, SINGLE);
if (distance <= -1) motorZ.step(-1*distance, BACKWARD, SINGLE);
} else {
//movement requested is large and likely an error
Serial.println("ERROR - Z axis out of range");
}
Zpos = newZ; //update machine current position
}
void linearInterpolationMove ( signed long int newX, signed long int newY) {
float distance = 0;
int stepnum = 0;
signed long int nextX;
signed long int nextY ;
signed long int oldX = Xpos;
signed long int oldY = Ypos;
Serial.print("\t");
Serial.print(Xpos);
Serial.print(":");
Serial.print(Ypos);
Serial.print("\t --");
//find the hypotenuse, the total distance to be traveled
distance = sqrt((newX - oldX)*(newX - oldX) + (newY - oldY)*(newY - oldY) );
//round to integer number of steps that distance. Step by two to minimize 0 size steps.
for (stepnum=0; stepnum <= (distance + 0.5); stepnum++) {
//calculate the nearest integer points along the way
nextX = oldX + stepnum/distance*(newX-oldX);
nextY = oldY + stepnum/distance*(newY-oldY);
//move machine to that new coordinate, if 0 delta, don't move
if ((distance < 7*INCH) && (distance > -7*INCH)) { //trap crazy value
/* removed for test
if ((nextX-Xpos) >= 1) motorX.step((nextX - Xpos)*INCH/1000, FORWARD, SINGLE);
if ((nextX-Xpos) <= -1) motorX.step((Xpos - nextX)*INCH/1000, BACKWARD, SINGLE);
if ((nextY-Ypos) >= 1) motorY.step((nextY - Ypos)*INCH/1000, FORWARD, SINGLE);
if ((nextY-Ypos) <= -1) motorY.step((Ypos - nextY)*INCH/1000, BACKWARD, SINGLE);
*/
//update the machine current position
Xpos = nextX;
Ypos = nextY;
} else {
Serial.println("ERROR! Distance value too big");
break;
}
}
//move machine to the exact new coordinate, because rounding makes a small error
/* removed for test
if ((newX-Xpos) >= 1) motorX.step(newX - Xpos, FORWARD, SINGLE);
if ((newX-Xpos) <= -1) motorX.step(Xpos - newX, BACKWARD, SINGLE);
if ((newY-Ypos) >= 1) motorY.step(newY - Ypos, FORWARD, SINGLE);
if ((newY-Ypos) <= -1) motorY.step(Ypos - newY, BACKWARD, SINGLE);
*/
//update the machine current position
Xpos = newX;
Ypos = newY;
Serial.print("----> \t");
Serial.print(Xpos);
Serial.print(":");
Serial.println(Ypos);
}
