billie
/
www.billiegoose.xyz


			
							123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290291292293294295296297298299300301302303304305306307308309310311312313314315316317318319320321322323324325326327328329330331332333334335336337338339340341342343344345346347348349350351352353354355356357358359360361362363364365366367368369370371372373374375376377378379380381382383384385386387388389390391392393394395396397398399400401402403404405406407408409410411412413414415416417418419420421422423424425426427428429430431432433434435436437438439440441442443444445446447448449450451452453454455456457458459460461462463464465466467468469470471472473474475476477478479480481482483484485486487488489490491492493494495496497498499500501502503504505506507508509510511512513514515516517518519520521522523524525526527528529530531532533534535536537538539540541542543544545546547548549550551552553554555556557558559560561562563564565566567568569570571572573574575576577578579580581582583584585586587588589590591592593594595596597598599600601602603604605606607608609610611612613614615616617618619620621622623624625626627628629630631632633634635636637638639640641642643644645646647648649650651652653654655656657658659660661662663664665666667668669670671672673674675676677678679680681682683684685686687688689690691692693694695696697698699700701702703704705706707708709710711712713714715716717718719720721722723724725726727728729730731732733734735736737738739740741742743744745746747748749750751752753754755756757758759760761762763764765766767768769770771772773774775776777778779780781782783784785786787788789790791792793794795796797798799800801802
							<!--
layout: false
-->
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" lang="en">

<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<!--
Useful websites:
Comparison of Canvas and SVG
http://people.mozilla.com/~vladimir/xtech2006/

Canvas Tutorial
https://developer.mozilla.org/en/Canvas_tutorial/

Animating with Javascript + Canvas
http://dev.opera.com/articles/view/blob-sallad-canvas-tag-and-javascrip/
-->
<title>CNC Simulator</title>

<script type="text/javascript">
// Global variables
var temp = "";
var start_second = 0;
var intervalID = 0;
var running = true;
var seconds = 0; // 6 degrees
var time_inc = 1; // in seconds
var sec_hand_length = 70;
var min_hand_length = 65;
var hour_hand_length = 35;
var clock_radius = 75;


// Function to run as soon as page loads
function init()
{
    var d = new Date();
    var curr_hour = d.getHours();
    var curr_min = d.getMinutes();
    start_second = d.getSeconds();
    seconds = start_second + 60*curr_min + 60*60*((curr_hour) % 12);
    intervalID = window.setInterval(animate,1000);
    
    // Initialize the canvas.
    
}


// Animate one frame of the animation
function animate()
{
    var canvas = document.getElementById("cnc_canvas");
    var ctx = canvas.getContext("2d");
    var sec_angle = 0;
    var min_angle = 0;
    var hour_angle = 0;
    //alert("Breakpoint animate");
    // Always put the terminating code near the top in case there is an error later on and the function exits before it can stop the interval timer.
    seconds = seconds + time_inc;
    //if (seconds % 60 > (3+start_second) % 60) {
    //    stop();
    //}
    
    with (ctx) {
        // What? No "clear canvas" command?
        clearRect(0,0,400,600);
        
        // Draw clock face
        strokeStyle = "black";
        lineWidth = 1;
        beginPath();
        arc(100, 100, clock_radius, 0.001, 2*Math.PI, false);
        //alert("Breakpoint arc");
        stroke();
        //alert("Breakpoint stroke");
        
        // Draw second hand.
        lineWidth = 1;
        strokeStyle = "green";
        beginPath();
        moveTo(100,100);
        sec_angle = 180-360/60*seconds;
        //alert("Breakpoint sec_angle = " + String(sec_angle));
        temp = "x = " + String(100+sec_hand_length*Sin(sec_angle)) + " y = " + String(100+sec_hand_length*Cos(sec_angle));
        //alert("Breakpoint " + temp);        
        lineTo(100+sec_hand_length*Sin(sec_angle), 100+sec_hand_length*Cos(sec_angle));
        //alert("Breakpoint lineTo");
        stroke();
        
        // Draw minute hand.
        beginPath();
        strokeStyle = "red";
        lineWidth = 2;
        moveTo(100,100);
        min_angle = 180-360/60*seconds/60;
        lineTo(100+min_hand_length*Sin(min_angle), 100+min_hand_length*Cos(min_angle));
        stroke();
        
        // Draw hour hand.
        lineWidth = 3;
        strokeStyle = "blue";
        beginPath();
        moveTo(100,100);
        hour_angle = 180-360/12*seconds/60/60;
        lineTo(100+hour_hand_length*Sin(hour_angle), 100+hour_hand_length*Cos(hour_angle));
        stroke();
    }
}

function stop() {
    window.clearInterval(intervalID);
    running = false;
}
function start() {
    time_inc = 1;
    // Only start if we're not already running an animation.
    if (!running) {
        running = true;
        intervalID = window.setInterval(animate,1000);
    }
}
function start_high_speed() {
    // If we're not already running an animation.
    if (running) {
        // Kill previous interval
        stop();
    }
    time_inc = 15;
    running = true;
    intervalID = window.setInterval(animate,10);        
}

function d2r(degrees) {
    return degrees*Math.PI/180;
}
function Sin(degrees) {
    return Math.sin(d2r(degrees));
}
function Cos(degrees) {
    return Math.cos(d2r(degrees));
}
</script>


<style type="text/css">
td {
    padding-top: 10px;
}
</style>
</head>

<body onload="init()">
<h2 style="margin-bottom: 0">CNC Simulator</h2>
<table>
 <tr>
  <td style="vertical-align: top" >
   <div style="border-width: 5px; border-style: ridge;">
    <p style="font-weight: bold; margin: 10px">
     <span id="x_disp">X:</span>
     <br />
     <span id="y_disp">Y:</span>
     <br />
     <span id="z_disp">Z:</span>
     <br />
     <span id="time_disp">Time:</span>
    </p>
   </div>
   <form action="">
    <table>
     <tr>
      <td>
        <label for="ppi_input">Pixels per inch:</label>
        <br />
        <input id="ppi_input" type="text" value="127" style="width: 5em" />
      </td>
      <td>
       <label for="time_step_input">Time step:</label>
       <br />
       <input id="time_step_input" type="text" value="1" style="width: 5em" />
      </td>
     </tr>
     <tr>
      <td>
        <label for="speed_input">Speed factor:</label>
        <br />
        <input id="speed_input" type="text" value="5" style="width: 5em; margin-right: 5em;" />
      </td>
      <td>
        <label for="blitz_input">Blitz mode:</label>
        <input type="checkbox" id="blitz_input" checked="checked" />
      </td>
     </tr>
     <tr>
      <td>
        <label for="offset_x">Offset X:</label>
        <br />
        <input id="offset_x" type="text" value="50" style="width: 5em; margin-right: 5em;" />
      </td>
      <td>
        <label for="offset_y">Offset Y:</label>        
        <br />
        <input id="offset_y" type="text" value="50" style="width: 5em; margin-right: 5em;" />
      </td>
     </tr>
     <tr>
      <td colspan="2">
    <label for="code_input">Enter CNC code here:<br/></label>
    <textarea rows="20" cols="50" id="code_input">START MM  01 // Use millimeters, program ID 01
 TD=   3.175 // Tool diameter: 1/8 in = 3.175 mm
FR XY  =03.7 // Divided the suggested feedrate by two, because tool was flexing.
FR Z   =01.2 // Feedrate based on 1 cutting edge, instead of 4, then slightly reduced.
SETUP >zcxyu // Allow user to position tool above 1st hole.
REPEAT    02 // Second traverse gets the edges better
GOfX   0.000 // Go to 1st hole
GOfY   0.000 //
GO Z-  6.000 // Drill 1st hole
Z>C          // Raise tool
CALL SUB  10 // Cut left side...
ZERO AT      // (Set origin to right hole)
   X  47.000 // * Change depending on connector *
   Y   0.000 //
CALL SUB  11 // ...Cut right side...
ZERO AT      // (Reset origin to left hole)
   X- 47.000 // * Change depending on connector *              
   Y   0.000 //
GO X   6.920 // ...And return to Point 1.
   Y   3.410 //
Z>C          // Raise tool
GOfX  47.000 // Go to 2nd hole * Change depending on connector *
   Y   0.000 //
GO Z  -6.000 // Drill 2nd hole
Z>C          // Raise tool
REPEAT END   //
END NEW PART //

SUB 10       // Left Side (located on line 050)
GO X   6.920 // Point 1
   Y   3.410 //
GO Z-  9.000 // Insert tool
ARC          // Point 2
 XC=   6.920 //
 YC=   1.500 //
  a= 101.470 //
GO X   5.740 // Point 3
   Y-  2.280 //
ARC          // Point 4
 XC=   7.120 //
 YC=-  2.000 //
  a=  79.530 //
SUB RETURN   //

SUB 11       // Right Side (located on line 100)
GO X-  7.120 // Point 5
   Y-  3.410 //
ARC          // Point 6
 XC=-  7.120 //
 YC=-  2.000 //
  a=  79.530 //
GO X-  5.050 // Point 7
   Y   1.120 //
ARC          // Point 8
 XC=-  6.920 //
 YC=   1.500 //
  a= 101.470 //
SUB RETURN   //
    </textarea>
    <br/>
     <input name="submit" type="button" value="Click To Run Simulator" onclick="startSimulation();"/>
     <input id="pause_input" type="button" value="Pause"  onclick="pause();" />
    </td>
    </tr>
    </table>
    </form>
   </td>
   <td style="vertical-align:top">
    <canvas id="cnc_canvas" width="780" height="650" style="border:1px solid black"></canvas>
   </td>
 </tr>
</table>
<hr />
<div class="output_wrapper" >
 <b>Output:</b>
 <pre id="output"></pre>
</div>
<script type="text/javascript">
// The so-called Prototype Dollar function, a shortcut for document.getElementById()
function $() {
    var elements = new Array();
    for (var i = 0; i < arguments.length; i++) {
        var element = arguments[i];
        if (typeof element == "string")
            element = document.getElementById(element);
        if (arguments.length == 1)
            return element;
        elements.push(element);
    }
    return elements;
}
ctx = null;
canvas = null;
function clear_vars() {// Global variables
    unit = "MM"; // or "IN"
    time_step = 1; // update every half second.
    ppi = 96; // Pixels per inch
    cf = 1; // Pixel to unit ratio
    td = 1; // Tool diameter
    max_frx = 1; // Maximum feed rate X
    max_fry = 1; // Maximum feed rate Y
    max_frz = 1; // Maximum feed rate Z
    x_inc = 1; // Distance to move per tick
    y_inc = 1; // Distance to move per tick
    z_inc = 1; // Distance to move per tick
    a_inc = 1; // Distance to move per tick
    mar_x = 10; // Horizontal margin of origin
    mar_y = 10; // Vertical margin of origin
    tool_c = 2; // Clearance height.
    tool_x = 0; // Tool position X
    tool_y = 0; // Tool position Y
    tool_z = 0; // Tool position Z
    tool_a = 0; // Tool angle (used for arcs)
    arc_r = 0;  // Radius of currently drawn arc.
    arc_dir = false; // Counter-clockwise
    old_x = 0;  // Previous tool position X
    old_y = 0;  // Previous tool position Y
    old_z = 0;  // Previous tool position Z
    old_a = 0;  // Previous tool angle (used for arcs)
    goal_x = 0; // Destination coordinate
    goal_y = 0; // Destination coordinate
    goal_z = 0; // Destination coordinate
    xc = 0; // Used for drawing arcs
    yc = 0; // Used for drawing arcs
    ac = 0; // Used for drawing arcs
    time = 0;   // Time needed to execute cut.
    time_x = 0;
    time_y = 0;
    time_z = 0;
    time_a = 0; // Used for arcs
    time_elapsed = 0;
    n = 0;      // Line index
    lines = []; // Array of each line of code
    line = "";  // Current line
    moving = false; // Set to true when the tool is moving from one point to another.
    arcing = false; // Set to true when the tool is arcing.
    interval_id = 0; // Variable needed to stop the timer during real-time mode
    blitz_done = false; // Variable used to stop the timer in blitz mode.   
    paused = false; // Pause/unpaused state
    speed = 1;
    stack = []; // Line numbers to return to
    canvas_stack = 0; // How many times restore() the canvas
    canvas = $("cnc_canvas");
    ctx = canvas.getContext("2d");   
}
function startSimulation() {
    // Clean up variables from the last run.
    clear_vars();
    // Clear debug output
    $("output").innerHTML = "";
    // Because the previous run might not have finished
    for (var i = 0; i < 50; i++) {
        ctx.restore();
    }
    // Stop the clock
    stop();
    // Since there is no "clear canvas" command.
    ctx.fillStyle = "white"
    ctx.fillRect(0, 0, canvas.width, canvas.height);
    ctx.strokeStyle = "black";
    /*
    The canvas has it's origin in the top-left corner, but the CNC
    Machine has it's origin in the bottom-left corner. Therefore,
    we translate the origin and apply a transformation matrix to
    flip the Y direction.
    */   
    ctx.save();
    canvas_stack = canvas_stack + 1;
    ctx.transform(1, 0, 0, -1, 0, 0);  
    mar_x = parseFloat($("offset_x").value);
    mar_y = parseFloat($("offset_y").value);
    ctx.translate(mar_x, mar_y-canvas.height); 
    ctx.save();
    canvas_stack = canvas_stack + 1;
    
    lines = $("code_input").value.split("\n"); //str.split("\n");
    ppi = parseFloat($("ppi_input").value);    
    // Start the animation sequence
    n = -1;    
    debugn("There are " + lines.length + " lines");
    // Stop all animations
    window.clearInterval(interval_id);
    paused = true;
    pause();
}
function pause() {
    if (paused) {
        paused = false;
        // Set the speed
        speed = parseFloat($("speed_input").value);
        time_step = parseFloat($("time_step_input").value);
        // Start the CNC simulation.
        if ($("blitz_input").checked) {
            while (blitz_done == false) {
                tick();
            }
        } else {
            interval_id = window.setInterval(tick,1000*time_step/speed);
        }
        $("pause_input").value = "Pause";
    } else {
        paused = true;
        window.clearInterval(interval_id);
        $("pause_input").value = "Resume";
    }
}
function nextLine() {
    n = n + 1;
    if (n >= lines.length) {
        return false;
    } else {
        line = lines[n];
        return true;
    }
}
function startsWith(s1, s2) {
    if (s1.substr(0,s2.length) == s2) {
        return true;
    } else {
        return false;
    }
}
function deg2rad(d) {
    return (Math.PI/180)*d;
}
function rad2deg(r) {
    return (180/Math.PI)*r;
}
function tick() {    
    if (moving) {
        // Store previous position
        old_x = tool_x;
        old_y = tool_y;
        old_z = tool_z;
        old_a = tool_a;
        // Figure out new position
        if (time < time_step) {
            if (arcing) {
                tool_a = goal_a;
                tool_x = xc + Math.cos(tool_a)*arc_r;
                tool_y = yc + Math.sin(tool_a)*arc_r;
            } else {
                tool_x = goal_x;
                tool_y = goal_y;
                tool_z = goal_z;
            }
            time_elapsed = time_elapsed + time;
        } else {
            if (arcing) {
                tool_a = tool_a + a_inc;
                tool_x = xc + Math.cos(tool_a)*arc_r;
                tool_y = yc + Math.sin(tool_a)*arc_r;
            } else {
                tool_x = tool_x + x_inc;
                tool_y = tool_y + y_inc;
                tool_z = tool_z + z_inc;
            }
            time_elapsed = time_elapsed + time_step;
        }              
        // Update display
        $("x_disp").innerHTML = "X: " + tool_x;
        $("y_disp").innerHTML = "Y: " + tool_y;
        $("z_disp").innerHTML = "Z: " + tool_z;
        $("time_disp").innerHTML = "Time: " + time_elapsed;
        
        // Draw line if tool is below surface.
        if (tool_z < 0) {
            with (ctx) {            
                // Draw hole
                beginPath();
                fillStyle = "black";
                arc(tool_x, tool_y, td/2.0, 0, Math.PI*2.0, true);
                fill();
                // Draw line
                lineCap = "round";
                lineWidth = td;
                beginPath();
                strokeStyle = "black";
                if (arcing) {                    
                    arc(xc, yc, arc_r, old_a, tool_a, arc_dir);
                } else {                    
                    moveTo(old_x, old_y);                
                    lineTo((tool_x), (tool_y));
                }
                stroke();                  
            }
        } else {
            // Draw hollow dot (so we can see the path of the tool)
            with (ctx) {  
                lineWidth = 1/cf;
                strokeStyle = "blue";
                strokeRect((tool_x)-1/cf, (tool_y) -1/cf, 3/cf, 3/cf);
            }
        }
        // Decrease time
        time = time - time_step;
        // Finish line
        if (time < 0) {
            time = 0;
            moving = false;
            arcing = false;
        }
        debug(".");
    } else {
        // Always safest to put this first, in case of unhandled syntax
        // errors later on in the code.
        if (nextLine()) {
            ndebug("Line " + n + ": ");
        } else {
            ndebug("Ended because there are no more lines.");
            n = -1;
            ndebug("canvas_stack = " + canvas_stack);
            for (var i = 0; i < canvas_stack; i++) {
                ndebug("ctx.restore()");
                ctx.restore();
            }
            blitz_done = true;
            window.clearInterval(interval_id);
            return;
        }
        //debug(line);
        if (startsWith(line, "START")) {
            // Set unit
            unit = line.substr(6,2);
            debugd("Unit: " + unit);
            if (unit == "MM") {
                debugd("Millimeters");
                cf = ppi / 25.4;
            } else if (unit == "IN") {
                debugd("Inches");
                cf = ppi;
            } else {
                ndebug("Invalid unit");
                n = lines.length;
                return;
            }
            debug("Scale: " + cf);
            ctx.scale(cf, cf);
        } else if (startsWith(line, " TD=")) {
            // Set tool diameter
            debugd("Tool Diameter: " + line.substring(4,12));
            td = parseFloat(line.substring(4,12));
            ctx.lineWidth = td;            
            debug("ctx.lineWidth = " + ctx.lineWidth);
        } else if (startsWith(line, "FR")) {
            // TODO: set feed rate
            debugd("Setting feed rate for " + line.substr(3,3) + " to " + line.substring(8,12));
            if (line.indexOf("X") != -1) {
                max_frx = parseFloat(line.substring(8,12));
                debug(" set FR X = " + max_frx);
            }
            if (line.indexOf("Y") != -1) {
                max_fry = parseFloat(line.substring(8,12));
                debug(" set FR Y = " + max_fry);
            }
            if (line.indexOf("Z") != -1) {
                max_frz = parseFloat(line.substring(8,12));
                debug(" set FR Z = " + max_frz);
            }
        } else if (startsWith(line, "SETUP")) {
            // This step doesn't translate well, and would get annoying
            debug("Setup: " + line.substring(7,12));
            debug(" Note: in real life, this command would let you position the tool at a new 'zero' position.");
        } else if (startsWith(line, "Z>C")) {
            tool_z = tool_c;
            debug("Z>C: Z = " + String(tool_c));
        } else if (startsWith(line, "GO")) {
            goal_x = tool_x; time_x = 0;
            goal_y = tool_y; time_y = 0;
            goal_z = tool_z; time_z = 0;
            debugd("Go");
            do {
                if (line.substr(3,1) == "f") {
                    // TODO: how fast is "fast" anyway?
                }
                if (line.substr(3,1) == "X") {
                    goal_x = parseFloat(line.substring(5,12));
                    if (line.substr(4,1) == "-") {
                        goal_x = -goal_x;
                    }                    
                    time_x = Math.abs((goal_x - tool_x) / max_frx);
                    debugd("X coor: " + goal_x);
                } else if (line.substr(3,1) == "Y") {
                    goal_y = parseFloat(line.substring(5,12));
                    if (line.substr(4,1) == "-") {
                        goal_y = -goal_y;
                    }
                    time_y = Math.abs((goal_y - tool_y) / max_fry);
                    debugd("Y coor: " + goal_y);
                } else if (line.substr(3,1) == "Z") {                    
                    goal_z = parseFloat(line.substring(5,12));                    
                    if (line.substr(4,1) == "-") {
                        goal_z = -goal_z;
                    }
                    time_z = Math.abs((goal_z - tool_z) / max_frz);
                    debugd("Z coor: " + goal_z);
                }
                n = n+1;
                if (n >= lines.length) {
                    break;
                }
                line = lines[n];
            } while (line.substr(0,2) == "  ")
            n = n - 1;
            // Compute how many seconds it will take to execute this cut
            time = Math.max(Math.max(time_x, time_y), time_z);
            debugd("Time Required: "+time);
            x_inc = (goal_x - tool_x) / time * time_step;
            y_inc = (goal_y - tool_y) / time * time_step;
            z_inc = (goal_z - tool_z) / time * time_step;
            debug("X inc: " + x_inc + " Y inc: " + y_inc +" Z inc: " + z_inc);
            moving = true;
        } else if (startsWith(line, "ZERO AT")) {
            // Translate the canvas origin
            debugd("ZERO AT");
            goal_x = 0; time_x = 0;
            goal_y = 0; time_y = 0;
            goal_z = 0; time_z = 0;
            if (!nextLine()) { return; }
            while (line.substr(0,2) == "  ") {
                if (line.substr(3,1) == "X") {
                    goal_x = parseFloat(line.substring(5,12));
                    if (line.substr(4,1) == "-") {
                        goal_x = -goal_x;
                    }
                    debug(" X coor: " + goal_x);
                } else if (line.substr(3,1) == "Y") {
                    goal_y = parseFloat(line.substring(5,12));                   
                    if (line.substr(4,1) == "-") {
                        goal_y = -goal_y;
                    }
                    debug(" Y coor: " + goal_y);
                } else if (line.substr(3,1) == "Z") {                    
                    goal_z = parseFloat(line.substring(5,12));                    
                    if (line.substr(4,1) == "-") {
                        goal_z = -goal_z;
                    }
                    debug(" Z coor: " + goal_z);
                }
                if (!nextLine()) { break; }
            } 
            n = n - 1;
            // Translate the canvas origin
            ctx.save();            
            ctx.translate(goal_x, goal_y);
            canvas_stack = canvas_stack + 1;
            // Untranslate tool
            tool_x = tool_x - goal_x;
            tool_y = tool_y - goal_y;
        } else if (startsWith(line, "ARC")) {
            debugd("ARC");
            if (!nextLine()) { return; }
            if (line.substr(0,4) == " XC=") {
                xc = parseFloat(line.substring(5,12));
                if (line.substr(4,1) == "-") {
                    xc = -xc;
                }
                debug(" XC: " + xc);
            } else {
                debug("I really expected a line starting with ' XC='");
            }
            if (!nextLine()) { return; }
            if (line.substr(0,4) == " YC=") {
                yc = parseFloat(line.substring(5,12));
                if (line.substr(4,1) == "-") {
                    yc = -yc;
                }
                debug(" YC: " + yc);
            } else {
                debug("I really expected a line starting with ' YC='");
            }
            if (!nextLine()) { return; }
            if (line.substr(0,4) == "  a=") {
                // I call the variable 'ac' for resemblance
                ac = parseFloat(line.substring(5,12));
                if (line.substr(4,1) == "-") {
                    ac = -ac;
                    arc_dir = true;
                } else {
                    arc_dir = false;
                }
                debugd(" AC: " + ac);                
                ac = deg2rad(ac);
                debugd("in radians: " + ac); 
            } else {
                debug("I really expected a line starting with '  a='");
            }
            arc_r = Math.sqrt( Math.pow(xc-tool_x, 2) +
                               Math.pow(yc-tool_y, 2) );
            debugd("R = " + arc_r);
            var dist = Math.abs(arc_r*ac);
            var xyfr = (max_frx + max_fry)/2;
            time = dist/xyfr;
            debugd("Time Required: " + time);            
            a_inc = ac/time*time_step;
            debugd("a_inc = " + a_inc);
            // Math.atan2 seems to be measuring Clockwise from the Y
            // axis. Ridiculous.
            tool_a = Math.atan2(tool_y-yc, tool_x-xc);
            debugd("tool_a = " + rad2deg(tool_a) + " degrees");
            goal_a = Math.atan2(tool_y-yc, tool_x-xc) + ac;
            debug("goal_a = " + rad2deg(goal_a) + " degrees");
            moving = true;
            arcing = true;
            //arcing = true;
        } else if (startsWith(line, "CALL SUB")) {
            // Push line # onto stack
            debugd("Calling Sub");
            stack.push(n);
            ctx.save();
            canvas_stack = canvas_stack + 1;
            // Get the SUB id
            var sub_id = line.substring(9,12).replace(" ","");
            var sub_id = "SUB " + sub_id;
            debugd("Scanning for '" + sub_id +"'");
            // Move the cursor location to the start of the subroutine.
            n = -1;
            while (n < lines.length) {
                n = n + 1;
                line = lines[n];
                if (line.substr(0,sub_id.length) == sub_id) {
                    debugd("Found '" + sub_id + "' on line " + String(n));
                    debug("Stack: " + String(stack));
                    break;
                }
            }                
        } else if (startsWith(line, "SUB RETURN")) {
            // Return to our line # in the stack.
            n = stack.pop();
            ctx.restore();
            canvas_stack = canvas_stack - 1;
            debugd("SUB RETURN return to line " + String(n));
            debug("Stack: " + String(stack));
        } else if (startsWith(line, "REPEAT END")) {
            if (stack.length > 0) {
                n = stack.pop();
                debug("REPEAT END return to line " + String(n));
            } else {
                debug("Passing REPEAT END");
            }
        } else if (startsWith(line, "REPEAT")) {
            var rep_num = parseInt(line.substring(10,12))
            debugd("REPEAT " + String(rep_num) + " times");
            for (var i = 1; i < rep_num; i++) {
                stack.push(n);
            }
            debug("Stack: " + String(stack));
        } else if (startsWith(line, "END")) {
            n = lines.length;
            debug("Encountered an END");
        } else {
            debug("Skipping line: " + line);
        }
    }  
}

/*
These are placed at the end, so if prior code has syntax errors,
the page will clearly be broken.
*/
function debug(str) {
    var obj;
    obj = $("output");
    obj.innerHTML = obj.innerHTML + str;
}
function ndebug(str) {
    var obj;
    obj = $("output");
    obj.innerHTML = obj.innerHTML + "\n" + str;
}
function debugn(str) {
    var obj;
    obj = $("output");
    obj.innerHTML = obj.innerHTML + str + "\n";
}
function ndebugn(str) {
    var obj;
    obj = $("output");
    obj.innerHTML = obj.innerHTML + "\n" + str + "\n";
}
function debugd(str) {
    var obj;
    obj = $("output");
    obj.innerHTML = obj.innerHTML + str + "... ";
}
</script>
<footer>
<hr/>
<p style="text-align: center; font-style:italic"><a href="http://validator.w3.org/#validate-by-upload">Freaking valid HTML5 baby!!!</a></p>
</footer>
</body>
</html>