Hi everybody.
I´m making a school project and i wanted to do a CNC, but to begin i decided to start small.
I wanted to make two motors make a square with a pencil.
I am using a CNC Shield, 2.5A steppers and a Arduino UNO, and, it seems that, all the tutorials on the internet that dont use GRBL, don´t work at all.
I just wanted a simple code that worked but that seems impossible to find.
If you got any questions you can ask me.
I would really appreciate if someone could help me with this.
Thanks! 
Are you using the GRBL/shield pinouts?
Something like
//------------------------------------------------------------------------------
// 2 Axis CNC Demo
// dan@marginallyclever.com 2013-08-30
//------------------------------------------------------------------------------
// Copyright at end of file.
// please see http://www.github.com/MarginallyClever/GcodeCNCDemo for more information.
//
// Modified for Wokwi at https://wokwi.com/projects/327761195587076690
// to use A4988 stepper drivers https://docs.wokwi.com/parts/wokwi-a4988
// copied from https://github.com/MarginallyClever/GcodeCNCDemo/blob/master/GcodeCNCDemo2Axis/GcodeCNCDemo2Axis.ino
// with modifications to parseNumber, serialBuffer, drivers
//
// David Forrest 2022-04-01
#include "config.h"
//------------------------------------------------------------------------------
// GLOBALS
//------------------------------------------------------------------------------
char serialBuffer[MAX_BUF]; // where we store the message until we get a newline
int sofar; // how much is in the serialBuffer
float px, py; // location
// speeds
float fr = 0; // human version
long step_delay; // machine version
// settings
char mode_abs=1; // absolute mode?
//------------------------------------------------------------------------------
// METHODS
//------------------------------------------------------------------------------
/**
* delay for the appropriate number of microseconds
* @input ms how many milliseconds to wait
*/
void pause(long ms) {
delay(ms/1000);
delayMicroseconds(ms%1000); // delayMicroseconds doesn't work for values > ~16k.
}
/**
* Set the feedrate (speed motors will move)
* @input nfr the new speed in steps/second
*/
void feedrate(float nfr) {
if(fr==nfr) return; // same as last time? quit now.
if(nfr>MAX_FEEDRATE || nfr<MIN_FEEDRATE) { // don't allow crazy feed rates
Serial.print(F("New feedrate must be greater than "));
Serial.print(MIN_FEEDRATE);
Serial.print(F("steps/s and less than "));
Serial.print(MAX_FEEDRATE);
Serial.println(F("steps/s."));
return;
}
step_delay = 1000000.0/nfr;
fr = nfr;
}
/**
* Set the logical position
* @input npx new position x
* @input npy new position y
*/
void position(float npx,float npy) {
// here is a good place to add sanity tests
px=npx;
py=npy;
}
/**
* Uses bresenham's line algorithm to move both motors
* @input newx the destination x position
* @input newy the destination y position
**/
void line(float newx,float newy) {
long i;
long over= 0;
long dx = newx-px;
long dy = newy-py;
int dirx = dx>0?1:-1;
#ifdef INVERT_Y
int diry = dy>0?-1:1; // because the motors are mounted in opposite directions
#else
int diry = dy>0?1:-1;
#endif
dx = abs(dx);
dy = abs(dy);
if(dx>dy) {
over = dx/2;
for(i=0; i<dx; ++i) {
m1step(dirx);
over += dy;
if(over>=dx) {
over -= dx;
m2step(diry);
}
pause(step_delay);
}
} else {
over = dy/2;
for(i=0; i<dy; ++i) {
m2step(diry);
over += dx;
if(over >= dy) {
over -= dy;
m1step(dirx);
}
pause(step_delay);
}
}
px = newx;
py = newy;
}
// returns angle of dy/dx as a value from 0...2PI
float atan3(float dy,float dx) {
float a = atan2(dy,dx);
if(a<0) a = (PI*2.0)+a;
return a;
}
// This method assumes the limits have already been checked.
// This method assumes the start and end radius match.
// This method assumes arcs are not >180 degrees (PI radians)
// cx/cy - center of circle
// x/y - end position
// dir - ARC_CW or ARC_CCW to control direction of arc
void arc(float cx,float cy,float x,float y,float dir) {
// get radius
float dx = px - cx;
float dy = py - cy;
float radius=sqrt(dx*dx+dy*dy);
// find angle of arc (sweep)
float angle1=atan3(dy,dx);
float angle2=atan3(y-cy,x-cx);
float theta=angle2-angle1;
if(dir>0 && theta<0) angle2+=2*PI;
else if(dir<0 && theta>0) angle1+=2*PI;
theta=angle2-angle1;
// get length of arc
// float circ=PI*2.0*radius;
// float len=theta*circ/(PI*2.0);
// simplifies to
float len = abs(theta) * radius;
int i, segments = ceil( len * MM_PER_SEGMENT );
float nx, ny, angle3, scale;
for(i=0;i<segments;++i) {
// interpolate around the arc
scale = ((float)i)/((float)segments);
angle3 = ( theta * scale ) + angle1;
nx = cx + cos(angle3) * radius;
ny = cy + sin(angle3) * radius;
// send it to the planner
line(nx,ny);
}
line(x,y);
}
/**
* Look for character /code/ in the buffer and read the float that immediately follows it.
* @return the value found. If nothing is found, /val/ is returned.
* @input code the character to look for.
* @input val the return value if /code/ is not found.
**/
float parseNumber(char code,float val) {
char *ptr=serialBuffer; // start at the beginning of buffer
while((long)ptr > 1 && (*ptr) && (long)ptr < (long)serialBuffer+sofar) { // walk to the end
if(*ptr==code) { // if you find code on your walk,
return atof(ptr+1); // convert the digits that follow into a float and return it
}
ptr=strchr(ptr,' ')+1; // take a step from here to the letter after the next space
}
return val; // end reached, nothing found, return default val.
}
/**
* write a string followed by a float to the serial line. Convenient for debugging.
* @input code the string.
* @input val the float.
*/
void output(const char *code,float val) {
Serial.print(code);
Serial.println(val);
}
/**
* print the current position, feedrate, and absolute mode.
*/
void where() {
output("X",px);
output("Y",py);
output("F",fr);
Serial.println(mode_abs?"ABS":"REL");
}
/**
* display helpful information
*/
void help() {
Serial.print(F("GcodeCNCDemo2AxisV1 "));
Serial.println(VERSION);
Serial.println(F("Commands:"));
Serial.println(F("G00 [X(steps)] [Y(steps)] [F(feedrate)]; - line"));
Serial.println(F("G01 [X(steps)] [Y(steps)] [F(feedrate)]; - line"));
Serial.println(F("G02 [X(steps)] [Y(steps)] [I(steps)] [J(steps)] [F(feedrate)]; - clockwise arc"));
Serial.println(F("G03 [X(steps)] [Y(steps)] [I(steps)] [J(steps)] [F(feedrate)]; - counter-clockwise arc"));
Serial.println(F("G04 P[seconds]; - delay"));
Serial.println(F("G90; - absolute mode"));
Serial.println(F("G91; - relative mode"));
Serial.println(F("G92 [X(steps)] [Y(steps)]; - change logical position"));
Serial.println(F("M18; - disable motors"));
Serial.println(F("M100; - this help message"));
Serial.println(F("M114; - report position and feedrate"));
Serial.println(F("All commands must end with a newline."));
}
/**
* Read the input buffer and find any recognized commands. One G or M command per line.
*/
void processCommand() {
int cmd = parseNumber('G',-1);
switch(cmd) {
case 0:
case 1: { // line
feedrate(parseNumber('F',fr));
line( parseNumber('X',(mode_abs?px:0)) + (mode_abs?0:px),
parseNumber('Y',(mode_abs?py:0)) + (mode_abs?0:py) );
break;
}
case 2:
case 3: { // arc
feedrate(parseNumber('F',fr));
arc(parseNumber('I',(mode_abs?px:0)) + (mode_abs?0:px),
parseNumber('J',(mode_abs?py:0)) + (mode_abs?0:py),
parseNumber('X',(mode_abs?px:0)) + (mode_abs?0:px),
parseNumber('Y',(mode_abs?py:0)) + (mode_abs?0:py),
(cmd==2) ? -1 : 1);
break;
}
case 4: pause(parseNumber('P',0)*1000); break; // dwell
case 90: mode_abs=1; break; // absolute mode
case 91: mode_abs=0; break; // relative mode
case 92: // set logical position
position( parseNumber('X',0),
parseNumber('Y',0) );
break;
default: break;
}
cmd = parseNumber('M',-1);
switch(cmd) {
case 18: // disable motors
disable();
break;
case 100: help(); break;
case 114: where(); break;
default: break;
}
}
/**
* prepares the input buffer to receive a new message and tells the serial connected device it is ready for more.
*/
void ready() {
sofar=0; // clear input buffer
Serial.print(F(">")); // signal ready to receive input
}
/**
* First thing this machine does on startup. Runs only once.
*/
void setup() {
Serial.begin(BAUD); // open coms
setup_controller();
position(0,0); // set staring position
feedrate((MAX_FEEDRATE + MIN_FEEDRATE)/2); // set default speed
help(); // say hello
ready();
}
/**
* After setup() this machine will repeat loop() forever.
*/
void loop() {
// listen for serial commands
while(Serial.available() > 0) { // if something is available
char c=Serial.read(); // get it
Serial.print(c); // repeat it back so I know you got the message
if(sofar<MAX_BUF-1) serialBuffer[sofar++]=c; // store it
if((c=='\n') || (c == '\r')) {
// entire message received
serialBuffer[sofar]=0; // end the buffer so string functions work right
Serial.print(F("\r\n")); // echo a return character for humans
processCommand(); // do something with the command
ready();
}
}
}
/**
* This file is part of GcodeCNCDemo.
*
* GcodeCNCDemo is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* GcodeCNCDemo is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Foobar. If not, see <http://www.gnu.org/licenses/>.
*/
or
Please read and use this link: How to get the best out of this forum - Using Arduino / Project Guidance - Arduino Forum
To write code that uses the CNC shield you must first know the pin mapping between the CNC shield and the Uno. Here is that pin mapping.
The CNC shield has the stepper drivers disabled by default. To enable the steppers one must set pin 8 as an OUTPUT and low or jumper the EN/GND header.
With what stepper drivers is the CNC shield equiped? The A4988 drivers are good for 1A with out heat sink and 1.5A with heat sink and fan cooling. DRV8825 drivers are good for 1.5A with out heat sink and 2.0A with heat sink and fan cooling. I know of no drivers that are directly compatible that will safely provide 2.5A per coil.
Whichever driver that you have, it is imperative that the coil current be properly set. How to set coil current on various drivers.
Stepper libraries will greatly aid in programming steppers. I like the MobaTools stepper library. It is available via the IDE library manager.
Thanks.
I'll read it when i have time :]
Please describe or show a drawing of the PHYSICAL part of your project, so we can see how the stepper motors will move your pencil.
I'll reply when You've done it.