In lots of brmlab projects (brmScope, LaserCutter) some kind of XY/cartesian robot is used. Goal of this project is to provide board and ATmega firmware as simple and cheap as possible designed to control stepper-motors-based XYZ robots.

This will include power transistors to drive motors and maybe some optocoders or at least zero-position sensors.

• http://www.gme.cz/tranzistorova-pole/uln2074-p380-007/ (unipolar steper driver)
• http://www.gme.cz/obvody-pro-rizeni-motoru-mustkove-budice/l293d-p399-017/ (bipolar steper driver)
• http://www.gme.cz/chladice-vyrobene-z-al-profilu/ick14-16l-p620-056/ (Heatsink for DIP16)
• http://www.gme.cz/svorkovnice-do-dps/ark500-3-b-p821-120/
• http://www.gme.cz/laboratorni-plosne-spoje-vrtane-jednostranne/univerzalni-spoj-160x100-rm-2-54-kulate-body-p661-054/
• http://www.gme.cz/oboustranne-koliky/oboustranny-kolik-s1g20w-2-54mm-p832-018/
• http://www.gme.cz/patice-dil/sokl-16-p823-002/
• http://www.gme.cz/napajeci-souose-konektory-do-dps/napajeci-souosy-konektor-wealthmetal-ds-241b-p806-303/
• http://www.gme.cz/napajeci-souose-konektory-do-dps/napajeci-souosy-konektor-k375a-p806-049/

• Firmware should use standart G-Code protocol! G-code
• Maybe we can just use some already writter universal state-of-the-art firmware for CNC like GRBL:
  • http://dank.bengler.no/-/page/show/5470_grbl
  • http://github.com/simen/grbl
  • http://www.linuxcnc.org/

Board could support both unipolar and bipolar steppers. just insert L293D instead of ULN and change jumper settings or something. We can also provide two IC sockets (one for ULN and second for L293D), then you will insert only one of those ICs to select if you want to drive unipolar or bipolar steppers

Or maybe we can just use only L293D (or some high-power alternative), because it can handle both bipolar and unipolar steppers.

According to http://robotika.cz/articles/steppers/ it's possible to use ULN as invertor to minimalize need of IO pins on microcontroller. Here's an example: I guess you can use something similar with L293D IC (if you don't need active braking).

cncdu.ino

#include <Stepper.h>
 
char InCmd[32];
byte InCmdIndex = 0;
byte InByte = 0;
unsigned long lastTime = 0;
int LaserPIN = 14;
int Ypojezd = 19;
int Xpojezd = 18;
int FDir = 17;
int FStep = 16;
 
unsigned posX = 0;
unsigned posY = 0;
 
#define STEPS 200
Stepper stepperX(STEPS, 4, 2, 3, 5);
Stepper stepperY(STEPS, 12, 10, 11, 13);
 
void setup() {
  Serial.begin(115200);
 
  stepperX.setSpeed(10);
  stepperY.setSpeed(10);
 
  pinMode(LaserPIN, OUTPUT);
  digitalWrite(LaserPIN, LOW);
  pinMode(Ypojezd, INPUT);
  digitalWrite(Ypojezd, HIGH);
  pinMode(Xpojezd, INPUT);
  digitalWrite(Xpojezd, HIGH);
 
  pinMode(FDir, OUTPUT);
  digitalWrite(FDir, LOW);
  pinMode(FStep, OUTPUT);
  digitalWrite(FStep, LOW);
 
 
 
}
 
void loop() {
  while(Serial.available()) {
    lastTime = millis();
    InByte = Serial.read();
    if (InCmdIndex >= sizeof(InCmd)){
      InCmdIndex = 0;
      Serial.println("INPUT COMMAND OVERFLOW");
    } 
 
    if (InByte == 10 || InByte == 13 ) {
      //Serial.println(sizeof(InCmd),DEC);
      ExeCmd(InCmd);
 
			for (InCmdIndex++; InCmdIndex>0; InCmdIndex--) {
       				InCmd[InCmdIndex] = 0;
       			}
 
      InCmdIndex = 0;
 
    }
    else{
      InCmd[InCmdIndex++] = InByte;
    }//		Serial.println(InCmdIndex, DEC);
  }
 
 
  if ( (lastTime + 15000) < millis() ) {
    digitalWrite(LaserPIN, LOW);
    digitalWrite(2, LOW);
    digitalWrite(3, LOW);
    digitalWrite(4, LOW);
    digitalWrite(5, LOW);
    digitalWrite(6, LOW);
    digitalWrite(7, LOW);
    digitalWrite(8, LOW);
    digitalWrite(9, LOW);
    digitalWrite(10, LOW);
    digitalWrite(11, LOW);
    digitalWrite(12, LOW);
    digitalWrite(13, LOW);
  }
}
 
void ExeCmd(char *InCmd){
  byte MotorIndex;
  byte MotorSpeed;
  int MotorSteps;
  byte SeqID;
  byte LaserPower;
  byte SCommand;
 
  SCommand = 0;	
  LaserPower = 0;
  SeqID = 0;
  MotorSteps = 0;
  MotorSpeed = 0;
  MotorIndex = 0;
  int toX = 0;
  int toY = 0;
 
  //	for (int i = 0;i<CmdIndex;i++){
  //		Serial.print(InCmd[i]);
  //	}
  //	Serial.println();
  //Serial.println(InCmd[0], DEC);
  switch (InCmd[0]){
 
  case 'm':
    while (*InCmd != ' ') InCmd++; 
    while (isspace(*InCmd)) InCmd++;
    if (atoi(InCmd) > 0 && atoi(InCmd) < 255){
      MotorIndex = atoi(InCmd);
      //Serial.println(MotorIndex, DEC);
    }
    else{
      Serial.println("Wrong Motor Index (1-254)");
      break;
    }		
 
    while (*InCmd != ' ') InCmd++; 
    while (isspace(*InCmd)) InCmd++;
    if (atoi(InCmd) > 0 && atoi(InCmd) < 255){
      MotorSpeed = atoi(InCmd);
      //Serial.println(MotorSpeed, DEC);
    }
    else{
      Serial.println("Wrong Motor Speed (1-254)");
      break;
    }
 
    while (*InCmd != ' ') InCmd++; 
    while (isspace(*InCmd)) InCmd++;
    if (atoi(InCmd) > -10001 && atoi(InCmd) < 10001	){
      MotorSteps = atoi(InCmd);
      //Serial.println(MotorSteps, DEC);
    }
    else{
      Serial.println("Wrong Steps (-10000 - +10000)");
      break;
    }
 
    while (*InCmd != ' ') InCmd++; 
    while (isspace(*InCmd)) InCmd++;
    if (atoi(InCmd) > 0 && atoi(InCmd) < 255){
      SeqID = atoi(InCmd);
      //Serial.println(SeqID, DEC);
    }
    else{
      Serial.println("Wrong Sequence ID (1-254)");
      break;
    }		
 
    switch (MotorIndex){
 
    case 1:
      stepperX.setSpeed(MotorSpeed);
      stepperX.step(MotorSteps);
      posX += MotorSteps;
      break;
 
    case 2:
      stepperY.setSpeed(MotorSpeed);
      stepperY.step(MotorSteps * 3);
      posY += MotorSteps;
      break;
 
 
    }
    Serial.println(SeqID, DEC);
    break;
 
  case 'l':
 
    while (*InCmd != ' ') InCmd++; 
    while (isspace(*InCmd)) InCmd++;
    if (atoi(InCmd) >= 0 && atoi(InCmd) < 255){
      LaserPower = atoi(InCmd);
      //Serial.println(LaserPower, DEC);
      if (LaserPower == 254) {
        digitalWrite(LaserPIN, HIGH);
      }
      else{
        digitalWrite(LaserPIN, LOW); 
      }
      //Serial.println(LaserPower, DEC);
    }
    else{
      Serial.println("Wrong Laser Power (0-254)");
      break;
    }		
 
    while (*InCmd != ' ') InCmd++; 
    while (isspace(*InCmd)) InCmd++;
    if (atoi(InCmd) > 0 && atoi(InCmd) < 255){
      SeqID = atoi(InCmd);
      //Serial.println(SeqID, DEC);
    }
    else{
      Serial.println("Wrong Sequence ID (1-254)");
      break;
    }		
 
    Serial.println(SeqID, DEC);
    break;
 
  case 's':
 
    while (*InCmd != ' ') InCmd++; 
    while (isspace(*InCmd)) InCmd++;
    if (atoi(InCmd) > 0 && atoi(InCmd) < 255){
      SCommand=(atoi(InCmd));
    }
    else{
      Serial.println("Wrong Command Number (1-254)");
      break;
    }
 
 
 
    while (*InCmd != ' ') InCmd++; 
    while (isspace(*InCmd)) InCmd++;
    if (atoi(InCmd) > 0 && atoi(InCmd) < 255){
      SeqID = atoi(InCmd);
      //Serial.println(SeqID, DEC);
    }
    else{
      Serial.println("Wrong Sequence ID (1-254)");
      break;
    } 
 
    switch (SCommand){
    case 1:
      XYReset();
      Serial.println(SeqID, DEC); 
      break;
    default:
      Serial.print("Unknow Command: ");
      Serial.println(SCommand,DEC );
      break;
    }
 
    break;
 
  case 'v':
    while (*InCmd != ' ') InCmd++; 
    while (isspace(*InCmd)) InCmd++;
    if (atoi(InCmd) > 0 && atoi(InCmd) < 255){
      MotorSpeed = atoi(InCmd);
      //Serial.println(MotorSpeed, DEC);
    }
    else{
      Serial.println("Wrong Motor Speed (1-254)");
      break;
    }
 
    while (*InCmd != ' ') InCmd++; 
    while (isspace(*InCmd)) InCmd++;
    if (atoi(InCmd) >= 0 && atoi(InCmd) < 10001	){
      toX = atoi(InCmd);
      //Serial.println(MotorSteps, DEC);
    }
    else{
      Serial.println("Wrong Steps (0 - +10000)");
      break;
    }
 
    while (*InCmd != ' ') InCmd++; 
    while (isspace(*InCmd)) InCmd++;
    if (atoi(InCmd) >= 0 && atoi(InCmd) < 10001	){
      toY = atoi(InCmd);
      //Serial.println(MotorSteps, DEC);
    }
    else{
      Serial.println("Wrong Steps (0 - +10000)");
      break;
    }
 
    while (*InCmd != ' ') InCmd++; 
    while (isspace(*InCmd)) InCmd++;
    if (atoi(InCmd) > 0 && atoi(InCmd) < 255){
      SeqID = atoi(InCmd);
      //Serial.println(SeqID, DEC);
    }
    else{
      Serial.println("Wrong Sequence ID (1-254)");
      break;
    } 
 
    stepperX.setSpeed(MotorSpeed);
    stepperY.setSpeed(MotorSpeed);
    line(posX, posY, toX, toY);
    Serial.println(SeqID, DEC);
    break;
 
 
  case 'h':
    PrintHelp();
    break;
 
    Serial.println(SeqID, DEC);
    break;
  default:
    Serial.println("WTF?");
    break;	
 
  }
 
 
}
 
void linej(int x1, int y1, int x2, int y2)
{
  int dx, dy, inx, iny, e, stepX, stepY;
 
  while(posX != x2 && posY != y2) {
    dx = x2 - x1;
    dy = y2 - y1;
 
    inx = dx > 0 ? 1 : -1;
    iny = dy > 0 ? 1 : -1;
 
    //stepperX.step(inx);
    posX += inx;
//    if(dx*(posY-y1)-(posX-x1)*dy*(dy*dx)>0) {
      if((float)posY/(float)y2 > (float)posX/(float)x2) {
      //stepperX.step(inx);
      posX += inx;
    } 
    else {
      //stepperY.step(iny);
      posY += iny;
    }
    Serial.print(posX, DEC);
    Serial.print(" ");
    Serial.println(posY, DEC);
  }
}
 
void line(int x1, int y1, int x2, int y2)
{
  int dx, dy, inx, iny, e, stepX, stepY;
 
  dx = x2 - x1;
  dy = y2 - y1;
  inx = dx > 0 ? 1 : -1;
  iny = dy > 0 ? 1 : -1;
  stepX = 0; 
  stepY = 0; 
 
  dx = abs(dx);
  dy = abs(dy);
 
  if(dx >= dy) {
    dy <<= 1;
    e = dy - dx;
    dx <<= 1;
    while (x1 != x2) {
      //			setpixel(x1, y1, color);
      if(e >= 0) {
        y1 += iny;
        stepperY.step(iny*3);
        e-= dx;
      }
      e += dy; 
      x1 += inx; 
      stepperX.step(inx);
    }
  } 
  else {
    dx <<= 1;
    e = dx - dy;
    dy <<= 1;
    while (y1 != y2) {
      //			setpixel(x1, y1, color);
      if(e >= 0) {
        x1 += inx;
        stepperX.step(inx);
        e -= dy;
      }
      e += dx; 
      y1 += iny; 
      stepperY.step(iny*3); 
    }
  }
 
  //	setpixel(x1, y1, color);
 
  posX = x1;
  posY = y1;
}
 
void XYReset(){
  posX = 0;
  posY = 0;
  stepperY.setSpeed(75);
  while (digitalRead(Ypojezd)==true){
    stepperY.step(-1);
  }
  stepperY.setSpeed(150);
  stepperY.step(1600);
 
  stepperX.setSpeed(75);
  while (digitalRead(Xpojezd)==true){
    stepperX.step(-1);
  }
  stepperX.setSpeed(150);
  stepperX.step(600);
 
}
 
void PrintHelp(){
/*  Serial.println("-----------------------------------------"); 
  Serial.println("----------BrmLab Laser Bordel------------"); 
  Serial.println("-----------------------------------------"); 
  Serial.println(); 
  Serial.println("Toto by mela byt napoveda....."); 
  Serial.println("A casem take mozna bude........"); 
  Serial.println(); 
  Serial.println("-----------------------------------------"); */
 
}