Arduino, two stepper motors with serial input driven like 360º servos. Processing interface.

stepperDualServo.pde

//Code for Arduino
//

#include <Stepper.h>

//may need to change this depending on manufacturing variences..
const int stepsPerRevolution = 2050;

//placeholders to keep track of both motors' positions
unsigned int currentPos1 = 0;
unsigned int currentPos2 = 0;

//placeholder for numerical value received over serial
int value;

//stepper motor objects
Stepper stepper1(stepsPerRevolution, 2, 3, 4, 5);
Stepper stepper2(stepsPerRevolution, 10, 11, 12, 13);

void setup() {
  //max speed for motor (28BYJ-48)
  stepper1.setSpeed(5);
  stepper2.setSpeed(5);
  //start serial comms
  Serial.begin(9600);
}

void loop() {
  int i; 
  
    if(Serial.available()){
    i = Serial.read();
    if ((i>='0') && (i<='9')) {
      value = 10*value + i - '0';
    } else {
      //sending ###q or ###w over serial will reset where the arduino
      //currently thinks the motor is - e.g. 0q will reset m1 to 0 degrees
      if (i=='q') {
        Serial.print("Setting current pos of m1 to ");
        Serial.println(value);
        currentPos1 = value;
      }
      if (i=='w') {
        Serial.print("Setting current pos of m2 to ");
        Serial.println(value);
        currentPos2 = value;
      }
      //main input commands - 90l will move m1 to 90 degees
      if(i=='l'){
        moveToAngle(value, currentPos1, stepper1);
        Serial.print('k');
      }
      if(i=='r'){
        moveToAngle(value, currentPos2, stepper2);
        Serial.print('k');
      }      
       
      value = 0;
    }
  
  }
}


void moveToAngle( int value, unsigned int &currentPos, Stepper &motor){
  //this function calculates the difference in angles
  //and moves the motor accordingly
  int moveValue = 0;
  if(value < currentPos){
   moveValue = (360-currentPos)+value;
  }
  if(value > currentPos){
   moveValue = value-currentPos; 
  }
  float factor = (float)stepsPerRevolution/360;
  float stepsToMove = factor*moveValue;       
  motor.step((int)stepsToMove);  
  currentPos = value; 
}

stepperSemaphore.pde

//Code for Processing
// 

import processing.serial.*;
Serial arduino;

String typedText = "abc";
 
PFont font;
 
void setup() {
  size(700, 200);
  arduino = new Serial(this, Serial.list()[5], 9600);
  font = createFont("Helvetica", 18);  
}
 
void draw() {
  background(255);
  fill(255,0,0);
  textFont(font,18);
  text(typedText+(frameCount/10 % 2 == 0 ? "_" : ""), 35, 45);
}
 
void keyReleased() {
  if (key != CODED) {
    switch(key) {
    case BACKSPACE:
      typedText = typedText.substring(0,max(0,typedText.length()-1));
      break;
    case TAB:
      typedText += "    ";
      break;
    case ENTER:
    case RETURN:
      processText(typedText);
      typedText = "";
      break;
    case ESC:
    case DELETE:
      break;
    default:
      typedText += key;
    }
  }
}

void processText(String t){
    //loop through input string
    char[] allChars = new char[t.length()];
    for (int i = 0; i < t.length(); i++) {
      allChars[i] = t.charAt(i);
      int[] values = getValue(allChars[i]);      
      sendChar(values[0], 'l');
      sendChar(values[1], 'r');
      println("sleep");
      delay(4000);
      println("nosleep");
    } 
}


int[] getValue(char letter){
  //define a placeholder for our values
  int[] selectedLetter = new int[2];
  
  //match up the input letter to a set of angles
  switch(letter){
    case 'a': 
      selectedLetter[0] = 120;
      selectedLetter[1] = 80;
      break; 
    case 'b': 
      selectedLetter[0] = 40;
      selectedLetter[1] = 130;
      break;
    case 'c': 
      selectedLetter[0] = 280;
      selectedLetter[1] = 340;
      break;
    case 'd': 
      selectedLetter[0] = 40;
      selectedLetter[1] = 90;
      break;      
    //and so on and so on...
    default: 
      selectedLetter[0] = 0;
      selectedLetter[1] = 0;
  }  
  //pass back the matched up letter
  return selectedLetter;
} 

void sendChar(int deg, char motor){
      println("senChar routine");
      println(deg+""+motor);
      arduino.write(deg+""+motor);
      int co = 0;
      while (arduino.available() == 0){
        //do nothing whilst we wait for a response
        if(co == 0){
          println("waiting for arduino");
        }
        co++;
      }
      
      while (arduino.available() > 0) {
        //there is an incoming byte in the serial buffer
        //this will be a confirmation that the motor has 
        //reached its position
        int inByte = arduino.read();
      } 
}