Controlling Robots Through Serial

Question

I recently have been working on a little project. Unfortunately, I've ran into a bit of a road block with controlling servos using serial commands. The servos do appear to move when i put in any character into serial, but only a little. When i type in say, 90 characters of random gibberish, both servos connected to my arduino move several degrees. Here's my code:

#include <Servo.h>
Servo ULF; // Upper left front servo
Servo LLF; // Lower left front servo
byte index = 0;
int commandnum=1;
int steps = 0; // position of LLF servo
int partnum = 0; // unused for now
String command = ""; // the command we're building
void setup()
{
  LLF.attach(0);
  ULF.attach(1);
  Serial.begin(9600);
}

void loop()
{
  while(Serial.available() > 0) { // while there are more than zero bytes to read
      char in = Serial.read();
      if(in=='!') {
             //! is escape character
       commandnum++;
       partnum = 0;
       Serial.println("New Command. Command #: "+commandnum);
        break;
      }
      command+=in;
      if(in == ' ') {
        partnum++;
        //if we have a space, there's a new section to the command
      }
      if(command == "LLF") {
        Serial.read(); //skip a space

        Serial.println("Lower Left Foot Selected.");
        int angle = Serial.parseInt(); // find the angle we want
        Serial.println("ANGLE: "+String(angle));

        for(int pos = 0; pos < angle; pos++) // for loop through positions to reach goal
        {                                  
           LLF.write(pos); // write servo position
           delay(15);
        } 
        for(int pos = angle; pos > 0; pos--) // for loop through positions to reach goal
        {                                  
           LLF.write(pos); // write servo position
           delay(15);
        } 
      }
   }
}

Any help would be much appreciated.

EDIT: Another note, nothing is printed in the serial monitor.

Also, these are micro towerpro rc servos.

Answer 1

I rewrote your program a bit. Not tested since I have no servos.

#include <Servo.h>
Servo ULF; // Upper left front servo
Servo LLF; // Lower left front servo
byte index = 0;
int commandnum=1;
int steps = 0; // position of LLF servo
int partnum = 0; // unused for now
String command = ""; // the command we're building
char in;                // character to read
int angle;              // desired angle

void setup()
{
  LLF.attach(0);
  ULF.attach(1);
  Serial.begin(9600);
}

void loop()
{
    // define a protocol for commands, maybe like this:
    // [XXX<d>] where XXX is command and <d> is the angle,
    // the brackets [] indicates start and stop of a "packet" ( the command ).
    // Example: [LLF120], [LLF035], [LLF005]. I am here assuming a 3-digit
    // value for angle.

    // You also need to reset the variables that holds the command data
    // when the command has been executed so that they are ready for the next command.
    // and to use parseInt() you must ensure that the serial buffer has all the 
    // digits that you sent.

  if(Serial.available() > 0) { // if there are more than zero bytes to read
      in = Serial.read();
      if(in == '[') // start of packet, now read command
      {
        command = "";

        // get command, 3 chars
        while(command.length() < 3)
        {
            if(Serial.available() > 0)
                command += Serial.read();

            delay(10);  
        }

        // get angle    
        while(Serial.available() < 3) 
        {               
            delay(10);  
        }

        angle = Serial.parseInt(); // find the angle we want

        // flush buffer, all info received
        Serial.flush();
      }   

      if(command == "LLF") {

        Serial.println("Lower Left Foot Selected.");

        Serial.println("ANGLE: "+String(angle));

        for(int pos = 0; pos < angle; pos++) // for loop through positions to reach goal
        {                                  
           LLF.write(pos); // write servo position
           delay(15);
        } 
        for(int pos = angle; pos > 0; pos--) // for loop through positions to reach goal
        {                                  
           LLF.write(pos); // write servo position
           delay(15);
        } 
      }
   }
}

Answer 2

According to the Arduino reference for Servo.attach( ), you should be using pins 9 and 10, not 0 and 1.

Note that in Arduino 0016 and earlier, the Servo library supports only servos on only two pins: 9 and 10.

Verify that you are setting the proper pin number in code. Specifically, look at these lines in your originally-posted code:

void setup()
{
  LLF.attach(0);
  ULF.attach(1);

Answer 3

Does a simple serial sketch work? If yes, then try using this code: What this does is it takes two bytes simultaneously, the first indicating the pin number and the second the analog value, and then sets the pin mode. I am sure you can modify it for your own needs. This is the code I use for my robot. Hope this helps. (sorry, arduino indentation is weird)

int pin = -999;
int val = -999;
int count = 0;

void setup()
{
    Serial.begin(9600);
}

void loop()
{

}

void serialEvent()
{
    //As soon as a byte arrives
    while(Serial.available())
    {
        //Read it
       int data = Serial.read();
       if (count == 0)
       {
           pin = data;
       }
       else if(count == 1)
       {
           val = data;
       }
       count = count + 1;

       if (count == 2)
       {
          //Time for reset
          count = 0;

          //execute
          analogWrite(pin,val);

       }
    } 

}