SERVO CONTROl

Projects General Guidance
1

Hi,
I am trying to control 5 servo motors to specific angles given by a PC via Xbee . A code (encoded servo number and angle ) will be sent from the PC via an Xbee transmitter and will be received using an Xbee receiver. The arduino should convert the received code to angles & servoes and perform the operation. I want the assistance with the code. Any help is welcomed... :slight_smile: :slight_smile:

2

Hey,

Um not so sure about the code but this shield would be perfect for your project. It supports up to 8 servo ports, which is more than enough for you, and has a space to directly connect an xbee receiver to the shield.

hope this helps a little.

3

For only five servos, why bother with a shield?

4

I have got the hardware, I am using the PWM pins of the ARDUINO itself and no other external boards. But i need help in coding the program as I had explained above. I want to serially control multiple servoes, thats all...

5

Don't use PWM to drive R/C servos.
Use the servo library.

But i need help in coding the program as I had explained above.

Well, show us what you've got so far, and then we should be able to help you.

6

Yes , I am using servo library and the PWM pins. Please someone help me on how should I encode the servonumber and angle to send from PC and the code to decode it in the arduino , and rotate the corresponding servos to received angles ???

7

AWOL:
Well, show us what you've got so far, and then we should be able to help you.

// Import the Arduino Servo library
#include <Servo.h> 

// Create a Servo object array for all the 5 servos
Servo servo[6];

// Common servo setup values
int minPulse = 600;   // minimum servo position, us (microseconds)
int maxPulse = 2400;  // maximum servo position, us


int userInput[4];    // User input for servo and position , raw input from serial buffer, 3 bytes
int startbyte=0,start=0,hault=0,endbyte=0;       // start byte (begin reading input),end byte (end reading input),start( started getting data ), hault ( data reception ended ) 
int num=0,pos=0,i;           // num = servo number, pos = angle to take , i for itration

void setup() 
{ 
  // Attach each of the 6 Servo object to a digital PWM pin
  servo[0].attach(3, minPulse, maxPulse);
  servo[1].attach(5, minPulse, maxPulse);
  servo[2].attach(6, minPulse, maxPulse);
  servo[3].attach(9, minPulse, maxPulse);
  servo[4].attach(10, minPulse, maxPulse);
  servo[5].attach(11, minPulse, maxPulse);
 
  // Open the serial connection, 9600 baud
  Serial.begin(9600);
} 

void loop() 
{ 
  // Wait for serial input (min 6 bytes in buffer)
 if (Serial.available() >= 6) 
 {
    startbyte = Serial.read(); // receive the first byte
    if (startbyte == '<')       // check if it is '<' or not
    {
      start=1;                   // if the start bit is correct the code reception starts
      for (i=0;i<4;i++) 
      {
        userInput[i] = Serial.read()-'0';    // reads and stores the 4 values received as numbers in an array
      }
    }
    endbyte= Serial.read();                // receive the 6th bit
    if(endbyte=='>')                    // if it is the ending byte then
    {        
      hault=1;                          // data reception ended
    }
    if ( start==1 && hault==1)          // if data was successfully received
    {
      num = userInput[0];              // identifying the servo from the code
      pos =(userInput[1]*100)+(userInput[2]*10)+userInput[3];    // calculating angle from the next 3 bits of the received code ( 3 bytes to one value conversion )
      Serial.print("Servo No: ");                                // acknowledging the transmitter with the decoded data , angle and servo
      Serial.print(num+1);            
      Serial.print("Angle : "); 
      Serial.print(pos);  
      servo[num].write(pos);                                   // rotate the corresponding dervo to the received angle
      delay(100);                                    // wait till servo reaches that position
      hault=0,start=0;
    }
 }
}

the data sent from the pc will be of the format
<(servonumber)(servo angle in 3 digits)>

8

The sketch looks to be OK, what's the problem?

9

Below is some code I use to test servos I have that might be of interest.

// zoomkat 11-22-10 serial servo (2) test
// for writeMicroseconds, use a value like 1500
// for IDE 0019 and later
// Powering a servo from the arduino usually DOES NOT WORK.
// two servo setup with two servo commands
// send eight character string like 15001500 or 14501550

#include <Servo.h> 
String readString, servo1, servo2;
Servo myservo1;  // create servo object to control a servo 
Servo myservo2;

void setup() {
  Serial.begin(9600);
  myservo1.attach(6);  //the pin for the servo control 
  myservo2.attach(7);
  Serial.println("servo-test-21"); // so I can keep track of what is loaded
}

void loop() {

  while (Serial.available()) {
    delay(1);  
    if (Serial.available() >0) {
      char c = Serial.read();  //gets one byte from serial buffer
      readString += c; //makes the string readString
    } 
  }

  if (readString.length() >0) {
      Serial.println(readString); //see what was received
      
      // expect a string like 07002100 containing the two servo positions      
      servo1 = readString.substring(0, 4); //get the first four characters
      servo2 = readString.substring(4, 8); //get the next four characters 
      
      Serial.println(servo1);  //print to serial monitor to see results
      Serial.println(servo2);
      
      int n1; //declare as number  
      int n2;
      
      char carray1[6]; //magic needed to convert string to a number 
      servo1.toCharArray(carray1, sizeof(carray1));
      n1 = atoi(carray1); 
      
      char carray2[6];
      servo2.toCharArray(carray2, sizeof(carray2));
      n2 = atoi(carray2); 
      
      myservo1.writeMicroseconds(n1); //set servo position 
      myservo2.writeMicroseconds(n2);
    readString="";
  } 
}