Die Beschränkung auf 10 Servos kommt daher, dass die Steuerinmpulse 1 bis 2ms lang sind, und im 20ms-Rhythmus wiederholt werden. Es werden daher die einzelnen Impulse nacheinander ausgegeben, und nach zehn Impulsen mit Maximallänge + Pause ist man automatisch bei dem 20ms.

Die meisten Servos sehen das mit den 20ms aber nicht allzu eng. Du könntest also erst mal versuchen, alle Arrays und Variablen von 10 auf 11 anzupassen. Die Neutrallage der übrigen Servos könnte sich minimal verschieben, aber ansonsten stehen die Chancen gut, dass es klappt.

Code:
/************************************************************************

   SERVO Controller for up to 10 Servos

   controlled by serial line
   default: 2400 Baud 8N1
   
   Processor: ATMEGA 8
   CLOCK: 8MHZ, no prescaler set config bits of Atmega 8 correctly !
   
   Compiler: AVR-GCC


   This code is licensed under the GPL.
   You may modify, redistribute the code .. blabla, you know what I mean ...

   Copyright stochri (c.hab@gmx.net) Nov.2005
   
   Warnungen beiseitigt von uwegw

***************************************************************************/
#include <stdlib.h>
#include <inttypes.h>
#include <avr/io.h>
#include <avr/interrupt.h>

typedef unsigned char byte;

#define SYSCLK 8000000 // timer clock 8Mhz
#define MAXPULSFREQ 500 // 2ms => 500HZ

#define TIMER_MAXPULS SYSCLK/MAXPULSFREQ // Timer1 value for a 2ms Puls

#define MINPULS TIMER_MAXPULS/4  // min pulslength = 0.5ms
#define MAXPULS TIMER_MAXPULS // max pulslength=2ms

// port pin definitions
// you may redefine the pins to suit your application
// tale a look at the interrupt routine and enable the cases for your servo

#define LOW_SERVO0 PORTD&=~(1<<6)
#define HIGH_SERVO0 PORTD|=(1<<6)

#define LOW_SERVO1 PORTB&=~(1<<0)
#define HIGH_SERVO1 PORTB|=(1<<0)

#define LOW_SERVO2 PORTB&=~(1<<1)
#define HIGH_SERVO2 PORTB|=(1<<1)

#define LOW_SERVO3
#define HIGH_SERVO3

#define LOW_SERVO4
#define HIGH_SERVO4

#define LOW_SERVO5
#define HIGH_SERVO5

#define LOW_SERVO6
#define HIGH_SERVO6

#define LOW_SERVO7
#define HIGH_SERVO7

#define LOW_SERVO8
#define HIGH_SERVO8

#define LOW_SERVO9
#define HIGH_SERVO9


uint16_t Pulslength[22]; // !!! // array for all delays

/************************************************************************

   SIGNAL(SIG_OVERFLOW1)
   timer1 interrupt, generates the high and low pulses for each servo

***************************************************************************/
SIGNAL(SIG_OVERFLOW1)
{
   static byte servoindex_half=0;

   switch (servoindex_half)
   {
      case 0: HIGH_SERVO0; break;
      case 1: LOW_SERVO0; break;
      case 2: HIGH_SERVO1; break;
      case 3: LOW_SERVO1; break;
      case 4: HIGH_SERVO2; break;
      case 5: LOW_SERVO2; break;
//      case 6: HIGH_SERVO3; break;
//      case 7: LOW_SERVO3; break;
//      case 8: HIGH_SERVO4; break;
//      case 9: LOW_SERVO4; break;
//      case 10: HIGH_SERVO5; break;
//      case 11: LOW_SERVO5; break;
//      case 12: HIGH_SERVO6; break;
//      case 13: LOW_SERVO6; break;
//      case 14: HIGH_SERVO7; break;
//      case 15: LOW_SERVO7; break;
//      case 16: HIGH_SERVO8; break;
//      case 17: LOW_SERVO8; break;
//      case 18: HIGH_SERVO9; break;
//      case 19: LOW_SERVO9; break;
//		case 20: HIGH_SERVO10; break; // !!!
//      case 21: LOW_SERVO10; break; // !!!
   }

   
   TCNT1 =Pulslength[servoindex_half]; // set time for next interrupt   

    servoindex_half++; // increment timervalue index
   if(servoindex_half==22)servoindex_half=0;   // reset index /!!!
}
/************************************************************************

   void setservo(byte index, byte value)

   Set servo position
   value: 0..255

***************************************************************************/

void setservo(byte index, byte value)
{
   uint16_t wert;

   wert=MINPULS+(MAXPULS-MINPULS)/256*value;
   
   // callculate hightime
   Pulslength[index<<1]=0-wert;
   
   // sume of low and hightime for one servo is 2ms
   Pulslength[(index<<1)+1]=0-(TIMER_MAXPULS-wert);
   
   // 1 Servos give you 1*2ms=22ms total cycle time /!!!
}

/************************************************************************

   void init_servos()
   
   initialize all Servos to the start position
***************************************************************************/
void init_servos(void)
{
   byte n;
   for(n=0;n<11;n++) setservo(n,128); //!!!
}

/************************************************************************

   void init(void)
   initialize the prozessor registers
***************************************************************************/

void init(void)
{
   // prepare RS232
   UCSRA = 0x00;
   UCSRB = 0x00;   
   UCSRC = 0x86; // No Parity | 1 Stop Bit | 8 Data Bit
   UBRRL = 0xCF; // 2400bps @ 8.00MHz
//   UBRRL = 51; // 9600bps @ 8.00MHz
//   UBRRL = 25; // 19200bps @ 8.00MHz

    /* initialize ports */
    DDRB = 0xFF;
    DDRC = 0xFF;
    DDRD = 0xFF;
    PORTB = 0x00;
    PORTC = 0x00;
    PORTD = 0x00;

    // init timer1
   TCNT1 = 0-16000;
   TCCR1A=0;
   TCCR1B=0x01;
    TIMSK |= _BV(TOIE2) | _BV(TOIE1);

    /* allow interrupts */
    sei();
}

/************************************************************************

   serial communication

***************************************************************************/

byte chgetchar(void)
{
   UCSRB = 0x10; // enable receiver
   while(!(UCSRA & 0x80)); // wait for received byte
   return UDR;
}

void chputchar(byte zeichen)
{
   UCSRB = 0x08; // enable transmitter
   UCSRA|=0x40; // clear transmitter flag
   while (!(UCSRA & 0x20)); // wait for empty transmit buffer
   UDR = zeichen;
   while (!(UCSRA & 0x40)); // Wait for transmit complete flac (TXC)
}
void chSerPrint(char *data)
{
   unsigned char i = 0;
   while(data[i]!=0x00) chputchar(data[i++]);
}

/************************************************************************

   main programm

   servo controll by RS232 interface

***************************************************************************/

int main(void)
{
   char c;
   byte n;
   byte servos[10];

   init();
   init_servos();
   
   chSerPrint("\n\r-- Atmega8 servo controller V1.0 --\n\r");
   chSerPrint("Connection OK\n\r");

   while(1)
   {
   
      // get key from terminal
      c=chgetchar();

      if(c=='q') servos[0] += 10;
      if(c=='w') servos[0] -= 10;
      if(c=='a') servos[1] += 10;
      if(c=='s') servos[1] -= 10;
      if(c=='y') servos[2] += 10;
      if(c=='x') servos[2] -= 10;

      // set to default position, if space is pressed
      if(c==' ')
      {
         servos[0] = 128;
         servos[1] = 128;
         servos[2] = 128;
      }

      for(n=0;n<11;n++) setservo(n,servos[n]); //!!!
   }
}
Kompilert einwandfrei, habs allerdings nicht testen können. Die Änderungen habe ich mit //!!! markiert. Könnte sein, dass ich noch was übersehen habe...