reading serial data packet

Forum 2005-2010 (read only) Software Syntax & Programs
1

Hello
I'm Wim and I'm from Holland.
I started learning Arduino a couple of weeks ago, and its going quite well.
But now I need some help.

Problem is I want to read a serial data packet from a sim program.
This is wat it sends:
X~a01~Y~a02~
Where X and Y are axis and send as ascii, no problem reading that.
But ~a01~ and ~a02~ are variables from 0-255
I can read this as well, except when setting my baud speed higher or the refresh time of the program under 2ms.
The program does not support hardware handshaking.

I want to know what the most reliable way of reading the data-packet is.

My code so far.

#include <Servo.h>
#include <LiquidCrystal.h>
int servoPanPin = 11;     // Control pin for servo motor
int servoTiltPin = 12;     // Control pin for servo motor

int pos = 0;
int newpos =0;                 // position
int pos2 = 0;
char axis;

Servo panServo;
Servo tiltServo;
LiquidCrystal lcd(9, 8, 7, 6, 5, 4);
void setup()
{
  Serial.begin(9600);
    lcd.begin(16, 2);
  panServo.attach(servoPanPin);  
  tiltServo.attach(servoTiltPin);  
}


void loop()
{
  if ( Serial.available())
  {
    char ch = Serial.read();
    if(ch >= '0' && ch <= '9')      
    {        // is ch a number?  
       pos = pos * 10 + ch - '0';           // yes, accumulate the value
         newpos = map(pos,0,255,0,180);
    }
    else if(ch == 'X' || ch == 'x')  // pan
    {
      panServo.write(newpos);          
        Update_lcd('x',newpos);
      pos = 0;
    }
    else if(ch == 'Y' || ch == 'y')  // tilt
    {
      tiltServo.write(newpos);        
        Update_lcd('y',newpos);
      pos = 0;
    } 
   
    else if(ch == 'C' || ch == 'c')  // clear
    {
      Update_lcd('c',newpos);
    }
    
     else if(ch == 't' || ch == 'T')  // clear
    {
      set_servo();
    }
  }
}

void Update_lcd(char axis, int pos2)

{
  if(axis == 'x')
  {
    lcd.print("X:");
    lcd.print(pos2);
    lcd.print(" ");
  }
  
  else if(axis == 'y')
  {
    lcd.print("Y:");
    lcd.print(pos2);
    lcd.print(" ");
  }
   else if(axis == 'c')
  {
    lcd.clear();
  }
}
 
void set_servo()
{
  tiltServo.write(90);
  panServo.write(90);
 
}

Excuse me for the way I program, I'm still learning. :wink:

Thanks in advance. :wink:

2

On each pass through loop, you read at most one character from the serial port. If there is more than one available, they should all be read and processed.

Change the if(Serial.available() statement to while(Serial.available()) to do this.

3

thanks a lot.

So the code to read the values is fine as it is?

4

The only thing I'd change would be to move the call to the map function out of the block that reads the value into the block that uses the value. map uses integer division and multiplication to compute the new value, which is not what the Arduino does well. Minimizing when these functions are performed will result in an overall increase in performance/response rate.