Help with Reading and converting serial string

Using Arduino Networking, Protocols, and Devices
#1

Hello,

I’m working on a project using 4D labs, 3.2 uLCD with touch screen where I want to the screen to send serial data something like:

o1234

The o is to tell the arduino its for the on time variable for teh PWM, and the 1234 is umber I want to be palced in the variable as well as limiting the incoming number to 0-9999, right now though I’m just using the terminal window from arduino to try and get the arduino to only read the RX buffer when the o is detected, and to take the individaul ascii characters and combine them into an integer, here’s what I have so far:

void setup() {
Serial.begin(9600); // opens serial port, sets data rate to 9600 bps
}

int str2int(){
int n, x;
int str[4];

n = 4;
while(n–){
if (Serial.available() > 0) //str 0 = 102 and str 3 = 101 str 5 = 100
str[n] = Serial.read();
}

/if (str[3] >= 48 && str[3] <=57){
x = ((str[3]-48) << 10)- ((str[3] -48) * 24);
if (str[2] >= 48 && str[2] <=57){
x = x + (( str[2] - 48) << 7) - ((str[2] - 48) * 28);
if (str[1] >= 48 && str[1] <=57){
x = x + ((( str[1] - 48 ) << 3) + ((str[1] - 48) * 2));/
if (str[3] >= 48 && str[3] <=57){
x = ( str[3]-48 ) ;
}
/* }
}
}*/
return x;
}

void loop() {

if (Serial.available() > 0){
if (Serial.read() == 0x6F)
Serial.println(str2int());
}
}

So far I can get to check for the o, recognize the o, and start reading the actual digits… the problem is I have yet to even be able to get the ascii numbers 48-57 or 0-9, I always get 0, -1, or some random number from 1 - 35652 or even negative numbers.

Any help with getting the arduino to read the digits, and combine them into the equivilant combined integer would be greatly apreciated.

#2

If you just want the total value of the characters

// after getting the 'o'
  n = 4;
  val = 0;
  while(n--) {
    while (Serial.available() == 0); // wait for a character 
      val *= 10;
      val += Serial.read() - '0';
  }

Rob

#3