can't convert char into int and than print it

Projects Interfacing w/ Software on the Computer
1

I am using pyserial to send string value to arduino like this:

#!/usr/bin/python
import serial
import syslog
import time

#The following line is for serial over GPIO
port = '/dev/ttyACM0' # note I'm using Mac OS-X


ard = serial.Serial(port,9600,timeout=5)
time.sleep(2) # wait for Arduino

i = 0

while (i < 4):
    # Serial write section
    ard.flush()
    data = "123"
    ard.write(str(data))
    time.sleep(1) # I shortened this to match the new value in your Arduino code

    # Serial read section
    msg = ard.read(ard.inWaiting()) # read all characters in buffer
    print ("Message from arduino: ")
    print msg
    i = i + 1
else:
    print "Exiting"
exit()

But when i run it, i donot get the correct value. I wanted to get the same value as i've sent. My arduino code is:

// Serial test script
#include <Servo.h>

Servo joint1;
Servo joint2;
Servo joint3;

int setPoint = 55;
String readString;
char c;

void setup()
{
  Serial.begin(9600);  // initialize serial communications at 9600 bps
  joint1.attach(3);
  joint2.attach(5);
  joint3.attach(6);
}

void loop()
{
  while(!Serial.available()) {}
  // serial read section
  while (Serial.available())
  {
    delay(30);
    if (Serial.available() >0)
    {
      c = Serial.read();  //gets one byte from serial buffer
      readString += c; //makes the string readString
    }
  }

  if (readString.length() > 0)
  {
    Serial.print("Arduino received: ");  
    Serial.println(readString);
    int pos1 = atoi(readString[0])*100+atoi(readString[1])*10+atoi(readString[2]);
    joint1.write(pos1);
    Serial.println(pos1);
    readString = "";
  }

  delay(30);
}

Here right now i'm only using one servo command. What i want to do it, i want to first send a string of length 9 like "123456789", than in arduino convert that string into 3 parts as pos1 = 123, pos2 = 456, pos3 = 789. But i'm not able to do it.

2

You do not have a robust program for receiving the data. Have a look at the examples in Serial Input Basics - simple reliable ways to receive data.

And this Python - Arduino demo may also be of interest.

Ensure that your Python program keeps the serial port open until it is completely finished with the Arduino. Closing and opening the serial port causes most Arduinos to reset.

...R

3

thank u, and wow, that link u showed me was amazing. just what i wanted.