The problem is the Arduino is operating “too fast” for the serial input data stream so that “Serial.read()” is returning -1 when you do your buffer[i] = Serial.read();. You need to check for -1 every time you do “Serial.read()“, unless you are absolutely sure Serial has all the data you need.

One way to do this is to wait for the data at every character, like:

  for( int i=1; i< 4; i++) {
    while( !Serial.available() ) ; // wait for data
    buffer[i] = Serial.read();
  }

But that technique will hang waiting for data if none comes.

If you know exactly how many bytes are being sent, though, the receiving gets easier. For your "hello" example, it can be:

void loop() {
  if( Serial.available >= 5 ) {  // wait for at least 5 bytes
    for( int i=0; i<5; i++) {
      buffer[i] = Serial.read();
    }
   Serial.println(buffer);
  }
}

I talk about this in Arduino serial protocol design patterns. Receiving and parsing data on the Arduino is currently a bit messy if the data isn’t a fixed length in size. This will get better soon, as an Arduino update is coming that will have ways of receiving until a newline or other arbitrary character.

However, I was expecting my final string to be “hello” but right now it looks like this.

hÿÿÿ
eÿÿÿ
lÿÿÿ
lÿÿÿ
oÿÿÿ

I’m guessing that there is some kind of carriage return or something being sent.

Here is my code.

Any ideas?

Thanks.

Phil

I am wondering what the best way to recompile the data I receive into a string.

Basically I am using arduino-serial to send text that I want to display on a 16×2 LCD screen hooked up to my arduino.

If I use “/Applications/arduino-serial -b 9600 -p /dev/tty.usbmodem1d21 -s hello”

My arduino returns:

104
101
108
108
111

Which is the ascii characters for each of the letters.

I’m thinking I need some form of array that waits for the first character that is not -1 then stores each character until the next -1

I am pretty new to Arduino and this seems a little tricky.

Any advice?

Thanks.

Phil

I am trying to use:-
laptop% ./arduino-serial -b 9600 -p /dev/ttyUSB0 -s get -r

I don’t get back what I expect. Is there an Arduino sketch I can download that is known to work with arduino-serial used in this way?

Regards

I’m starting an Arduino Project in wich i need to communicate several Arduino boards with one PC via serial port. I know almost nothing about working with serial ports so I’m first learning about it.
Your code is being really useful for me. Now I’m starting to write a bit of code on my own but using yours as a refference for the “setting the serial connection” part since I’m still getting familiar with this.

I’ve seen that yor work is under a CC license but I’m not sure about the specifications. Do you allow derived works? Is it OK for you if I publish something of my code based on yours giving recognition to you?

Thanks,

Sakul.

Cheers, Henry

command:
./arduino-serial -b 9600 -p /dev/ttyUSB0 -d 2000 -s foo -r

response:
read: foo

the response is whatever I tried to send the arduino, my sketch sends different output depending on the command sent.

So, this is the C code to initialize serial connection with ARDUINO using termios.h. If you don’t know how the following functions work, I suggest this link: http://pubs.opengroup.org/onlinepubs/7908799/xsh/termios.h.htmlSo.
—- Beginning of C code —–

#include    /* File control definitions */
#include    /* Error number definitions */
#include  /*linux serial library*/
#define DEVICE_ADDR "/dev/ttyACM0"

int main()
{
 struct termios options;
 fd = open(DEVICE_ADDR, O_RDWR | O_NOCTTY | O_NDELAY);
 if (fd<0) perror("open_port: Unable to open /dev/ttyACM0 - ");

 options.c_cflag=6322; //6322 is for BOUDRATE 115200, if you want 9600 use 2237 instead
 options.c_lflag=0;
 options.c_iflag=0;
 options.c_oflag=0;

 tcsetattr(fd, TCSANOW, &options);

 //the following two lines is the strange thing that makes the whole thing work
 sleep(1); //Sleep time works only from 1 to 2 (2 not included)
 tcflush(fd, TCIFLUSH);

— end of C code —

This is all, from now on you can add your own code to read and write with ARDUINO, using C read and write functions.
Have a good programming day.

Many thanks,

Carl

Any idea what may be going on?

Thanks,

Carl

In fact it just flashes the LED regardless of what I send it or what is in the sketch to do.

Any ideas?

Carl

Carl