Arduino-serial: C code to talk to Arduino

186 Replies to “Arduino-serial: C code to talk to Arduino”

1. Pingback: How to use the TSL2561 « Jonathan Thomson's web journal

2. Hi~
   I am trying to cross compile Arduino-serial.c with gcc-mips , I got

   file /usr/bin/arduino-serial
   /usr/bin/arduino-serial: ELF 32-bit MSB executable, MIPS, MIPS32 version 1, dynamically linked (uses shared libs), with unknown capability 0x41000000 = 0xf676e75, not stripped

   but it gives

   root@OpenWrt:/dev# arduino-serial -b 9600 -p /dev/ttyUSB0 -r
   read: p

   all the time instead of

   root@OpenWrt:/dev# cat < /dev/ttyUSB0

   723 Hello world!

   724 Hello world!

   725 Hello world!

   726 Hello world!

   any solutions?

3. Hi
   I’ve alredy solved it it was the autoreset funktion!!
   Thanks for this helpful site and your great code

   Lukas

4. Hi I`m using the same comand as everybody else but it doent work.
   the arduino DOES recive data but doesnt react as it should.
   the funny thing: It works when i leave the arduino serial console open
   But why and how to solve this???

5. It seems like this is somewhat of a common issue and it is my Uno resetting itself each time the serial port is open.

   Below is ome text I found describing the issue, this is based on the Duemilanove but I’m guessing it’s the same for the Uno.

   I read that if you disable DTR on the serial port, then that also solves the issue, is this something that arduino-serial will do?

   Thanks again.

   Phil

   Automatic (Software) Reset

   Rather then requiring a physical press of the reset button before an upload, the Arduino Duemilanove is designed in a way that allows it to be reset by software running on a connected computer. One of the hardware flow control lines (DTR) of the FT232RL is connected to the reset line of the ATmega168 or ATmega328 via a 100 nanofarad capacitor. When this line is asserted (taken low), the reset line drops long enough to reset the chip. The Arduino software uses this capability to allow you to upload code by simply pressing the upload button in the Arduino environment. This means that the bootloader can have a shorter timeout, as the lowering of DTR can be well-coordinated with the start of the upload.

   This setup has other implications. When the Duemilanove is connected to either a computer running Mac OS X or Linux, it resets each time a connection is made to it from software (via USB). For the following half-second or so, the bootloader is running on the Duemilanove. While it is programmed to ignore malformed data (i.e. anything besides an upload of new code), it will intercept the first few bytes of data sent to the board after a connection is opened. If a sketch running on the board receives one-time configuration or other data when it first starts, make sure that the software with which it communicates waits a second after opening the connection and before sending this data.

   The Duemilanove contains a trace that can be cut to disable the auto-reset. The pads on either side of the trace can be soldered together to re-enable it. It’s labeled “RESET-EN”. You may also be able to disable the auto-reset by connecting a 110 ohm resistor from 5V to the reset line; see this forum thread for details.

6. I’m trying to make my Mac to comunicate with arduino thru chars. I only get your app to work when the Arduino IDE’s serial monitor is already opened. I’m on a Intel Mac, Lion OS X and running arduino 1.0 software. The hardware is a Seeeduino. Thank you for your effort!

7. Hi Phil,

   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.

8. After some experimentation I have it somewhat working.

   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

   char val; // variable to store the data from the serial port
   char buffer[5]; // string array

   void setup() {
   Serial.begin(9600); // connect to the serial port
   }

   void loop () {
   val = Serial.read(); // read the serial port

   if (val > -1) { // check for the start of valid data

   buffer[0] = val; // put the first charcter into the buffer

   for (int i=1; i < 4; i++) { // read 4 more characters

   buffer[i] = Serial.read();
   } // end loop

   Serial.println(buffer);
   } // end if
   }

9. Hi, this is great and seems to work well for me so far.

   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

10. Hi

    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

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12. Hello,

    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.

13. How can i send a int to the board?

    Cheers, Henry

14. I’m trying to send a command to the arduino and get a response but I can’t seem to get it to work:

    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.

15. [SOLVED] I’ve spent over a month trying to have a good communication between linux (Debian Squeeze) and ARDUINO using C programming. I tried every possible configuration with termios.h. My problem was that linux seems to communicate twice at the beginning of the connection with ARDUINO, confusing all the following dialogue. I don’t now why it happens, but finally I’ve found a solution to solve it.

    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.

16. Finally got it resolved, with a lot of help from a friend. We’re using an AppleScript to telnet to ser2sock
    to the Arduino, attached to a remote machine.

    Many thanks,

    Carl

17. Hi Carl,
    Can you post your Arduino sketch so I can try it myself?

18. I got the Arduino to respond to this input from Terminal: arduino-serial -b 9600 -p /dev/tty.usbmodemb21 -d 2000 -s b
    but the Arduino LED just flashes 3 times very quickly, regardless of what I have programmed into it’s sketch.

    Any idea what may be going on?

    Thanks,

    Carl

19. I got the Arduino to respond to this Terminal input: arduino-serial -b 9600 -p /dev/tty.usbmodemb21 -s a
    but the LED just does 3 quick flashes, not what was programmed for the LED to do in the sketch.

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

    Any ideas?

    Carl

20. Oh! It sounds like you don’t yet have the “arduino-serial” program compiled yet.
    Did you do the steps at the top of this post? (e.g. “gcc -o arduino-serial arduino-serial.c”)
    It is likely you do not have the Mac OS X developer tools installed (it’s an optional install).
    If that’s the case, here’s a compiled version of arduino-serial:
    http://todbot.com/arduino/host/arduino-serial/arduino-serial-macosx.zip