mwheels / libcssl

This is a short description of Columbo Simple Serial Library.
http://cssl.sourceforge.net

1) Installing libcssl

2) Compiling and linking your applications against libcssl

3) Using libcssl

   - Event driven mode
     a) callback function
     b) starting
     c) openig ports
     d) setting flow cotrol
     e) sending data
     f) receiving data
     g) changing port setup
     h) errors
     i) finishing

   - Blocking mode
     a) notes
     b) setting the timeout value
     c) receiving data

===========================================================
1) Installing libcssl
Read INSTALL file

===========================================================
2) Compiling and linking your applications against libcssl

First, in your C files you should include libcssl.h:

#include <cssl.h>

To compile and link your program against libcssl do for
example as follows:

$ gcc -Wall -O -o my_program my_program.c -lcssl

You can use pkg-config too:

$ -Wall -O -o my_program `pkg-config --cflags --libs libcssl` my_program.c
===========================================================
3) Using libcssl

   - Event driven mode
      a) write a callback function, for example:

         void callback_function(int id, unit8_t *buf, int buflen)
         {
              int i;
              for(i=0;i<buflen;i++) {
                   putchar(buf[i]);
              }
              fflush(stdout);
         }

         The callback function is executed when a data arrives
         on your serial port. It gets three variables:
         int id - the ID of the port. You set it while port opening.
                  It can be useful for you to identify the port
                  when you use the callback_function for more then
                  one serial port.
         uint8_t *buf - incoming data
         int buflen - incoming data length.

         The example callback you see just copies the data to stdout.

      b) start libcssl:

         cssl_start()


      c) open a port:

         cssl_t *serial;
         serial=cssl_open(path,
                          callback_function,
                          id,
                          baud,
                          bits,
                          parity,
                          stopbits);

         cssl_open creates new cssl_t structure, opens the port,
         and sets it up. It sets flow control to 'none'.

            path - path to the port special file, for example: "/dev/ttyS0"
            callback_function - your callback function,
            id - port id, you could nedd it only when you use more then
                 one port
            baud - baudrate you want set for the port, integer:
                   150,300,600,1200,2400,4800,9600,19200,38400,57600,115200
            parity - parity bit:
                   0-none, 1-odd, 2-even
            bits - bits per character: 7 or 8
            stopbits - as the name says: 1 or 2
           
      d) cssl_open and cssl_setup always set up flow control to 'none'.
         To change this use:

            cssl_setflowcontrol(cssl_t *serial, int rtscts, int xonxoff);

          rtscts - give 1 when you want hardware (RTS/CTS) flow control,
                   0 if you don't want it.
          xonxoff - give 1 when you want software (XON/XOFF) flow control,
                   0 if you don't want it.

         Of course you can use both.

      e) Sending data
         ---
         cssl_putchar(cssl_t *serial, char c);

         It sends one char to the serial port, example:
         cssl_putchar(serial,'A');
         ---
         cssl_putstring(cssl_t *serial, char *str);

         It sends null terminated string to the port, example:
         cssl_putstring(serial,"Hello, world!");
         ---
         cssl_putdata(cssl_t *serial, uint8_t *buf, int len);

         It sends a data buffer to the port. Example:
         uint8_t *buffer={1,2,3,4,5,6,7,8};
         (...)
         cssl_putdata(serial,buffer,8);
         ---
         cssl_drain(cssl_t *serial);

         It waits until all data sent to the port has been transmited.

      f) Receiving data.
         You do it via callback function.

      g) Changing port setup.

         cssl_setup(serial
                    baud,
                    bits,
                    parity,
                    stopbits);

         Look at cssl_open.

      h) Errors
         After every operation libcssl sets the error code.
         You can get it with:

         int cssl_geterror();

         Or you can get the status massage with:

         char *cssl_geterrormsg();

         If everything is OK, the error code should be CSSL_OK.

      i) Finishig

         cssl_close(cssl_t *serial)

         It closes the port and frees the port's resources.

         cssl_stop()

         It closes all the ports, and stops receiving of signals

   - Blocking mode
     This feature is not tested.

     a) To use the port in blocking mode (your machine will wait for
        characters) just set callback_function to NULL. Everething
        else will work as in event driven mode.

     b) Setting the port timeout:

        cssl_set_timeout(cssl_t *serial, int timeout);

        It sets the timeout for the port. The unit is decisecond (hundred
        of miliseconds)

     c) Receiving data:

        int cssl_getchar(cssl_t *serial);

        It gets a character from the port, and returns it or -1,
        when an error occured (for example timeout).

        int cssl_getdata(cssl_t *serial, uint8_t *buffer, int buflen)

        It reads data from the port, places it into the given buffer.
        It returns when error occurs or when it has read buflen bytes.
        The function returns number of read data.


If you didn't understand everything then read test.c, cssl.c
and cssl.h files.

Marcin Siennicki
[email protected]