DD2-monitor/serial/serial.c

#include <stdio.h>
#include  <stdlib.h>
#include  <sys/select.h>
#include <unistd.h>			//Used for UART
#include <fcntl.h>			//Used for UART
#include <termios.h>		//Used for UART

#include  "serial.h"

/* -------------------------------------------------------------------- */
static int baudrate2const(int bauds)
{
int	br;

switch (bauds)
	{
	case 1200:	br = B1200;		break;
	case 2400:	br = B2400;		break;
	case 4800:	br = B4800;		break;
	case 9600:	br = B9600;		break;
	case 19200:	br = B19200;		break;
	case 38400:	br = B38400;		break;
	case 57600:	br = B57600;		break;
	case 115200:	br = B115200;		break;
	default:
		fprintf(stderr, "baudrate %d invalide\n", bauds);
		exit(1);	
		break;
	}
return br;
}
/* -------------------------------------------------------------------- */

int prepare_UART(char *port, int baudrate)
{
int		uart0 = -1;
int		baudbits;
struct termios	options;

#if DEBUG_LEVEL
fprintf(stderr, "%s ( %s %d )\n", __func__, port, baudrate);
#endif
// OPEN THE UART
// The flags (defined in fcntl.h):
//	Access modes (use 1 of these):
//		O_RDONLY - Open for reading only.
//		O_RDWR - Open for reading and writing.
//		O_WRONLY - Open for writing only.
//
//	O_NDELAY / O_NONBLOCK (same function) - Enables nonblocking mode.
// When set read requests on the file can return immediately with a
// failure status
// if there is no input immediately available (instead of blocking).
// Likewise, write requests can also return
// immediately with a failure status if the output can't be written
// immediately.
//
// O_NOCTTY - When set and path identifies a terminal device, open()
// shall not cause the terminal device to become the controlling terminal
// for the process.

uart0 = open(port, O_RDWR | O_NOCTTY);
if (uart0== -1)
	{
	perror("unable to open uart ");
	return -1;
	}
	
// CONFIGURE THE UART
// The flags defined in /usr/include/termios.h -
// see http://pubs.opengroup.org/onlinepubs/007908799/xsh/termios.h.html
//	Baud rate:- B1200, B2400, B4800, B9600, B19200, B38400, B57600,
//	B115200, B230400, B460800, B500000, B576000, B921600, B1000000,
//	B1152000, B1500000, B2000000, B2500000, B3000000, B3500000, B4000000
//	CSIZE:- CS5, CS6, CS7, CS8
//	CLOCAL - Ignore modem status lines
//	CREAD - Enable receiver
//	IGNPAR = Ignore characters with parity errors
//	ICRNL - Map CR to NL on input (Use for ASCII comms where you want
//	to auto correct end of line characters - don't use for bianry comms!)
//	PARENB - Parity enable
//	PARODD - Odd parity (else even)


baudbits = baudrate2const(baudrate);
#if DEBUG_LEVEL
fprintf(stderr, "%d -> 0x%04x\n", baudrate, baudbits);
#endif
tcgetattr(uart0, &options);
options.c_cflag = baudbits | CS8 | CLOCAL | CREAD;	//<Set baud rate
options.c_iflag = IGNPAR;
options.c_oflag = 0;
options.c_lflag = 0;
tcflush(uart0, TCIFLUSH);
tcsetattr(uart0, TCSANOW, &options);

return uart0;
}
/* -------------------------------------------------------------------- */
/*
 *	this function have NO timeout !
 */
int getbyte(int fd)
{
unsigned char   byte;
int             foo;

foo = read(fd, &byte, 1);
if (1 != foo)
        {
        perror("read a byte");
        return -1;
        }
return (int)byte;
}

/* -------------------------------------------------------------------- */
/* timeout is in milliseconds */
int getbyte_to (int fd, int to_ms)
{
unsigned char   byte;
struct timeval	timeout;
fd_set 		rfds;
int		retval;

timeout.tv_sec  = to_ms / 1000;
timeout.tv_usec = (to_ms % 1000) * 1000;

#if DEBUG_LEVEL
fprintf(stderr, "timeout %6d is %4ld %6ld\n", to_ms,
				timeout.tv_sec, timeout.tv_usec);
#endif

FD_ZERO   (&rfds);
FD_SET    (fd, &rfds);

retval = select(1, &rfds, NULL, NULL, &timeout);

#if DEBUG_LEVEL
fprintf(stderr, "%s : select -> %d\n", __func__, retval);
#endif

retval = retval < 0 ? -1 : retval;

switch (retval) {

	case -1:
		fprintf(stderr, "omg ?\n");
		byte = -1;
		break;

	case 0:
		fprintf(stderr, "timeout\n");
		byte = -99;
		break;

	default:
		if (retval==fd) {
			read(fd, &byte, 1);
			fprintf(stderr, "got 0x%02x\n", byte);
			}
		else	{
			fprintf(stderr, "%d bad fd ?\n", retval);
			byte = -3;
			}
		break;
	}

return byte;
}
/* -------------------------------------------------------------------- */