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June 1, 2016 23:04
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linux serial port writing/reading
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#include <stdio.h> | |
#include <errno.h> | |
#include <termios.h> | |
#include <unistd.h> | |
#include <string.h> | |
/* source : http://stackoverflow.com/a/6947758 */ | |
int set_interface_attribs (int fd, int speed, int parity) { | |
struct termios tty; | |
memset (&tty, 0, sizeof tty); | |
if (tcgetattr (fd, &tty) != 0) { | |
perror ("error from tcgetattr"); | |
return -1; | |
} | |
cfsetospeed (&tty, speed); | |
cfsetispeed (&tty, speed); | |
tty.c_cflag = (tty.c_cflag & ~CSIZE) | CS8; // 8-bit chars | |
// disable IGNBRK for mismatched speed tests; otherwise receive break | |
// as \000 chars | |
tty.c_iflag &= ~IGNBRK; // disable break processing | |
tty.c_lflag = 0; // no signaling chars, no echo, | |
// no canonical processing | |
tty.c_oflag = 0; // no remapping, no delays | |
tty.c_cc[VMIN] = 0; // read doesn't block | |
tty.c_cc[VTIME] = 5; // 0.5 seconds read timeout | |
tty.c_iflag &= ~(IXON | IXOFF | IXANY); // shut off xon/xoff ctrl | |
tty.c_cflag |= (CLOCAL | CREAD);// ignore modem controls, | |
// enable reading | |
tty.c_cflag &= ~(PARENB | PARODD); // shut off parity | |
tty.c_cflag |= parity; | |
tty.c_cflag &= ~CSTOPB; | |
tty.c_cflag &= ~CRTSCTS; | |
if (tcsetattr (fd, TCSANOW, &tty) != 0) { | |
perror ("error from tcsetattr"); | |
return -1; | |
} | |
return 0; | |
} | |
void set_blocking (int fd, int should_block) { | |
struct termios tty; | |
memset (&tty, 0, sizeof tty); | |
if (tcgetattr (fd, &tty) != 0) | |
{ | |
perror ("error from tggetattr"); | |
return; | |
} | |
tty.c_cc[VMIN] = should_block ? 1 : 0; | |
tty.c_cc[VTIME] = 5; // 0.5 seconds read timeout | |
if (tcsetattr (fd, TCSANOW, &tty) != 0) | |
perror ("error setting term attributes"); | |
} | |
/** usage : | |
... | |
char *portname = "/dev/ttyUSB1" | |
... | |
int fd = open (portname, O_RDWR | O_NOCTTY | O_SYNC); | |
if (fd < 0) | |
{ | |
perror ("error %d opening %s: %s", errno, portname, strerror (errno)); | |
return; | |
} | |
set_interface_attribs (fd, B115200, 0); // set speed to 115,200 bps, 8n1 (no parity) | |
set_blocking (fd, 0); // set no blocking | |
write (fd, "hello!\n", 7); // send 7 character greeting | |
usleep ((7 + 25) * 100); // sleep enough to transmit the 7 plus | |
// receive 25: approx 100 uS per char transmit | |
char buf [100]; | |
int n = read (fd, buf, sizeof buf); // read up to 100 characters if ready to read | |
*/ |
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