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serial port write in c
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| #include <stdio.h> /* Standard input/output definitions */ | |
| #include <string.h> /* String function definitions */ | |
| #include <unistd.h> /* UNIX standard function definitions */ | |
| #include <fcntl.h> /* File control definitions */ | |
| #include <errno.h> /* Error number definitions */ | |
| #include <termios.h> /* POSIX terminal control definitions */ | |
| #include <stdlib.h> /* Int to string conversion */ | |
| int open_port(char *port) | |
| { | |
| int fd; | |
| fd = open(port, O_RDWR | O_NOCTTY | O_NDELAY); | |
| if(fd == -1){ | |
| //could not open port | |
| perror("open_port: unable to open port"); | |
| } else { | |
| fcntl(fd, F_SETFL, 0); | |
| } | |
| return (fd); | |
| } | |
| int write_data(int fd, char *data, int bytes) | |
| { | |
| int n; | |
| n = write(fd, data, bytes); | |
| if(n < 0){ | |
| perror("write() of byte failed!\n"); | |
| } | |
| return n; | |
| } | |
| void close_port(int fd) | |
| { | |
| close(fd); | |
| return; | |
| } |
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| /* open the port specified by port. return file handle */ | |
| int open_port(char *port); | |
| /* write data of size bytes to fd. return number of bytes written */ | |
| int write_data(int fd, char* data, int bytes); | |
| /* close port specified by fd */ | |
| void close_port(int fd); |
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it seems has buffer in kernel layer and uart device layer, write() in non block mode, data is not sent to the net work immediately.