RS232 UART （Universal Asynchronous Receiver / Transmitter）

#include <stdio.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>

void main()
{
    int fd;
    char *uart3 = "/dev/ttySAC3";

    if ((fd = open(uart3, O_RDWR | O_CREAT, 0777)) < 0)
    {
        printf("open %s failed!\n", uart3);
    }
    else
    {
        printf("open %s is success!\n", uart3);
    }

    close(fd);
}

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <termios.h>
#include <errno.h>

int set_opt(int, int, int, char, int);
void main()
{
    int fd, wr_static, i = 10;
    char *uart3 = "/dev/ttySAC3";
    char *buffer = "hello world!\n";

    printf("\r\nitop4412 uart3 writetest start\r\n");

    if ((fd = open(uart3, O_RDWR | O_NOCTTY | O_NDELAY)) < 0)
    {
        printf("open %s is failed", uart3);
    }
    else
    {
        printf("open %s is success\n", uart3);
        set_opt(fd, 115200, 8, 'N', 1);
        while (i--)
        {
            wr_static = write(fd, buffer, strlen(buffer));
            if (wr_static < 0)
                printf("write failed\n");
            else
            {
                printf("wr_static is %d\n", wr_static);
            }
            sleep(1);
        }
    }
    close(fd);
}

int set_opt(int fd, int nSpeed, int nBits, char nEvent, int nStop)
{
    struct termios newtio, oldtio;
    if (tcgetattr(fd, &oldtio) != 0)
    {
        perror("SetupSerial 1");
        return -1;
    }
    bzero(&newtio, sizeof(newtio));
    newtio.c_cflag |= CLOCAL | CREAD;
    newtio.c_cflag &= ~CSIZE;

    switch (nBits)
    {
    case 7:
        newtio.c_cflag |= CS7;
        break;
    case 8:
        newtio.c_cflag |= CS8;
        break;
    }

    switch (nEvent)
    {
    case 'O':
        newtio.c_cflag |= PARENB;
        newtio.c_cflag |= PARODD;
        newtio.c_iflag |= (INPCK | ISTRIP);
        break;
    case 'E':
        newtio.c_iflag |= (INPCK | ISTRIP);
        newtio.c_cflag |= PARENB;
        newtio.c_cflag &= ~PARODD;
        break;
    case 'N':
        newtio.c_cflag &= ~PARENB;
        break;
    }

    switch (nSpeed)
    {
    case 2400:
        cfsetispeed(&newtio, B2400);
        cfsetospeed(&newtio, B2400);
        break;
    case 4800:
        cfsetispeed(&newtio, B4800);
        cfsetospeed(&newtio, B4800);
        break;
    case 9600:
        cfsetispeed(&newtio, B9600);
        cfsetospeed(&newtio, B9600);
        break;
    case 115200:
        cfsetispeed(&newtio, B115200);
        cfsetospeed(&newtio, B115200);
        break;
    case 460800:
        cfsetispeed(&newtio, B460800);
        cfsetospeed(&newtio, B460800);
        break;
    default:
        cfsetispeed(&newtio, B9600);
        cfsetospeed(&newtio, B9600);
        break;
    }
    if (nStop == 1)
        newtio.c_cflag &= ~CSTOPB;
    else if (nStop == 2)
        newtio.c_cflag |= CSTOPB;
    newtio.c_cc[VTIME] = 0;
    newtio.c_cc[VMIN] = 0;
    tcflush(fd, TCIFLUSH);
    if ((tcsetattr(fd, TCSANOW, &newtio)) != 0)
    {
        perror("com set error");
        return -1;
    }
    //  printf("set done!\n\r");
    return 0;
}

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <termios.h>
#include <errno.h>

int set_opt(int, int, int, char, int);
//"/dev/ttySAC3"是con2，靠近耳机接口的串口
void main()
{
    int fd, nByte;
    char *uart3 = "/dev/ttySAC3";
    char buffer[512];
    char *uart_out = "please input\r\n";
    memset(buffer, 0, sizeof(buffer));
    if ((fd = open(uart3, O_RDWR | O_NOCTTY)) < 0)
        printf("open %s is failed", uart3);
    else
    {
        set_opt(fd, 115200, 8, 'N', 1);
        write(fd, uart_out, strlen(uart_out));
        while (1)
        {
            while ((nByte = read(fd, buffer, 512)) > 0)
            {
                buffer[nByte + 1] = '\0';
                write(fd, buffer, strlen(buffer));
                memset(buffer, 0, strlen(buffer));
                nByte = 0;
            }
        }
    }
}

int set_opt(int fd, int nSpeed, int nBits, char nEvent, int nStop)
{
    struct termios newtio, oldtio;
    if (tcgetattr(fd, &oldtio) != 0)
    {
        perror("SetupSerial 1");
        return -1;
    }
    bzero(&newtio, sizeof(newtio));
    newtio.c_cflag |= CLOCAL | CREAD;
    newtio.c_cflag &= ~CSIZE;

    switch (nBits)
    {
    case 7:
        newtio.c_cflag |= CS7;
        break;
    case 8:
        newtio.c_cflag |= CS8;
        break;
    }

    switch (nEvent)
    {
    case 'O':
        newtio.c_cflag |= PARENB;
        newtio.c_cflag |= PARODD;
        newtio.c_iflag |= (INPCK | ISTRIP);
        break;
    case 'E':
        newtio.c_iflag |= (INPCK | ISTRIP);
        newtio.c_cflag |= PARENB;
        newtio.c_cflag &= ~PARODD;
        break;
    case 'N':
        newtio.c_cflag &= ~PARENB;
        break;
    }

    switch (nSpeed)
    {
    case 2400:
        cfsetispeed(&newtio, B2400);
        cfsetospeed(&newtio, B2400);
        break;
    case 4800:
        cfsetispeed(&newtio, B4800);
        cfsetospeed(&newtio, B4800);
        break;
    case 9600:
        cfsetispeed(&newtio, B9600);
        cfsetospeed(&newtio, B9600);
        break;
    case 115200:
        cfsetispeed(&newtio, B115200);
        cfsetospeed(&newtio, B115200);
        break;
    case 460800:
        cfsetispeed(&newtio, B460800);
        cfsetospeed(&newtio, B460800);
        break;
    default:
        cfsetispeed(&newtio, B9600);
        cfsetospeed(&newtio, B9600);
        break;
    }
    if (nStop == 1)
        newtio.c_cflag &= ~CSTOPB;
    else if (nStop == 2)
        newtio.c_cflag |= CSTOPB;
    newtio.c_cc[VTIME] = 0;
    newtio.c_cc[VMIN] = 0;
    tcflush(fd, TCIFLUSH);
    if ((tcsetattr(fd, TCSANOW, &newtio)) != 0)
    {
        perror("com set error");
        return -1;
    }

    //  printf("set done!\n\r");
    return 0;
}