https://www.aliexpress.com/item/32990413968.html
RS232 시리얼포트로 제어되는 4채널 릴레이 제품을 샀습니다.

https://onedrive.live.com/redir?resid=3DFF9FAEE8435679!15927&authkey=!AG1AzoSlnv7JM4g&ithint=file%2crar
그런데 제공하는 소프트웨어는 윈도우용 C#으로 짜여진 코드 뿐이네요.

단순하게 그냥 16진수값을 write하면 되는걸로 생각하고 리눅스에서 C코드를 작성하였으나 동작이 안되네요.

무언가 IC를 제어하는 별도의 라이브러리가 필요한것일까요?

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#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <termios.h>
#include <unistd.h>

#include <sys/types.h>
#include <sys/stat.h>

#define COM3    "/dev/ttyS0"

static int fd3;

// 시리얼포트 속성처리용 구조체
struct termios newtio3;

int serial_init(void)
{
    fd3 = open(COM3, O_RDWR | O_NOCTTY);

    // COM1 시리얼 속성 셋팅
    memset(&newtio3, 0, sizeof(newtio3));

    cfsetispeed(&newtio3, B9600);
    cfsetospeed(&newtio3, B9600);

    newtio3.c_cflag |= PARENB;
    newtio3.c_cflag &= ~PARODD;
    newtio3.c_cflag &= ~CSTOPB;
    newtio3.c_cflag &= ~CSIZE;
    newtio3.c_cflag |= CS8;

    newtio3.c_cflag |= CLOCAL;
    newtio3.c_cflag |= CREAD;
    newtio3.c_iflag = IGNPAR;
    newtio3.c_oflag = 0;
    newtio3.c_lflag = 0;
    newtio3.c_cc[VTIME] = 0;
    newtio3.c_cc[VMIN] = 1;

    tcflush (fd3, TCIFLUSH);
    tcsetattr(fd3, TCSANOW, &newtio3);

    return 0;
}

int main(int argc, char* argv[])
{
    int bytes, i;
    char buf[4][8];
    char momentary[8];

    serial_init();

    memset(momentary, 0x00, 8);

    momentary[0] = 0x55; momentary[1] = 0x56; momentary[2] = 0x00; momentary[3] = 0x00;
    momentary[4] = 0x00; momentary[5] = 0x01; momentary[6] = 0x04; momentary[7] = 0xB0;

    //setvbuf(stdout, NULL, _IOFBF, 0);

    bytes = write(fd3, momentary, 8);

#if 0
    for(i=0;i<4;i++)
    {
        memset(buf[i], 0x00, 8);
    }

    // Relay Open
    buf[0][0] = 0x55; buf[0][1] = 0x56; buf[0][2] = 0x00; buf[0][3] = 0x00; buf[0][4] = 0x00; buf[0][5] = 0x01; buf[0][6] = 0x01; buf[0][7] = 0xAD;
    buf[1][0] = 0x55; buf[1][1] = 0x56; buf[1][2] = 0x00; buf[1][3] = 0x00; buf[1][4] = 0x00; buf[1][5] = 0x02; buf[1][6] = 0x01; buf[1][7] = 0xAE;
    buf[2][0] = 0x55; buf[2][1] = 0x56; buf[2][2] = 0x00; buf[2][3] = 0x00; buf[2][4] = 0x00; buf[2][5] = 0x03; buf[2][6] = 0x01; buf[2][7] = 0xAF;
    buf[3][0] = 0x55; buf[3][1] = 0x56; buf[3][2] = 0x00; buf[3][3] = 0x00; buf[3][4] = 0x00; buf[3][5] = 0x04; buf[3][6] = 0x01; buf[3][7] = 0xB0;

    for(i=0;i<4;i++)
    {
        write(fd3, buf[i], 8);
        sleep(1);
    }

    // Relay Close
    buf[0][0] = 0x55; buf[0][1] = 0x56; buf[0][2] = 0x00; buf[0][3] = 0x00; buf[0][4] = 0x00; buf[0][5] = 0x01; buf[0][6] = 0x02; buf[0][7] = 0xAE;
    buf[1][0] = 0x55; buf[1][1] = 0x56; buf[1][2] = 0x00; buf[1][3] = 0x00; buf[1][4] = 0x00; buf[1][5] = 0x02; buf[1][6] = 0x02; buf[1][7] = 0xAF;
    buf[2][0] = 0x55; buf[2][1] = 0x56; buf[2][2] = 0x00; buf[2][3] = 0x00; buf[2][4] = 0x00; buf[2][5] = 0x03; buf[2][6] = 0x02; buf[2][7] = 0xB0;
    buf[3][0] = 0x55; buf[3][1] = 0x56; buf[3][2] = 0x00; buf[3][3] = 0x00; buf[3][4] = 0x00; buf[3][5] = 0x04; buf[3][6] = 0x02; buf[3][7] = 0xB1;

    for(i=0;i<4;i++)
    {
        write(fd3, buf[i], 8);
        sleep(1);
    }
#endif
    close(fd3);

    return 0;
}