将命令发送到串行设备并接收响应

Question

我试图向串行设备（arduino）发送命令并接收响应，该命令通过了，但是我没有从目标设备获得响应。

我希望C程序通过发送和接收数据来控制串行设备。

Arduino代码：

void setup() {
    // initialize serial communication:
    Serial.begin(9600);
}

void loop() {
    if (Serial.available() > 0) {
        int inByte = Serial.read();
        switch (inByte) {
          case 'H':
              Serial.print("75864d63001bebaa");
              break;
        }
    }
}

C代码：

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdint.h>
#include <fcntl.h>
#include <termios.h>
#include <errno.h>
#include <sys/ioctl.h>


int main(int argc, char *argv[]) {
    int fd, n, i;
    char buf[64] = "temp text";
    struct termios toptions;

    /* open serial port */
    fd = open("/dev/ttyACM0", O_RDWR | O_NOCTTY);
    printf("fd opened as %i\n", fd);

    /* wait for the Arduino to reboot */
    usleep(3500000);

    /* get current serial port settings */
    tcgetattr(fd, &toptions);
    /* set 9600 baud both ways */
    cfsetispeed(&toptions, B9600);
    cfsetospeed(&toptions, B9600);
    /* 8 bits, no parity, no stop bits */
    toptions.c_cflag &= ~PARENB;
    toptions.c_cflag &= ~CSTOPB;
    toptions.c_cflag &= ~CSIZE;
    toptions.c_cflag |= CS8;
    /* Canonical mode */
    toptions.c_lflag |= ICANON;
    /* commit the serial port settings */
    tcsetattr(fd, TCSANOW, &toptions);

    /* Send byte to trigger Arduino to send string back */
    write(fd, "H", 1);

    /* Receive string from Arduino */
    n = read(fd, buf, 64);
    /* insert terminating zero in the string */
    buf[n] = 0;

    printf("%i bytes read, buffer contains: %s\n", n, buf);
    return 0;
}