Serial call/response

gistfile1.c

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

struct tempduino_data
{
  int fd;
  char buf[64];
};

/* readwrite() writes a byte and reads the response */
int readwrite(struct tempduino_data *d)
{

  /* fill buffer with temporary data */
  sprintf(d->buf, "test");
  /* write a byte */
  write_tempduino_byte(d);
  /* read the response */
  read_tempduino(d);

  return 1;
}

/* open the serial port file descriptor */
int init_serial_fd(char *ttyname, struct tempduino_data *d)
{
  /* open the file descriptor */
  d->fd = open(ttyname, O_RDWR | O_NOCTTY);

  printf("fd opened as %i\n", d->fd);
  
  /* wait for the Arduino to reboot */
  usleep(3500000);

  return 1;
}

/* set the serial options to canonical */
int init_serial_options(int fd)
{
  struct termios toptions;
  
  tcgetattr(fd, &toptions);

  /* 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_iflag |= ICANON;

  tcsetattr(fd, TCSANOW, &toptions);

  return 1;
}
  
/* write a byte */
int write_tempduino_byte(struct tempduino_data *d)
{
  char *str = "1";
  int n;

  n = write(d->fd, str, 1);

  printf("%i bytes written\n", n);
  
  return 1;
}

/* read what the Arduino sends */
int read_tempduino(struct tempduino_data *d)
{
  int n;

  n = read(d->fd, d->buf, 64);
  /* terminating zero in the string */
  d->buf[n] = 0;

  printf("%i bytes read, buffer contains: %s\n", n, d->buf);

  return 1;
}
  
int main(int argc, char *argv[])
{
  struct tempduino_data w;

  init_serial_fd("/dev/ttyACM0", &w);

  init_serial_options(w.fd);
  
  readwrite(&w);
  readwrite(&w);
  readwrite(&w);

  return 0;
}