🖱️UART

UART RASPBERRY PI

UART

An UART connection can be established with common C libraries. Following the very detailed explanation in this article, you will need to open the device, then define various properties of the TTY device by using a termios struct, and then write to and read from the serial port.

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

int main() {
  int serial_port = open("/dev/ttyUSB0", O_RDWR);

  struct termios tty;

  if(tcgetattr(serial_port, &tty) != 0) {
      printf("Error %i from tcgetattr: %s\n", errno, strerror(errno));
      return 1;
  }

  tty.c_cflag &= ~PARENB;
  tty.c_cflag &= ~CSTOPB;
  tty.c_cflag &= ~CSIZE;
  tty.c_cflag |= CS8;
  tty.c_cflag &= ~CRTSCTS;
  tty.c_cflag |= CREAD | CLOCAL;

  tty.c_lflag &= ~ICANON;
  tty.c_lflag &= ~ECHO;
  tty.c_lflag &= ~ECHOE;
  tty.c_lflag &= ~ECHONL;
  tty.c_lflag &= ~ISIG;
  tty.c_iflag &= ~(IXON | IXOFF | IXANY);
  tty.c_iflag &= ~(IGNBRK|BRKINT|PARMRK|ISTRIP|INLCR|IGNCR|ICRNL);

  tty.c_oflag &= ~OPOST;
  tty.c_oflag &= ~ONLCR;

  tty.c_cc[VTIME] = 10;
  tty.c_cc[VMIN] = 0;

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

  if (tcsetattr(serial_port, TCSANOW, &tty) != 0) {
      printf("Error %i from tcsetattr: %s\n", errno, strerror(errno));
      return 1;
  }

  unsigned char msg[] = { 'H', 'e', 'l', 'l', 'o', '\r' };
  write(serial_port, "Hello, world!", sizeof(msg));

  char read_buf [256];

  memset(&read_buf, '\0', sizeof(read_buf);

  int num_bytes = read(serial_port, &read_buf, sizeof(read_buf));

  if (num_bytes < 0) {
      printf("Error reading: %s", strerror(errno));
      return 1;
  }

  printf("Read %i bytes. Received message: %s", num_bytes, read_buf);

  close(serial_port)
  return 0;