# vi  serial.c
/*
 Pi_Serial_test.cpp - SerialProtocol library - demo
 Copyright (c) 2014 NicoHood.  All right reserved.
 Program to test serial communication
 
 Compile with:
 sudo gcc -o Pi_Serial_Test.o Pi_Serial_Test.cpp -lwiringPi -DRaspberryPi -pedantic -Wall
 sudo ./Pi_Serial_Test.o
 */
 
// just that the Arduino IDE doesnt compile these files.
#ifdef RaspberryPi
 
//include system librarys
#include <stdio.h> //for printf
#include <stdint.h> //uint8_t definitions
#include <stdlib.h> //for exit(int);
#include <string.h> //for errno
#include <errno.h> //error output
 
//wiring Pi
#include <wiringPi.h>
#include <wiringSerial.h>
 
// Find Serial device on Raspberry with ~ls /dev/tty*
// ARDUINO_UNO "/dev/ttyACM0"
// FTDI_PROGRAMMER "/dev/ttyUSB0"
// HARDWARE_UART "/dev/ttyAMA0"
char device[]= "/dev/ttyACM0";
// filedescriptor
int fd;
unsigned long baud = 9600;
unsigned long time=0;
 
//prototypes
int main(void);
void loop(void);
void setup(void);
 
void setup(){
 
  printf("%s \n", "Raspberry Startup!");
  fflush(stdout);
 
  //get filedescriptor
  if ((fd = serialOpen (device, baud)) < 0){
    fprintf (stderr, "Unable to open serial device: %s\n", strerror (errno)) ;
    exit(1); //error
  }
 
  //setup GPIO in wiringPi mode
  if (wiringPiSetup () == -1){
    fprintf (stdout, "Unable to start wiringPi: %s\n", strerror (errno)) ;
    exit(1); //error
  }
 
}
 
void loop(){
  // Pong every 3 seconds
  if(millis()-time>=3000){
    serialPuts (fd, "Pong!\n");
    // you can also write data from 0-255
    // 65 is in ASCII 'A'
    serialPutchar (fd, 65);
    time=millis();
  }
 
  // read signal
  if(serialDataAvail (fd)){
    char newChar = serialGetchar (fd);
    printf("%c", newChar);
    fflush(stdout);
  }
 
}
 
// main function for normal c++ programs on Raspberry
int main(){
  setup();
  while(1) loop();
  return 0;
}
 
#endif //#ifdef RaspberryPi

$ sudo gcc test.c -o serial -l wiringPi -DRaspberryPi
$ sudo ./serai

################
아두이노
#############
void setup(){ 
  Serial.begin(9600);
}
 
void loop(){
  Serial.println("Hello World");
  delay(1000);
}