Reading arduino serial in linux using C - c

Question

I want to read serial from arduino. I use this code :
#include <stdio.h> /* Standard input/output definitions */
#include <string.h> /* String function definitions */
#include <unistd.h> /* UNIX standard function definitions */
#include <fcntl.h> /* File control definitions */
#include <errno.h> /* Error number definitions */
#include <termios.h> /* POSIX terminal control definitions */
#include <sys/ioctl.h>
int main(){
char data[1024];
char dev[] = "/dev/ttyACM1";
int fd = open(dev, O_RDWR | O_NOCTTY | O_NDELAY);
fcntl(fd, F_SETFL, FNDELAY);
struct termios options;
tcgetattr(fd, &options);
cfsetispeed(&options, B9600);
cfsetospeed(&options, B9600);
options.c_cflag |= CS8;
options.c_cflag |= CS8;
options.c_cflag &= ~CRTSCTS;
options.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
tcsetattr(fd, TCSANOW, &options);
ioctl(fd, TCFLSH, 2);
while(1){
read(fd, data, sizeof(data));
printf(data);
}
//write(fd, data, sizeof(data));
}
My arduino runs very simple sketch :
int x;
void setup() {
Serial.begin(9600);
}
void loop() {
Serial.println("DO YOU HEAR ME ??");
delay(1000);
}
and output of this combinatin is that :
??OU HEAR ME ??
DO YOU HEAR ME ??
DO YOU HEAR ME ??
A¹­þ
??OU HEAR ME ??
DO YOU HEAR ME ??
DO YOU HEAR ME ??
A¹­þ
??OU HEAR ME ??
DO YOU HEAR ME ??
DO YOU HEAR ME ??
My question is how to make order out of chaos. I found that this issue occurs when buffer ends and new one begins(bigger buffer less junk data) but I can't have a infinite buffer. Also there is a lot of junk when it reads for the first time.. Is there a way to sync it or something ?
(Also I am not native English sorry for any mistakes.)

Answer 1

I found answer to my own problem. I used this time c++ to organize it in class (very poor one because it doesn't handle any errors and doesn't use c++ in the most..) Here is the code :
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <termios.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <strings.h>
#include <cstring>
#include <iostream>
//Here I define some vars
#define BAUDRATE B9600
#define MODEMDEVICE "/dev/ttyACM0"
#define _POSIX_SOURCE 1
class serial{
public:
serial(){
fd = open(MODEMDEVICE, O_RDWR | O_NOCTTY );
if (fd <0) {perror(MODEMDEVICE); exit(-1); }
// Improvement No. 1 I save old setting and clean the new one
tcgetattr(fd,&oldtio);
bzero(&newtio, sizeof(newtio));
// Here I set all the flags to vars at once
newtio.c_cflag = BAUDRATE | CRTSCTS | CS8 | CLOCAL | CREAD;
newtio.c_iflag = IGNPAR | ICRNL;
newtio.c_oflag = 0;
newtio.c_lflag = ICANON;
//here I set some new flags..
newtio.c_cc[VINTR] = 0; /* Ctrl-c */
newtio.c_cc[VQUIT] = 0; /* Ctrl-\ */
newtio.c_cc[VERASE] = 0; /* del */
newtio.c_cc[VKILL] = 0; /* # */
newtio.c_cc[VEOF] = 4; /* Ctrl-d */
newtio.c_cc[VTIME] = 0; /* inter-character timer unused */
newtio.c_cc[VMIN] = 1; /* blocking read until 1 character arrives */
newtio.c_cc[VSWTC] = 0; /* '\0' */
newtio.c_cc[VSTART] = 0; /* Ctrl-q */
newtio.c_cc[VSTOP] = 0; /* Ctrl-s */
newtio.c_cc[VSUSP] = 0; /* Ctrl-z */
newtio.c_cc[VEOL] = 0; /* '\0' */
newtio.c_cc[VREPRINT] = 0; /* Ctrl-r */
newtio.c_cc[VDISCARD] = 0; /* Ctrl-u */
newtio.c_cc[VWERASE] = 0; /* Ctrl-w */
newtio.c_cc[VLNEXT] = 0; /* Ctrl-v */
newtio.c_cc[VEOL2] = 0; /* '\0' */
// and I finally save the settings
tcflush(fd, TCIFLUSH);
tcsetattr(fd,TCSANOW,&newtio);
}
~serial(){
close(fd);
}
std::string sread(){
res = read(fd,buf,255);
buf[res]=0;
return buf;
}
void swrite(const char* input){
write(fd,input,std::strlen(input));
}
private:
int fd,c,res;
struct termios oldtio,newtio;
char buf[255];
};
int main(){
serial s;
s.swrite("Light");
std::string buf = s.sread();
std::cout << buf;
}
This is more of a ripoff from "Serial programming HOW TO" : http://tldp.org/HOWTO/Serial-Programming-HOWTO/ (form the example code..)
And here is the new poor arduino code :
int x;
String buff;
int lpin = A0;
int tpin = A1;
int data;
void setup() {
Serial.begin(9600);
pinMode(lpin,INPUT);
pinMode(tpin,INPUT);
}
void loop() {
if(Serial.available() == 1)
{
buff = Serial.readString();
if(buff == "Light"){
data = analogRead(lpin);
Serial.print(data);
Serial.print("\n");
}else if(buff == "Temp"){
data = analogRead(tpin);
Serial.print(data);
Serial.print("\n");
}else{
Serial.print("Something went wrong !");
Serial.print("\n");
}
}
delay(1);
}