How to wait for serial input in raw (noncanonical) mode? - c++

Question

This program runs on PC and I want him wait until there are data available on serial connection from Arduino, and display them. If Arduino don't send anything, I want the program to wait indefinitely.
What happens, is that I've got only Resource temporarily unavailable messages.
After kind help from Kurt Stutsman here is a working program that waits for binary input from serial connection, (from the Arduino in this case).
#include <string.h>
#include <iostream>
#include <stdint.h>
#include <errno.h>
#include <fcntl.h> // File control definitions
#include <termios.h> // POSIX terminal control definitions
#include <unistd.h> // UNIX standard function definitions
using namespace std;
int connect(const char* serialport)
{
struct termios toptions;
int fd;
fd = open(serialport, O_RDWR );
if (fd == -1) {
return -1;
}
if (tcgetattr(fd, &toptions) < 0)
return -1;
speed_t brate = B9600; //9600 bauds
cfsetospeed(&toptions, brate);
cfmakeraw(&toptions);
toptions.c_cc[VMIN] = 1; //I want read to wait for the input
toptions.c_cc[VTIME] = 0; //indefinitely, until it arrives. Byte after byte.
tcsetattr(fd, TCSANOW, &toptions);
if( tcsetattr(fd, TCSAFLUSH, &toptions) < 0) {
return -1;
}
return fd;
}
int main() {
int fd = connect("/dev/ttyACM0");
if (fd==-1)
{
cout<<"Error in opening serial port\n";
cout<<strerror(errno)<<'\n';
return -1;
}
while(true)
{
uint8_t b=0;
int ret=read(fd, &b, 1);
if (ret == 1)
{
cout<<"received byte "<<int(b)<<'\n';
} else if (ret == 0)
{
cout<<"EOF\n";
} else
{
cout<<strerror(errno)<<'\n';
}
}
return 0;
}
You can test it with this simple Arduino C++ code:
void setup() {
Serial.begin(9600); // connect to the serial port
}
void loop()
{
Serial.write(uint8_t(42));
delay(1000);
}