Serial port polling not working on Beaglebone Black - c++

Question

I simply cannot get the poll() function to respond to data being sent over UART1 / /dev/ttyO1. Code as follows, maybe someone can spot my silly mistake?
#include <stdio.h>
#include <termios.h>
#include <fcntl.h>
#include <string.h>
#include <sys/types.h>
#include <sys/poll.h>
#include <time.h>
#include <errno.h>
#include <unistd.h>
int openPort()
{
struct termios oldtio, newtio;
int fd = open("/dev/ttyO1",O_RDWR|O_NOCTTY|O_NONBLOCK|O_NDELAY);
if (fd == -1)
{
printf( "could not open tty" );
return -1;
}
if ( tcgetattr( fd, &oldtio ) == -1 )
{
printf( "error getting tcattr\n" );
close( fd );
return -1;
}
cfmakeraw( &newtio );
cfsetispeed( &newtio, B9600 );
cfsetospeed( &newtio, B9600 );
newtio.c_cflag = (newtio.c_cflag & ~CSIZE) | CS8 | B9600;
newtio.c_cflag |= (CLOCAL | CREAD);
newtio.c_cflag &= ~(PARENB | PARODD);
newtio.c_cflag &= ~CRTSCTS;
newtio.c_cflag &= ~CSTOPB;
newtio.c_iflag = 0;//IGNPAR;
//newtio.c_iflag &= ~(IXON | IXOFF | IXANY);
newtio.c_lflag = 0;
newtio.c_oflag = 0;
newtio.c_cc[VTIME] = 0;
newtio.c_cc[VMIN] = 1;
tcflush( fd, TCIOFLUSH );
if ( tcsetattr( fd, TCSANOW, &newtio ) == -1 )
{
close( fd );
printf( "error setting attrs\n" );
return -1;
}
return fd;
}
void selectLoop( int fd )
{
struct pollfd fds[1];
fds[0].fd = fd;
fds[0].events = POLLIN;
int rc = poll( fds, 1, 100000 );
if (rc < 0)
{
perror( "poll" );
}
else if (rc > 0)
{
char buffer[32] = {0};
int r = read( fd, buffer, sizeof(buffer) );
if (r == -1)
{
printf( "error: %s\n", strerror( errno ) );
}
else
{
printf( buffer );
}
}
else
{
printf( "No data\n" );
}
//close( fd );
sleep( 1 );
}
int main( int c, char ** v )
{
int fd = openPort();
if (fd >= 0)
{
while(1)
{
selectLoop(fd);
}
}
return 0;
}
I get the same result using select(). However if I attach a signal to "data received" then the signal fires, though this is a scenario I am trying to avoid as it plays havoc with Netbeans' debug environment.
FYI: board revision is B6, UART1 is connected by TX/RX only. The "screen" program successfully receives and sends characters from the UART, so I know that it fundamentally works.

Answer 1

Replace this with something sensible:
printf( buffer );
Perhaps:
for (int i = 0; i < r; ++i)
putchar(buffer[i]);
fflush(stdout);
This flushes and doesn't risk printing more characters than read if the buffer is full.