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POSerial port not reading
 

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    <p>I've got this strange issue with reading from a serial port on Linux. About 50% of the time, I won't get any data back from the serial port when I'm reading from it, yet if I use GTKTerm I get data back 100% of the time. I've double-checked my settings, and the terminal settings that I'm using are the exact same that GTKTerm uses, so I'm mystified as to why this would occur. The only thing that I could think of is that the port is set in canonical mode, not raw mode, but I set it properly - the device that I'm reading from does not send back newlines with all of the commands. However, everything is working properly when the device sends back commands with a newline character.</p> <p>Here's the code I'm using:</p> <pre><code>int fd = open(serial_port, O_RDWR ); if( fd &lt; 0 ){ perror("open"); } //Set the serial port settings struct termios newio; if( tcgetattr( fd, &amp;newio ) &lt; 0 ) perror("tcgetattr"); if( cfsetospeed( &amp;newio, B9600 ) &lt; 0 ) perror("cfsetospeed"); newio.c_cflag &amp;= ~CSTOPB; newio.c_cflag &amp;= ~CSIZE; newio.c_cflag |= CS8; newio.c_cflag |= CREAD; newio.c_iflag |= IGNPAR; newio.c_iflag |= IGNBRK; newio.c_iflag &amp;= ~BRKINT; newio.c_iflag &amp;= ~ICRNL; newio.c_iflag &amp;= ~IXON; newio.c_cflag |= CLOCAL; newio.c_oflag = 0; newio.c_lflag = 0; newio.c_cc[VTIME] = 0; newio.c_cc[VMIN] = 1; if( tcsetattr( fd, TCSANOW, &amp;newio ) &lt; 0 ) perror("tcsetattr"); tcflush( fd, TCOFLUSH ); tcflush( fd, TCIFLUSH ); </code></pre> <p><strong>Reading code (in separate thread)</strong></p> <pre><code>void* thr(void* ign){ char buffer[10]; while( 1 ){ int got = read(fd, buffer, 10); buffer[got] = 0; printf("got %s\n", buffer); } } </code></pre>
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    1. COCan you include an example of the code you're using to read/write from that fd? You may also want to `strace` GTKTerm and your code and pick out the `TCSETS` ioctl call from each to compare.
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    2. CO@rm5248: The code which configures the port seems okay. Maybe how the i/o is done is the problem. Also, be sure to carefully compare the port settings with `stty -a -F /dev/ttyWhatever` when your program has it open and when GTK has it open to see if anything is different.
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    3. COWell, after checking with stty, the only difference between what I have and what GTKTerm has is hupcl, which shouldn't matter because what I'm connecting to only uses the transmit/receive lines. I edited in the reading code, writing code is essentially the same.
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