https://aznot.com/index.php?action=history&feed=atom&title=Linux%2FCustom_Buad_Rate 2026-05-09T01:22:02Z Revision history for this page on the wiki MediaWiki 1.41.0 https://aznot.com/index.php?title=Linux/Custom_Buad_Rate&diff=4214&oldid=prev 2017-03-13T21:21:05Z

<p>Created page with &quot;== Usage == screen /dev/ttyUSB3 linux-custom-baudrate /dev/ttyUSB3 115200 linux-custom-baudrate /dev/ttyUSB3 195360 # linux-custom-baudrate: actual baudrate is 60000000...&quot;</p> <p><b>New page</b></p><div>== Usage ==<br /> <br /> screen /dev/ttyUSB3<br /> <br /> linux-custom-baudrate /dev/ttyUSB3 115200<br /> <br /> linux-custom-baudrate /dev/ttyUSB3 195360<br /> # linux-custom-baudrate: actual baudrate is 60000000 / 307 = 195439.734375<br /> <br /> == Source ==<br /> <br /> linux-custom-baudrate.c:<br /> &lt;pre&gt;<br /> #include &lt;termio.h&gt;<br /> #include &lt;fcntl.h&gt;<br /> #include &lt;err.h&gt;<br /> #include &lt;linux/serial.h&gt;<br /> #include &lt;stdio.h&gt;<br /> <br /> static int rate_to_constant(int baudrate) {<br /> #define B(x) case x: return B##x<br /> switch(baudrate) {<br /> B(50); B(75); B(110); B(134); B(150);<br /> B(200); B(300); B(600); B(1200); B(1800);<br /> B(2400); B(4800); B(9600); B(19200); B(38400);<br /> B(57600); B(115200); B(230400); B(460800); B(500000); <br /> B(576000); B(921600); B(1000000);B(1152000);B(1500000); <br /> default: return 0;<br /> }<br /> #undef B<br /> } <br /> <br /> /* Open serial port in raw mode, with custom baudrate if necessary */<br /> int serial_open(const char *device, int rate)<br /> {<br /> struct termios options;<br /> struct serial_struct serinfo;<br /> int fd;<br /> int speed = 0;<br /> <br /> /* Open and configure serial port */<br /> if ((fd = open(device,O_RDWR|O_NOCTTY)) == -1)<br /> return -1;<br /> <br /> speed = rate_to_constant(rate);<br /> <br /> if (speed == 0) {<br /> /* Custom divisor */<br /> serinfo.reserved_char[0] = 0;<br /> if (ioctl(fd, TIOCGSERIAL, &amp;serinfo) &lt; 0)<br /> return -1;<br /> serinfo.flags &amp;= ~ASYNC_SPD_MASK;<br /> serinfo.flags |= ASYNC_SPD_CUST;<br /> serinfo.custom_divisor = (serinfo.baud_base + (rate / 2)) / rate;<br /> if (serinfo.custom_divisor &lt; 1) <br /> serinfo.custom_divisor = 1;<br /> if (ioctl(fd, TIOCSSERIAL, &amp;serinfo) &lt; 0)<br /> return -1;<br /> if (ioctl(fd, TIOCGSERIAL, &amp;serinfo) &lt; 0)<br /> return -1;<br /> if (serinfo.custom_divisor * rate != serinfo.baud_base) {<br /> warnx(&quot;actual baudrate is %d / %d = %f&quot;,<br /> serinfo.baud_base, serinfo.custom_divisor,<br /> (float)serinfo.baud_base / serinfo.custom_divisor);<br /> }<br /> }<br /> <br /> fcntl(fd, F_SETFL, 0);<br /> tcgetattr(fd, &amp;options);<br /> cfsetispeed(&amp;options, speed ?: B38400);<br /> cfsetospeed(&amp;options, speed ?: B38400);<br /> cfmakeraw(&amp;options);<br /> options.c_cflag |= (CLOCAL | CREAD);<br /> options.c_cflag &amp;= ~CRTSCTS;<br /> if (tcsetattr(fd, TCSANOW, &amp;options) != 0)<br /> return -1;<br /> <br /> return fd;<br /> }<br /> <br /> void main(int argc, char *argv[])<br /> {<br /> if (serial_open(argv[1], atoi(argv[2])) &lt; 0)<br /> {<br /> fprintf(stderr, &quot;failed\n&quot;);<br /> }<br /> pause();<br /> }<br /> &lt;/pre&gt;<br /> <br /> Source: https://jim.sh/ftx/files/linux-custom-baudrate.c<br /> <br /> Reference:<br /> * linux - C code for non-standard baud rate on Debian/Raspberry Pi - Stack Overflow - http://stackoverflow.com/questions/23492088/c-code-for-non-standard-baud-rate-on-debian-raspberry-pi<br /> <br /> <br /> === Compile ===<br /> <br /> gcc linux-custom-baudrate.c -o linux-custom-baudrate<br /> <br /> cp linux-custom-buadrate /usr/local/sbin/</div>

Kenneth