1 files changed, 85 insertions, 0 deletions
diff --git a/serial.c b/serial.c
new file mode 100644
index 0000000..63e8ba7
--- /dev/null
+++ b/serial.c
@@ -0,0 +1,85 @@
+#include <errno.h>
+#include <fcntl.h> 
+#include <string.h>
+#include <termios.h>
+#include <unistd.h>
+
+int
+set_interface_attribs (int fd, int speed, int parity)
+{
+        struct termios tty;
+        memset (&tty, 0, sizeof tty);
+        if (tcgetattr (fd, &tty) != 0)
+        {
+                error_message ("error %d from tcgetattr", errno);
+                return -1;
+        }
+
+        cfsetospeed (&tty, speed);
+        cfsetispeed (&tty, speed);
+
+        tty.c_cflag = (tty.c_cflag & ~CSIZE) | CS8;     // 8-bit chars
+        // disable IGNBRK for mismatched speed tests; otherwise receive break
+        // as \000 chars
+        tty.c_iflag &= ~IGNBRK;         // disable break processing
+        tty.c_lflag = 0;                // no signaling chars, no echo,
+                                        // no canonical processing
+        tty.c_oflag = 0;                // no remapping, no delays
+        tty.c_cc[VMIN]  = 0;            // read doesn't block
+        tty.c_cc[VTIME] = 5;            // 0.5 seconds read timeout
+
+        tty.c_iflag &= ~(IXON | IXOFF | IXANY); // shut off xon/xoff ctrl
+
+        tty.c_cflag |= (CLOCAL | CREAD);// ignore modem controls,
+                                        // enable reading
+        tty.c_cflag &= ~(PARENB | PARODD);      // shut off parity
+        tty.c_cflag |= parity;
+        tty.c_cflag &= ~CSTOPB;
+        tty.c_cflag &= ~CRTSCTS;
+
+        if (tcsetattr (fd, TCSANOW, &tty) != 0)
+        {
+                error_message ("error %d from tcsetattr", errno);
+                return -1;
+        }
+        return 0;
+}
+
+void
+set_blocking (int fd, int should_block)
+{
+        struct termios tty;
+        memset (&tty, 0, sizeof tty);
+        if (tcgetattr (fd, &tty) != 0)
+        {
+                error_message ("error %d from tggetattr", errno);
+                return;
+        }
+
+        tty.c_cc[VMIN]  = should_block ? 1 : 0;
+        tty.c_cc[VTIME] = 5;            // 0.5 seconds read timeout
+
+        if (tcsetattr (fd, TCSANOW, &tty) != 0)
+                error_message ("error %d setting term attributes", errno);
+}
+
+
+...
+char *portname = "/dev/ttyUSB1"
+ ...
+int fd = open (portname, O_RDWR | O_NOCTTY | O_SYNC);
+if (fd < 0)
+{
+        error_message ("error %d opening %s: %s", errno, portname, strerror (errno));
+        return;
+}
+
+set_interface_attribs (fd, B115200, 0);  // set speed to 115,200 bps, 8n1 (no parity)
+set_blocking (fd, 0);                // set no blocking
+
+write (fd, "hello!\n", 7);           // send 7 character greeting
+
+usleep ((7 + 25) * 100);             // sleep enough to transmit the 7 plus
+                                     // receive 25:  approx 100 uS per char transmit
+char buf [100];
+int n = read (fd, buf, sizeof buf);  // read up to 100 characters if ready to read