Adds NonBlocking Mode and ReadTimeout Config

- Read can be set to non-blocking mode - In NonBlocking Mode, ReadTimeout can be specified
tarm · Jan 17, 2015 · ff5de8d · ff5de8d
1 parent 6517d24
commit ff5de8d
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Showing 5 changed files with 48 additions and 13 deletions.
diff --git a/README.md b/README.md
@@ -58,6 +58,15 @@ func main() {
 }
 ```
 
+NonBlocking Mode
+----------------
+
+```go	
+	c := &serial.Config{Name: "COM45", Baud: 115200, NonBlockingRead: true, ReadTimeout: 1000}
+	// On Windows, ReadTimeout is in milliseconds (1000 = 1sec)
+	// where as on Linux and POSIX systems, ReadTimeout is in deciseconds (10 = 1sec)
+```
+
 Possible Future Work
 -------------------- 
 - better tests (loopback etc)
diff --git a/serial.go b/serial.go
@@ -65,11 +65,13 @@ import "io"
 //
 // For example:
 //
-//    c0 := &serial.Config{Name: "COM45", Baud: 115200}
+//    c0 := &serial.Config{Name: "COM45", Baud: 115200, NonBlockingRead: true, ReadTimeout: 1000}
 // or
 //    c1 := new(serial.Config)
 //    c1.Name = "/dev/tty.usbserial"
 //    c1.Baud = 115200
+//    c1.NonBlockingRead = true
+//    c1.ReadTimeout = 1000
 //
 type Config struct {
 	Name string
@@ -84,12 +86,13 @@ type Config struct {
 	// XONFlowControl bool
 
 	// CRLFTranslate bool
-	// TimeoutStuff int
+	NonBlockingRead bool
+	ReadTimeout     uint32
 }
 
 // OpenPort opens a serial port with the specified configuration
 func OpenPort(c *Config) (io.ReadWriteCloser, error) {
-	return openPort(c.Name, c.Baud)
+	return openPort(c.Name, c.Baud, c.NonBlockingRead, c.ReadTimeout)
 }
 
 // func Flush()

diff --git a/serial_linux.go b/serial_linux.go
@@ -9,7 +9,7 @@ import (
 	"unsafe"
 )
 
-func openPort(name string, baud int) (rwc io.ReadWriteCloser, err error) {
+func openPort(name string, baud int, nonBlockingRead bool, readTimeout uint32) (rwc io.ReadWriteCloser, err error) {
 
 	var bauds = map[int]uint32{
 		50:      syscall.B50,
@@ -62,10 +62,15 @@ func openPort(name string, baud int) (rwc io.ReadWriteCloser, err error) {
 	}()
 
 	fd := f.Fd()
+	// set blocking / non-blocking read
+	var minBytesToRead uint8 = 1
+	if nonBlockingRead == true {
+		minBytesToRead = 0
+	}
 	t := syscall.Termios{
 		Iflag:  syscall.IGNPAR,
 		Cflag:  syscall.CS8 | syscall.CREAD | syscall.CLOCAL | rate,
-		Cc:     [32]uint8{syscall.VMIN: 1},
+		Cc:     [32]uint8{syscall.VMIN: minBytesToRead, syscall.VTIME: uint8(readTimeout)},
 		Ispeed: rate,
 		Ospeed: rate,
 	}

diff --git a/serial_posix.go b/serial_posix.go
@@ -17,7 +17,7 @@ import (
 	//"unsafe"
 )
 
-func openPort(name string, baud int) (rwc io.ReadWriteCloser, err error) {
+func openPort(name string, baud int, nonBlockingRead bool, readTimeout uint32) (rwc io.ReadWriteCloser, err error) {
 	f, err := os.OpenFile(name, syscall.O_RDWR|syscall.O_NOCTTY|syscall.O_NONBLOCK, 0666)
 	if err != nil {
 		return
@@ -77,7 +77,19 @@ func openPort(name string, baud int) (rwc io.ReadWriteCloser, err error) {
 	// Select raw mode
 	st.c_lflag &= ^C.tcflag_t(C.ICANON | C.ECHO | C.ECHOE | C.ISIG)
 	st.c_oflag &= ^C.tcflag_t(C.OPOST)
-
+
+	// set blocking / non-blocking read
+	var minBytesToRead uint8 = 1	
+	if nonBlockingRead == true {
+		// EOF on zero read
+		minBytesToRead = 0
+	}
+	st.c_cc[C.VMIN] = C.cc_t(minBytesToRead)
+	st.c_cc[C.VTIME] = C.cc_t(readTimeout)
+
+	st.c_oflag &= ^C.tcflag_t(C.OPOST)
+	st.c_oflag &= ^C.tcflag_t(C.OPOST)
+
 	_, err = C.tcsetattr(fd, C.TCSANOW, &st)
 	if err != nil {
 		f.Close()

diff --git a/serial_windows.go b/serial_windows.go
@@ -37,7 +37,7 @@ type structTimeouts struct {
 	WriteTotalTimeoutConstant   uint32
 }
 
-func openPort(name string, baud int) (rwc io.ReadWriteCloser, err error) {
+func openPort(name string, baud int, nonBlockingRead bool, readTimeout uint32) (rwc io.ReadWriteCloser, err error) {
 	if len(name) > 0 && name[0] != '\\' {
 		name = "\\\\.\\" + name
 	}
@@ -65,7 +65,7 @@ func openPort(name string, baud int) (rwc io.ReadWriteCloser, err error) {
 	if err = setupComm(h, 64, 64); err != nil {
 		return
 	}
-	if err = setCommTimeouts(h); err != nil {
+	if err = setCommTimeouts(h, nonBlockingRead, readTimeout); err != nil {
 		return
 	}
 	if err = setCommMask(h); err != nil {
@@ -178,12 +178,18 @@ func setCommState(h syscall.Handle, baud int) error {
 	return nil
 }
 
-func setCommTimeouts(h syscall.Handle) error {
+func setCommTimeouts(h syscall.Handle, nonBlockingRead bool, readTimeout uint32) error {
 	var timeouts structTimeouts
 	const MAXDWORD = 1<<32 - 1
-	timeouts.ReadIntervalTimeout = MAXDWORD
-	timeouts.ReadTotalTimeoutMultiplier = MAXDWORD
-	timeouts.ReadTotalTimeoutConstant = MAXDWORD - 1
+	if nonBlockingRead == true {
+		timeouts.ReadIntervalTimeout = 1000
+		timeouts.ReadTotalTimeoutMultiplier = 0
+		timeouts.ReadTotalTimeoutConstant = readTimeout
+	} else {
+		timeouts.ReadIntervalTimeout = MAXDWORD
+		timeouts.ReadTotalTimeoutMultiplier = MAXDWORD
+		timeouts.ReadTotalTimeoutConstant = MAXDWORD - 1
+	}	
 
 	/* From http://msdn.microsoft.com/en-us/library/aa363190(v=VS.85).aspx