Added ability to just set or unset break condition

serial.go

@@ -54,6 +54,9 @@ type Port interface {
 
 	// Break sends a break for a determined time
 	Break(time.Duration) error
+
+	// Set or unset break condition, allows timing to be done more precisely outside of this module
+	SetBreak(bool) error
 }
 
 // NoTimeout should be used as a parameter to SetReadTimeout to disable timeout.

serial_unix.go

@@ -118,19 +118,36 @@ func (port *unixPort) Write(p []byte) (n int, err error) {
 }
 
 func (port *unixPort) Break(t time.Duration) error {
+	// set break
 	if err := unix.IoctlSetInt(port.handle, ioctlTiocsbrk, 0); err != nil {
 		return err
 	}
 
 	time.Sleep(t)
 
+	// clear break
 	if err := unix.IoctlSetInt(port.handle, ioctlTioccbrk, 0); err != nil {
 		return err
 	}
 
 	return nil
 }
 
+func (port *unixPort) SetBreak(setBreak bool) error {
+	if setBreak {
+		// set break
+		if err := unix.IoctlSetInt(port.handle, ioctlTiocsbrk, 0); err != nil {
+			return err
+		}
+	} else {
+		// clear break
+		if err := unix.IoctlSetInt(port.handle, ioctlTioccbrk, 0); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
 func (port *unixPort) SetMode(mode *Mode) error {
 	settings, err := port.getTermSettings()
 	if err != nil {

serial_windows.go

@@ -386,19 +386,37 @@ func (port *windowsPort) SetReadTimeout(timeout time.Duration) error {
 }
 
 func (port *windowsPort) Break(d time.Duration) error {
+	// set break
 	if err := setCommBreak(port.handle); err != nil {
 		return &PortError{causedBy: err}
 	}
 
 	time.Sleep(d)
 
+	// unset break
 	if err := clearCommBreak(port.handle); err != nil {
 		return &PortError{causedBy: err}
 	}
 
 	return nil
 }
 
+func (port *windowsPort) SetBreak(setBreak bool) error {
+	if setBreak {
+		// set break
+		if err := setCommBreak(port.handle); err != nil {
+			return &PortError{causedBy: err}
+		}
+	} else {
+		// unset break
+		if err := clearCommBreak(port.handle); err != nil {
+			return &PortError{causedBy: err}
+		}
+	}
+
+	return nil
+}
+
 func createOverlappedEvent() (*syscall.Overlapped, error) {
 	h, err := createEvent(nil, true, false, nil)
 	return &syscall.Overlapped{HEvent: h}, err