add stopbits parameter , add serial docs

utils/serial.go

@@ -12,13 +12,21 @@ var (
 	device     string
 	baudrate   int
 	bytesize   byte
+	stopbits   byte
 	port       *serial.Port
 	portOpened = false
 )
 
-func OpenPort(device string, baudrate int, bytesize byte) error {
-	log.Println("opening port device:", device, ", baudrate=", baudrate, ", bytesize=", bytesize)
-	config := &serial.Config{Name: device, Baud: baudrate, Size: bytesize, ReadTimeout: time.Second * 1}
+const readDuration = 500 * time.Millisecond
+
+// OpenPort open serial port
+func OpenPort(device string, baudrate int, bytesize byte, stopbits byte) error {
+	log.Println("opening port device:", device, ", baudrate=", baudrate, ", bytesize=", bytesize, "stopbits=", stopbits)
+	config := &serial.Config{Name: device,
+		Baud:        baudrate,
+		Size:        bytesize,
+		StopBits:    serial.StopBits(stopbits),
+		ReadTimeout: readDuration}
 	var err error
 	port, err = serial.OpenPort(config)
 	if err != nil {
@@ -30,6 +38,7 @@ func OpenPort(device string, baudrate int, bytesize byte) error {
 	return nil
 }
 
+//ReadPort read byte array from port
 func ReadPort() ([]byte, int) {
 	buffer := make([]byte, 256)
 	if !ServerRunning {
@@ -43,6 +52,7 @@ func ReadPort() ([]byte, int) {
 	return buffer, count
 }
 
+//IsPortOpen check serial port status
 func IsPortOpen() bool {
 	return portOpened
 }