Allow same serial port to be used as input and output

Makefile

@@ -4,7 +4,7 @@ BUILD_FOLDER=build
 BINARY=${BUILD_FOLDER}/nmea_ugps
 
 # Pass variables for version number, sha id and build number
-VERSION=1.1.0
+VERSION=1.1.1
 SHA=$(shell git rev-parse --short HEAD)
 # Set fallback build num if not set by environment variable
 BUILDNUM?=local

in.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"log"
 	"net"
-	"os"
 	"strconv"
 	"strings"
 	"time"
@@ -115,18 +114,7 @@ func inputUDPLoop(listen string, msg chan externalMaster, inStatsCh chan inputSt
 	}
 }
 
-func inputSerialLoop(port string, baudrate int, msg chan externalMaster, inStatsCh chan inputStats) {
-	if baudrate == 0 {
-		baudrate = 112500
-	}
-
-	c := &serial.Config{Name: port, Baud: baudrate}
-	s, err := serial.OpenPort(c)
-	if err != nil {
-		fmt.Printf("Error opening serial port: %v\n", err)
-		os.Exit(1)
-	}
-	defer s.Close()
+func inputSerialLoop(s *serial.Port, msg chan externalMaster, inStatsCh chan inputStats) {
 
 	scanner := bufio.NewReader(s)
 	for {
@@ -153,29 +141,7 @@ func inputSerialLoop(port string, baudrate int, msg chan externalMaster, inStats
 	}
 }
 
-func inputLoop(listen string, inputStatusCh chan inputStats) {
-	masterCh := make(chan externalMaster, 1)
-
-	// Use ":" to decide if this is UDP address or serial device
-	if len(strings.Split(listen, ":")) > 1 {
-		// Start listening on UDP
-		go inputUDPLoop(listen, masterCh, inputStatusCh)
-	} else {
-		baudrate := 0
-		// Is the baudrate specified?
-		parts := strings.Split(listen, "@")
-		if len(parts) > 1 {
-			b, err := strconv.Atoi(parts[1])
-			if err != nil {
-				fmt.Printf("Unable to parse baudrate: %s as numeric value\n", parts[1])
-				os.Exit(1)
-			}
-			baudrate = b
-			listen = parts[0]
-		}
-		// Start listening on serial port
-		go inputSerialLoop(listen, baudrate, masterCh, inputStatusCh)
-	}
+func inputLoop(masterCh chan externalMaster, inputStatusCh chan inputStats) {
 
 	for {
 		select {

main.go

@@ -3,11 +3,17 @@ package main
 import (
 	"flag"
 	"fmt"
+	"io"
 	"log"
+	"net"
+	"os"
+	"strconv"
+	"strings"
 	"time"
 
 	ui "github.com/gizak/termui/v3"
 	"github.com/gizak/termui/v3/widgets"
+	"github.com/tarm/serial"
 )
 
 var (
@@ -26,21 +32,109 @@ func debugPrintf(arguments string, a ...interface{}) {
 	}
 }
 
+// deviceIsUDP uses ":" to decide if this is UDP address or serial device
+func deviceIsUDP(device string) bool {
+	return len(strings.Split(listen, ":")) > 1
+}
+
+func baudAndPortFromDevice(device string) (string, int) {
+	baudrate := 115200
+	port := device
+	// Is the baudrate specified?
+	parts := strings.Split(device, "@")
+	if len(parts) > 1 {
+		b, err := strconv.Atoi(parts[1])
+		if err != nil {
+			fmt.Printf("Unable to parse baudrate: %s as numeric value\n", parts[1])
+			os.Exit(1)
+		}
+		baudrate = b
+		port = parts[0]
+	}
+	return port, baudrate
+}
+
 func main() {
 	fmt.Printf("Water Linked NMEA UGPS bridge (v%s %s.%s)\n", Version, BuildNum, SHA)
 	flag.StringVar(&listen, "i", "0.0.0.0:7777", "UDP device and port (host:port) OR serial device (COM7 /dev/ttyUSB1@4800) to listen for NMEA input. ")
-	flag.StringVar(&output, "o", "127.0.0.1:2947", "UDP device and port (host:port) OR serial device (COM7 /dev/ttyUSB1) to send NMEA output. ")
+	flag.StringVar(&output, "o", "", "UDP device and port (host:port) OR serial device (COM7 /dev/ttyUSB1) to send NMEA output. ")
 	flag.StringVar(&baseURL, "url", "http://192.168.2.94", "URL of Underwater GPS")
 	//flag.BoolVar(&verbose, "v", false, "verbose")
 	flag.Parse()
 
+	// Same serial port for input and output?
+	sameInOut := (listen == output) && !deviceIsUDP(listen)
+	if sameInOut {
+		fmt.Println("Same port for input and output", listen)
+	}
+
+	// Channels
 	inStatusCh := make(chan inputStats, 1)
-	go inputLoop(listen, inStatusCh)
+	masterCh := make(chan externalMaster, 1)
 	outStatusCh := make(chan outStats, 1)
-	if output != "" {
-		go outputLoop(output, outStatusCh)
+
+	// Output
+	var writer io.Writer = nil
+
+	// Setup input
+	if deviceIsUDP(listen) {
+		// Input from UDP
+		go inputUDPLoop(listen, masterCh, inStatusCh)
+	} else {
+		// Input from serial port
+		port, baudrate := baudAndPortFromDevice(listen)
+
+		c := &serial.Config{Name: port, Baud: baudrate}
+		s, err := serial.OpenPort(c)
+		if err != nil {
+			fmt.Printf("Error opening serial port: %v\n", err)
+			os.Exit(1)
+		}
+		defer s.Close()
+
+		go inputSerialLoop(s, masterCh, inStatusCh)
+		if sameInOut {
+			// Output is to same serial port as input
+			writer = s
+		}
+	}
+	go inputLoop(masterCh, inStatusCh)
+
+	// Setup output
+	if output == "" {
+		// Output disabled
+	} else if deviceIsUDP(output) {
+		// Output to UDP
+		conn, err := net.Dial("udp", output)
+		if err != nil {
+			fmt.Printf("Error connecting to UDP: %v\n", err)
+			os.Exit(1)
+		}
+		defer conn.Close()
+		writer = conn
+
+	} else if !sameInOut {
+		// Output to different serial port
+		port, baudrate := baudAndPortFromDevice(listen)
+
+		c := &serial.Config{Name: port, Baud: baudrate}
+		s, err := serial.OpenPort(c)
+		if err != nil {
+			fmt.Printf("Error opening serial port: %v\n", err)
+			os.Exit(1)
+		}
+		defer s.Close()
+		writer = s
+	}
+
+	if writer != nil {
+		go outputLoop(writer, outStatusCh)
 	}
 
+	RunUI(inStatusCh, outStatusCh)
+}
+
+func RunUI(inStatusCh chan inputStats, outStatusCh chan outStats) {
 	// Let the goroutines initialize before starting GUI
 	time.Sleep(50 * time.Millisecond)
 	if err := ui.Init(); err != nil {
@@ -71,6 +165,9 @@ func main() {
 	outStatus := widgets.NewParagraph()
 	outStatus.Title = "Output status"
 	outStatus.Text = "Waiting for data"
+	if output == "" {
+		outStatus.Text = "Output not enabled"
+	}
 	height = 10
 	outStatus.SetRect(0, y, 80, y+height)
 	y += height
@@ -81,6 +178,9 @@ func main() {
 		ui.Render(p, inpStatus, outStatus)
 	}
 
+	// Intial draw before any events have occured
+	draw()
+
 	uiEvents := ui.PollEvents()
 
 	for {

out.go

@@ -4,14 +4,9 @@ import (
 	"fmt"
 	"io"
 	"math"
-	"net"
-	"os"
-	"strconv"
-	"strings"
 	"time"
 
 	"github.com/pilebones/go-nmea"
-	"github.com/tarm/serial"
 )
 
 type outStats struct {
@@ -24,48 +19,12 @@ type outStats struct {
 
 const updateSeconds = 10
 
-func outputLoop(output string, outStatusCh chan outStats) {
+func outputLoop(writer io.Writer, outStatusCh chan outStats) {
 	var prevLat float64
 	var prevLon float64
 
 	var stats outStats
 
-	var writer io.Writer
-
-	// Use ":" to decide if this is UDP address or serial device
-	if len(strings.Split(output, ":")) > 1 {
-		conn, err := net.Dial("udp", output)
-		if err != nil {
-			fmt.Printf("Error connecting to UDP: %v\n", err)
-			os.Exit(1)
-		}
-		defer conn.Close()
-		writer = conn
-
-	} else {
-		baudrate := 115200
-		port := output
-		// Is the baudrate specified?
-		parts := strings.Split(output, "@")
-		if len(parts) > 1 {
-			b, err := strconv.Atoi(parts[1])
-			if err != nil {
-				fmt.Printf("Unable to parse baudrate: %s as numeric value\n", parts[1])
-				os.Exit(1)
-			}
-			baudrate = b
-			port = parts[0]
-		}
-		c := &serial.Config{Name: port, Baud: baudrate}
-		s, err := serial.OpenPort(c)
-		if err != nil {
-			fmt.Printf("Error opening serial port: %v\n", err)
-			os.Exit(1)
-		}
-		defer s.Close()
-		writer = s
-	}
-
 	for {
 		time.Sleep(100 * time.Millisecond)
 		pos, err := getGlobalPosition()