main: add serial port monitoring functionality

Co-authored-by: Ayke <aykevanlaethem@gmail.com>

monitor.go

@@ -0,0 +1,101 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"os/signal"
+	"time"
+
+	"github.com/mattn/go-tty"
+	"github.com/tinygo-org/tinygo/builder"
+	"github.com/tinygo-org/tinygo/compileopts"
+	"go.bug.st/serial"
+)
+
+// Monitor connects to the given port and reads/writes the serial port.
+func Monitor(port string, options *compileopts.Options) error {
+	config, err := builder.NewConfig(options)
+	if err != nil {
+		return err
+	}
+
+	wait := 300
+	for i := 0; i <= wait; i++ {
+		port, err = getDefaultPort(port, config.Target.SerialPort)
+		if err != nil {
+			if i < wait {
+				time.Sleep(10 * time.Millisecond)
+				continue
+			}
+			return err
+		}
+		break
+	}
+
+	wait = 300
+	var p serial.Port
+	for i := 0; i <= wait; i++ {
+		p, err = serial.Open(port, &serial.Mode{})
+		if err != nil {
+			if i < wait {
+				time.Sleep(10 * time.Millisecond)
+				continue
+			}
+			return err
+		}
+		break
+	}
+	defer p.Close()
+
+	tty, err := tty.Open()
+	if err != nil {
+		return err
+	}
+	defer tty.Close()
+
+	sig := make(chan os.Signal, 1)
+	signal.Notify(sig, os.Interrupt)
+	defer signal.Stop(sig)
+
+	go func() {
+		<-sig
+		tty.Close()
+		os.Exit(0)
+	}()
+
+	fmt.Printf("Connected to %s. Press Ctrl-C to exit.\n", port)
+
+	errCh := make(chan error, 1)
+
+	go func() {
+		buf := make([]byte, 100*1024)
+		for {
+			n, err := p.Read(buf)
+			if err != nil {
+				errCh <- fmt.Errorf("read error: %w", err)
+				return
+			}
+
+			if n == 0 {
+				continue
+			}
+			fmt.Printf("%v", string(buf[:n]))
+		}
+	}()
+
+	go func() {
+		for {
+			r, err := tty.ReadRune()
+			if err != nil {
+				errCh <- err
+				return
+			}
+			if r == 0 {
+				continue
+			}
+			p.Write([]byte(string(r)))
+		}
+	}()
+
+	return <-errCh
+}