fix a panic when the serial port is busy

Author: alessio-perugini

main.go

@@ -7,12 +7,12 @@ import (
 	"log"
 	"time"
 
-	"github.com/arduino/arduino-cli/arduino/serialutils"
 	"github.com/arduino/arduino-cli/executils"
 	helper "github.com/arduino/fwuploader-plugin-helper"
 	"github.com/arduino/go-paths-helper"
 	"github.com/arduino/uno-r4-wifi-fwuploader-plugin/certificate"
 	"github.com/arduino/uno-r4-wifi-fwuploader-plugin/serial"
+	serialutils "github.com/arduino/uno-r4-wifi-fwuploader-plugin/serial/utils"
 	semver "go.bug.st/relaxed-semver"
 	serialx "go.bug.st/serial"
 	"golang.org/x/exp/slog"
@@ -215,7 +215,7 @@ func (p *unoR4WifiPlugin) uploadCommandsSketch(portAddress string, feedback *hel
 	defer rebootFile.Remove()
 
 	slog.Info("sending serial reset")
-	if _, err = serialutils.Reset(portAddress, false, nil, false); err != nil {
+	if err := serialutils.TouchSerialPortAt1200bps(portAddress); err != nil {
 		return err
 	}
 

serial/utils/utils.go

@@ -0,0 +1,44 @@
+// Those function are token from https://github.com/arduino/arduino-cli/blob/master/arduino/serialutils/serialutils.go
+// that's because we don't have the `tr` here and importing the serialutils from the cli will lead to a panic
+package utils
+
+import (
+	"fmt"
+	"runtime"
+	"time"
+
+	"go.bug.st/serial"
+)
+
+// TouchSerialPortAt1200bps open and close the serial port at 1200 bps. This
+// is used on many Arduino boards as a signal to put the board in "bootloader"
+// mode.
+func TouchSerialPortAt1200bps(port string) error {
+	// Open port
+	p, err := serial.Open(port, &serial.Mode{BaudRate: 1200})
+	if err != nil {
+		return fmt.Errorf("opening port at 1200bps")
+	}
+
+	if runtime.GOOS != "windows" {
+		// This is not required on Windows
+		// TODO: Investigate if it can be removed for other OS too
+
+		// Set DTR to false
+		if err = p.SetDTR(false); err != nil {
+			p.Close()
+			return fmt.Errorf("setting DTR to OFF")
+		}
+	}
+
+	// Close serial port
+	p.Close()
+
+	// Scanning for available ports seems to open the port or
+	// otherwise assert DTR, which would cancel the WDT reset if
+	// it happens within 250 ms. So we wait until the reset should
+	// have already occurred before going on.
+	time.Sleep(500 * time.Millisecond)
+
+	return nil
+}