diff --git a/go.mod b/go.mod
index 4544601..9da1151 100644
--- a/go.mod
+++ b/go.mod
@@ -1,7 +1,3 @@
 module github.com/robinson/gos7
 
-go 1.21.1
-
-require github.com/tarm/serial v0.0.0-20180830185346-98f6abe2eb07
-
-require golang.org/x/sys v0.12.0 // indirect
+go 1.21
diff --git a/go.sum b/go.sum
index b36cffd..e69de29 100644
--- a/go.sum
+++ b/go.sum
@@ -1,4 +0,0 @@
-github.com/tarm/serial v0.0.0-20180830185346-98f6abe2eb07 h1:UyzmZLoiDWMRywV4DUYb9Fbt8uiOSooupjTq10vpvnU=
-github.com/tarm/serial v0.0.0-20180830185346-98f6abe2eb07/go.mod h1:kDXzergiv9cbyO7IOYJZWg1U88JhDg3PB6klq9Hg2pA=
-golang.org/x/sys v0.12.0 h1:CM0HF96J0hcLAwsHPJZjfdNzs0gftsLfgKt57wWHJ0o=
-golang.org/x/sys v0.12.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
diff --git a/serial.go b/serial.go
deleted file mode 100644
index ffbdd6c..0000000
--- a/serial.go
+++ /dev/null
@@ -1,105 +0,0 @@
-package gos7
-
-// Copyright 2018 Trung Hieu Le. All rights reserved.
-// This software may be modified and distributed under the terms
-// of the BSD license. See the LICENSE file for details.
-
-//tarm serial from https://github.com/tarm/serial
-//godoc: https://godoc.org/github.com/tarm/serial
-
-import (
-	"io"
-	"log"
-	"sync"
-	"time"
-
-	"github.com/tarm/serial"
-)
-
-const (
-	// Default timeout
-	serialTimeout     = 5 * time.Second
-	serialIdleTimeout = 60 * time.Second
-)
-
-// serialPort has configuration and I/O controller.
-type serialPort struct {
-	// Serial port configuration.
-	serial.Config
-
-	Logger      *log.Logger
-	IdleTimeout time.Duration
-
-	mu sync.Mutex
-	// port is platform-dependent data structure for serial port.
-	port         io.ReadWriteCloser
-	lastActivity time.Time
-	closeTimer   *time.Timer
-}
-
-func (mb *serialPort) Connect() (err error) {
-	mb.mu.Lock()
-	defer mb.mu.Unlock()
-
-	return mb.connect()
-}
-
-// connect connects to the serial port if it is not connected. Caller must hold the mutex.
-func (mb *serialPort) connect() error {
-	if mb.port == nil {
-		port, err := serial.OpenPort(&mb.Config)
-		if err != nil {
-			return err
-		}
-		mb.port = port
-	}
-	return nil
-}
-
-func (mb *serialPort) Close() (err error) {
-	mb.mu.Lock()
-	defer mb.mu.Unlock()
-
-	return mb.close()
-}
-
-// close closes the serial port if it is connected. Caller must hold the mutex.
-func (mb *serialPort) close() (err error) {
-	if mb.port != nil {
-		err = mb.port.Close()
-		mb.port = nil
-	}
-	return
-}
-
-func (mb *serialPort) logf(format string, v ...interface{}) {
-	if mb.Logger != nil {
-		mb.Logger.Printf(format, v...)
-	}
-}
-
-func (mb *serialPort) startCloseTimer() {
-	if mb.IdleTimeout <= 0 {
-		return
-	}
-	if mb.closeTimer == nil {
-		mb.closeTimer = time.AfterFunc(mb.IdleTimeout, mb.closeIdle)
-	} else {
-		mb.closeTimer.Reset(mb.IdleTimeout)
-	}
-}
-
-// closeIdle closes the connection if last activity is passed behind IdleTimeout.
-func (mb *serialPort) closeIdle() {
-	mb.mu.Lock()
-	defer mb.mu.Unlock()
-
-	if mb.IdleTimeout <= 0 {
-		return
-	}
-	idle := time.Now().Sub(mb.lastActivity)
-	if idle >= mb.IdleTimeout {
-		mb.logf("modbus: closing connection due to idle timeout: %v", idle)
-		mb.close()
-	}
-}
diff --git a/serial_test.go b/serial_test.go
deleted file mode 100644
index 6307606..0000000
--- a/serial_test.go
+++ /dev/null
@@ -1,36 +0,0 @@
-package gos7
-
-import (
-	"bytes"
-	"io"
-	"testing"
-	"time"
-)
-
-type nopCloser struct {
-	io.ReadWriter
-
-	closed bool
-}
-
-func (n *nopCloser) Close() error {
-	n.closed = true
-	return nil
-}
-
-func TestSerialCloseIdle(t *testing.T) {
-	port := &nopCloser{
-		ReadWriter: &bytes.Buffer{},
-	}
-	s := serialPort{
-		port:        port,
-		IdleTimeout: 100 * time.Millisecond,
-	}
-	s.lastActivity = time.Now()
-	s.startCloseTimer()
-
-	time.Sleep(150 * time.Millisecond)
-	if !port.closed || s.port != nil {
-		t.Fatalf("serial port is not closed when inactivity: %+v", port)
-	}
-}