diff --git a/firmware/firmware.go b/firmware/firmware.go
new file mode 100644
index 0000000..a68d985
--- /dev/null
+++ b/firmware/firmware.go
@@ -0,0 +1,77 @@
+package firmware
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"hash/crc32"
+	"io"
+	"io/ioutil"
+	"os"
+	"path"
+)
+
+// FwExists  check if file exists
+func FwExists(path string) bool {
+	_, err := os.Stat(path)
+	return !errors.Is(err, os.ErrNotExist)
+}
+
+func ChkHeader(fwfile string) bool {
+	fmt.Println("checking ", fwfile)
+	// SCS has two different file layouts, one for the "Dragons", the other for any older modem
+	var offset uint32
+	if path.Ext(fwfile) == ".dr7" {
+		offset = 0
+	} else {
+		offset = 4
+	}
+	r, err := os.Open(fwfile)
+	if err != nil {
+		return false
+	}
+	defer r.Close()
+
+	var header [2]byte
+	_, err = io.ReadFull(r, header[:])
+	if err != nil {
+		return false
+	}
+
+	if offset == 0 {
+		if header != [2]byte{0x50, 0x34} {
+			fmt.Println("ERROR: wrong firmware header")
+			//return false
+		}
+	} else {
+		if header != [2]byte{0x60, 0xea} {
+			fmt.Println("ERROR: wrong firmware header")
+			//return false
+		}
+	}
+
+	r.Close()
+	firmware, err := ioutil.ReadFile(fwfile)
+	if err != nil {
+		fmt.Println("ERROR: ReadFile operation failed")
+	}
+
+	var size uint32
+	if offset == 0 {
+		size = binary.LittleEndian.Uint32(firmware[4:8]) // Dragons
+	} else {
+		size = uint32(binary.LittleEndian.Uint16(firmware[2:4])) // PTC-3 and Co
+	}
+	a := make([]byte, 4)
+	//binary.LittleEndian.PutUint32(a, crc32.ChecksumIEEE(firmware[4:size+4])) // PTC-3
+	binary.LittleEndian.PutUint32(a, crc32.ChecksumIEEE(firmware[offset:offset+size]))
+	//if bytes.Equal(a, firmware[4+size:8+size]) { // PTC-3
+	if bytes.Equal(a, firmware[offset+size:offset+size+4]) {
+		fmt.Println("CRC checksum ok!")
+	} else {
+		fmt.Println("CRC checksum NOT ok!")
+		return false
+	}
+	return true
+}
diff --git a/go.mod b/go.mod
index 97dfee2..3c4a292 100644
--- a/go.mod
+++ b/go.mod
@@ -2,10 +2,16 @@ module go-scsupdate
 
 go 1.17
 
-require github.com/albenik/go-serial v1.2.0
+require (
+	github.com/akamensky/argparse v1.3.1
+	github.com/albenik/go-serial v1.2.0
+)
 
 require (
 	github.com/creack/goselect v0.1.0 // indirect
+	github.com/sigurn/crc16 v0.0.0-20211026045750-20ab5afb07e3 // indirect
+	github.com/sigurn/crc8 v0.0.0-20160107002456-e55481d6f45c // indirect
+	github.com/sigurn/utils v0.0.0-20190728110027-e1fefb11a144 // indirect
 	go.uber.org/atomic v1.4.0 // indirect
 	go.uber.org/multierr v1.1.0 // indirect
 	golang.org/x/sys v0.0.0-20190712062909-fae7ac547cb7 // indirect
diff --git a/go.sum b/go.sum
index 17a385b..4f6d2d8 100644
--- a/go.sum
+++ b/go.sum
@@ -1,3 +1,5 @@
+github.com/akamensky/argparse v1.3.1 h1:kP6+OyvR0fuBH6UhbE6yh/nskrDEIQgEA1SUXDPjx4g=
+github.com/akamensky/argparse v1.3.1/go.mod h1:S5kwC7IuDcEr5VeXtGPRVZ5o/FdhcMlQz4IZQuw64xA=
 github.com/albenik/go-serial v1.2.0 h1:VhEIWqP5tbWtsWoCjeBHHQEf6qeXpsJXvZBP9px5F84=
 github.com/albenik/go-serial v1.2.0/go.mod h1:9NHUOwCBJER+lAaitTWLJda/GnYoP4Vga7KU3vn1lmM=
 github.com/creack/goselect v0.1.0 h1:4QiXIhcpSQF50XGaBsFzesjwX/1qOY5bOveQPmN9CXY=
@@ -7,6 +9,12 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/sigurn/crc16 v0.0.0-20211026045750-20ab5afb07e3 h1:aQKxg3+2p+IFXXg97McgDGT5zcMrQoi0EICZs8Pgchs=
+github.com/sigurn/crc16 v0.0.0-20211026045750-20ab5afb07e3/go.mod h1:9/etS5gpQq9BJsJMWg1wpLbfuSnkm8dPF6FdW2JXVhA=
+github.com/sigurn/crc8 v0.0.0-20160107002456-e55481d6f45c h1:hk0Jigjfq59yDMgd6bzi22Das5tyxU0CtOkh7a9io84=
+github.com/sigurn/crc8 v0.0.0-20160107002456-e55481d6f45c/go.mod h1:cyrWuItcOVIGX6fBZ/G00z4ykprWM7hH58fSavNkjRg=
+github.com/sigurn/utils v0.0.0-20190728110027-e1fefb11a144 h1:ccb8W1+mYuZvlpn/mJUMAbsFHTMCpcJBS78AsBQxNcY=
+github.com/sigurn/utils v0.0.0-20190728110027-e1fefb11a144/go.mod h1:VRI4lXkrUH5Cygl6mbG1BRUfMMoT2o8BkrtBDUAm+GU=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0Q=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
diff --git a/main.go b/main.go
index c46fc26..2168cb3 100644
--- a/main.go
+++ b/main.go
@@ -1,5 +1,51 @@
 package main
 
+import (
+	"fmt"
+	"github.com/akamensky/argparse"
+	"go-scsupdate/firmware"
+	"go-scsupdate/usb"
+	"os"
+)
+
 func main() {
-	lsusb()
+	parser := argparse.NewParser("go-scsupdate", "Update Firmware of SCS PACTOR modems")
+	serialDevice := parser.String("s", "serialDevice", &argparse.Options{Required: false, Help: "(optional) serial device the modem is attached to, e.g. /dev/ttyUSB0. If not set, go-scsupdate will search for SCS modems."})
+	_ = parser.String("b", "baudrate", &argparse.Options{Required: false, Help: "(optional) sets the serial baudrate, e.g. 115200"})
+	f := parser.String("f", "file", &argparse.Options{Required: false, Help: "(required) the file to flash, e.g. profi41r.pro"})
+	err := parser.Parse(os.Args)
+	if err != nil {
+		fmt.Print(parser.Usage(err))
+		os.Exit(1)
+	}
+	fmt.Println(*serialDevice)
+	var ports []usb.Scsid
+	if *serialDevice == "" {
+		if ports, err = usb.FindSCS(); err == nil {
+			fmt.Println(ports)
+			if len(ports) == 0 {
+				fmt.Println("Found no SCS modem.")
+				//os.Exit(1)
+			}
+			if len(ports) != 1 {
+				fmt.Println("Found more than one SCS modem. You need to choose one with the -s flag.\nfound: ")
+				for _, p := range ports {
+					fmt.Printf("Port: %30s : Name: %s\n", p.Port, p.Name)
+				}
+			}
+		} else {
+			fmt.Println("Error while seaching SCS modems: ", err)
+		}
+	}
+
+	if !firmware.FwExists(*f) {
+		fmt.Printf("Error: firmware file %s does not exist.\n", *f)
+		os.Exit(1)
+	}
+
+	if !firmware.ChkHeader(*f) {
+		os.Exit(1)
+	} else {
+		fmt.Println("all ok")
+	}
 }
diff --git a/usb.go b/usb.go
deleted file mode 100644
index 4532a3a..0000000
--- a/usb.go
+++ /dev/null
@@ -1,39 +0,0 @@
-package main
-
-import (
-	"fmt"
-	"log"
-
-	"github.com/albenik/go-serial/enumerator"
-)
-
-/*
- USB Product IDs of the SCS devices:
-    0xD010 SCS PTC-IIusb
-    0xD011 SCS Tracker / DSP TNC
-    0xD012 SCS P4dragon DR-7800
-    0xD013 SCS P4dragon DR-7400
-    0xD014 - not used
-    0xD015 SCS PTC-IIIusb
-    0xD016 - not used
-    0xD017 - not used
-*/
-
-func lsusb() {
-	ports, err := enumerator.GetDetailedPortsList()
-	if err != nil {
-		log.Fatal(err)
-	}
-	if len(ports) == 0 {
-		fmt.Println("No serial ports found!")
-		return
-	}
-	for _, port := range ports {
-		fmt.Printf("Found port: %s\n", port.Name)
-		if port.IsUSB {
-			fmt.Printf("   USB ID     %s:%s\n", port.VID, port.PID)
-			fmt.Printf("   USB serial %s\n", port.SerialNumber)
-		}
-	}
-
-}
diff --git a/usb/usb.go b/usb/usb.go
new file mode 100644
index 0000000..a0bda1c
--- /dev/null
+++ b/usb/usb.go
@@ -0,0 +1,67 @@
+package usb
+
+import (
+	"errors"
+	"fmt"
+	"github.com/albenik/go-serial/enumerator"
+	"log"
+)
+
+/*
+ USB Product IDs of the SCS devices:
+    0xD010 SCS PTC-IIusb
+    0xD011 SCS Tracker / DSP TNC
+    0xD012 SCS P4dragon DR-7800
+    0xD013 SCS P4dragon DR-7400
+    0xD014 - not used
+    0xD015 SCS PTC-IIIusb
+    0xD016 - not used
+    0xD017 - not used
+*/
+
+type Scsid struct {
+	Port, id, Name string
+	Baudrate       int
+}
+
+var scsids map[string]string = map[string]string{
+	"d010": "SCS PTC-IIusb",
+	"d011": "SCS Tracker / DSP TNC",
+	"d012": "SCS P4dragon DR-7800",
+	"d013": "SCS P4dragon DR-7400",
+	"d015": "SCS PTC-IIIusb"}
+
+var scsbaudrates map[string]int = map[string]int{
+	"d010": 115200,
+	"d011": 38400,
+	"d012": 829400,
+	"d013": 829400,
+	"d015": 115200}
+
+func FindSCS() ([]Scsid, error) {
+
+	foundids := []Scsid{}
+	ports, err := enumerator.GetDetailedPortsList()
+	if err != nil {
+		log.Fatal(err)
+		return nil, err
+	}
+	if len(ports) == 0 {
+		return nil, errors.New("No serial ports found")
+	}
+
+	for _, port := range ports {
+		fmt.Printf("Found Port: %s\n", port.Name)
+		if port.IsUSB {
+			// fmt.Printf("   USB ID     %s:%s\n", Port.VID, Port.PID)
+			// fmt.Printf("   USB serial %s\n", Port.SerialNumber)
+			if port.VID == "0403" {
+				if _, ok := scsids[port.PID]; ok {
+					foundids = append(foundids, Scsid{Port: port.Name, id: port.PID, Name: scsids[port.PID], Baudrate: scsbaudrates[port.PID]})
+				}
+			}
+		}
+	}
+	return foundids, nil
+
+}