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Communicting with an Arduino via COM Port / Serial Port

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I need to work with a small device(specifically an Arduino MicroController),

and communication between the PC and the MicroController is done via a Serial Port.

I need a way to Write and Read from the COM Port.

I searched the Forums for that, and found quite many threads about it.

Most of them mention a Solution by Martin, which uses an External DLL,

and a solution by DaleHolm, which again uses an external Library that needs to be installed.

My question:

Is there a chance that there's a solution,

that does not require installing a DLL on the machine?

I just need basic read+write from the COM Port..

Thank you very much


Edited by Zohar
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found this, hope it helps..

;- ComportStati.au3 --------------------------------------------- >>fst'12<< -
; - set/unset output statuslines (plus TxD) of serial port
; - read input statuslines of serial port
; - uses WinAPI only, no special DLLs, no extra UDFs
; - should work with native comport and serial-USB-Adapters
; - for AutoIt3 - www.autoitscript.com - www.autoit.de
;- V 20120402 --------------------------------- http://www.FrankSteinberg.de -

#include <ButtonConstants.au3>
#include <ComboConstants.au3>
#include <GUIConstantsEx.au3>
#include <StaticConstants.au3>
#include <WindowsConstants.au3>

;*** Build GUI:
Opt("GUIOnEventMode", 1)
#Region ### START Koda GUI section ### Form=C:\WinSpr\AutoIt\_Eigenes\COMStati.kxf
$Form1 = GUICreate(" ComportStati >>fst'12<<", 225, 211, -1, -1, $WS_SYSMENU)
GUISetOnEvent($GUI_EVENT_CLOSE, "Form1Close")
$Combo_Port = GUICtrlCreateCombo("No Port", 8, 8, 73, -1)
GUICtrlSetOnEvent(-1, "Combo_PortChange")
$Group_IN = GUICtrlCreateGroup(" IN ", 112, 40, 97, 113)
GUICtrlCreateGroup("", -99, -99, 1, 1)
$Check_TxD = GUICtrlCreateCheckbox(" TxD Pin 3", 16, 80, 80, 24)
GUICtrlSetOnEvent(-1, "Check_TxDClick")
$Check_DTR = GUICtrlCreateCheckbox(" DTR Pin 4", 16, 104, 80, 24)
GUICtrlSetOnEvent(-1, "Check_DTRClick")
$Check_RTS = GUICtrlCreateCheckbox(" RTS Pin 7", 16, 128, 80, 24)
GUICtrlSetOnEvent(-1, "Check_RTSClick")
$Group_OUT = GUICtrlCreateGroup(" OUT ", 8, 64, 97, 89)
GUICtrlCreateGroup("", -99, -99, 1, 1)
$Check_DCD = GUICtrlCreateCheckbox(" DCD Pin 1", 120, 56, 80, 24)
$Check_DSR = GUICtrlCreateCheckbox(" DSR Pin 6", 120, 80, 80, 24)
$Check_CTS = GUICtrlCreateCheckbox(" CTS Pin 8", 120, 104, 80, 24)
$Check_RI = GUICtrlCreateCheckbox(" RI Pin 9", 120, 128, 80, 24)
$Label_Info = GUICtrlCreateLabel("choose a COMport", 96, 12, 98, 17, 0)
$Label_URL = GUICtrlCreateLabel("www.FrankSteinberg.de", 47, 160, 118, 17, 0)
GUICtrlSetOnEvent(-1, "Label_URLClick")
GUICtrlSetColor(-1, 0x3399FF)
#EndRegion ### END Koda GUI section ###

;*** Declare global variables:
Global $hSerialPort[1] ;handle for seruial port
Global $lpModemStat ;pointer to status of serial input-lines
Global $sComboVal ;comport selected by user (combobox)
Global $sPortList ;list of all valid ports

;*** Create struct with one element to store input-line values - see Func Pin_Read():
$lpModemStat = DllStructCreate("DWORD")

;*** Main loop:
While 1
Port_Search() ;read valid ports from registry and add to combobox
Pin_Read() ;read status of comport input lines and show as checkboxes
Sleep(100) ;give some time to windows
;*** Main loop end

;*** Read valid ports from registry and add to combobox:
Func Port_Search() ;
$sPortListOld = $sPortList ;remember last values
$sPortList = "" ;delete last values
For $i = 1 To 256 ;max. possible comports = COM1 - COM256
Local $sRegVal = RegEnumVal("HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\SERIALCOMM\", $i) ;... all valid ports listed here
If @error <> 0 Then ExitLoop ;abort after last value
$sPortList = $sPortList & "|" & RegRead("HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\SERIALCOMM", $sRegVal) ;add value to list
If $sPortList = $sPortListOld Then Return ;exit func when no difference from last call
GUICtrlSetData($Combo_Port, $sPortList & "|close port") ;... otherwise replace list in combobox

;*** Open serial port using WinAPI:
Func Port_Open()
;** Open Port with 'CreateFile'; prefix '\\.\' adds support for Ports greater than COM9:
$hSerialPort = DllCall("kernel32.dll","hwnd","CreateFile","str","\\.\"&$sComboVal,"int",0xC0000000,"int",0,"ptr",0,"int",3,"int",0,"int",0)
GUICtrlSetData($Label_Info, $sComboVal & " open") ;write success-message to gui
If Number($hSerialPort[0]) < 1 Or @error Then ;if no success ...
GUICtrlSetData($Label_Info, "Com ERROR !") ;... write to gui
Return ;... and exit func
Check_DTRClick() ;switch DTR to current checkbox state
Check_RTSClick() ;switch RTS to current checkbox state
Check_TxDClick() ;switch TxD to current checkbox state

;*** Close serial Port:
Func Port_Close()
$hClose=DllCall("kernel32.dll", "int", "CloseHandle", "hwnd", $hSerialPort[0]) ;Win-API
If $hClose >= 0 Then GUICtrlSetData($Label_Info, "COM closed") ;write message to gui

;*** Read input-lines values and show as checkboxes:
Func Pin_Read()
;** Read stati of input-lines using WinAPI 'GetCommModemStatus':
DllCall("kernel32.dll", "long", "GetCommModemStatus", "HWND", $hSerialPort[0], "Ptr", DllStructGetPtr($lpModemStat))
$iPinState = DllStructGetData($lpModemStat, 1) ;all values are in $iPinState
;MsgBox(4096, String($lpModemStat), String($iPinState))
;Isolate value for CTS pin:
If BitAND($iPinState, 0x10) Then ;0x10 = MS_CTS_ON
GUICtrlSetState($Check_CTS, $GUI_CHECKED) ;set checbox, if bit is set
GUICtrlSetState($Check_CTS, $GUI_UNCHECKED) ;uncheck, if bit is unset
;Isolate value from DSR pin:
If BitAND($iPinState, 0x20) Then ;0x20 = MS_DSR_ON
GUICtrlSetState($Check_DSR, $GUI_CHECKED)
;Isolate value from RI pin:
If BitAND($iPinState, 0x40) Then ;0x40 = MS_RING_ON
GUICtrlSetState($Check_RI, $GUI_CHECKED)
GUICtrlSetState($Check_RI, $GUI_UNCHECKED)
;Isolate value from DCD pin:
If BitAND($iPinState, 0x80) Then ;0x80 = MS_RLSD_ON
GUICtrlSetState($Check_DCD, $GUI_CHECKED)

;*** Set/unset DTR pin using WinAPI 'EscapeCommFunction', when user clicks checkbox:
Func Check_DTRClick()
If GUICtrlRead($Check_DTR) = $GUI_CHECKED Then
DllCall("kernel32.dll","long","EscapeCommFunction","hwnd", $hSerialPort[0],"long", 5) ;5=SETDTR; set DTR high
DllCall("kernel32.dll","long","EscapeCommFunction","hwnd", $hSerialPort[0],"long", 6) ;6=CLRDTR; set DTR low

;*** Set/unset RTS pin using WinAPI 'EscapeCommFunction', when user clicks checkbox:
Func Check_RTSClick()
If GUICtrlRead($Check_RTS) = $GUI_CHECKED Then
DllCall("kernel32.dll","long","EscapeCommFunction","hwnd", $hSerialPort[0],"long", 3) ;3=SETRTS; set RTS high
DllCall("kernel32.dll","long","EscapeCommFunction","hwnd", $hSerialPort[0],"long", 4) ;4=CLRRTS; set RTS low

;*** Set/unset DTR pin using WinAPI 'EscapeCommFunction', when user clicks checkbox:
Func Check_TxDClick()
If GUICtrlRead($Check_TxD) = $GUI_CHECKED Then
DllCall("kernel32.dll","long","EscapeCommFunction","hwnd", $hSerialPort[0],"long", 8) ;8=SETBREAK; set TxD high (break)
DllCall("kernel32.dll","long","EscapeCommFunction","hwnd", $hSerialPort[0],"long", 9) ;9=CLRBREAK; set TxD low

;*** Open/close serial Port, depending on users clicks in combobox:
Func Combo_PortChange()
$sComboVal = GUICtrlRead($Combo_Port) ;read user value
Port_Close() ;close previous opened port
GUICtrlSetState($Check_TxD, $GUI_FOCUS) ;go to first checkbox
If GUICtrlRead($Combo_Port) = "close port" Then Return ;exit func, close-only is selected
Port_Open() ;open selected port

;*** Close port and exit app, when window is closed:
Func Form1Close()

;*** Show authors website on click on label:
Func Label_URLClick()
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Hi Torni

Thank you.

I think this code doesn't Send/Receive data via the COM Port,

but what it does, is tell if Data is flowing via the COM Port..

(that is, If I understood it correctly)


Thank you, it works!

And such a short code without all the DLLs and mess :)

Do you know how can I check if there's any waiting Data to be read?

(and also its Size, so I can then know how many Bytes to request to read..)

Also, do you have code for Writing too?

Thank you again!

Edited by Zohar
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I won't give the code since I'm not on my PC (using Android Tablet here), but remember these golden words:

'As you read (_WinAPI_ReadFile), so you shall you write (_WinAPI_WriteFile)'.

Good Luck with Arduino...


:bye: Hey there, was I helpful?


My Current OS: Win8 PRO (64-bit); Current AutoIt Version: v3.3.8.1

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:gathering: Perhaps, there could be some. But my brain is at its limit... for now, atleast Edited by MKISH


:bye: Hey there, was I helpful?


My Current OS: Win8 PRO (64-bit); Current AutoIt Version: v3.3.8.1

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