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POHow to detect addition of new serial port?
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copied!<p>To communicate with micro controllers I use the serial port. I use TCommPortDriver 2.1 which works fine. However, it lacks the ability to detect the addition or removal of new comports. This happens regularly during a session.</p> <p>Is there an event that tells when a comport has been added or removed?</p> <p><strong>Update 1</strong></p> <p>I tried the first suggestion of RRUZ and turned it into a standalone program. It reacts on a <code>WM_DEVICECHANGE</code> when the cable is plugged in or out, but <code>WParam</code> does not show arrival or removal of the device. Results are:</p> <pre><code>msg = 537, wparam = 7, lparam = 0 msg = 537, wparam = 7, lparam = 0 msg = 537, wparam = 7, lparam = 0 </code></pre> <p>The first message is sent when the USB cable is plugged out and the next two when it is plugged in. The message part shows the <code>WM_DEVICECHANGE</code> message (537) but <code>WParam</code> is 7, which is not <code>WM_DEVICECHANGE</code> or <code>DBT_DEVICEARRIVAL</code>. I modified the code somewhat in order the message to be processed but as <code>LParam</code> is zero this is no use. Results are identical to VCL and FMX. As a check see code below.</p> <p><strong>Update 2</strong></p> <p>I now got the WMI code running. It only fires when a COM port is added, no reaction when one is removed. Results:</p> <pre><code>TargetInstance.ClassGuid : {4d36e978-e325-11ce-bfc1-08002be10318} TargetInstance.Description : Arduino Mega ADK R3 TargetInstance.Name : Arduino Mega ADK R3 (COM4) TargetInstance.PNPDeviceID : USB\VID_2341&PID_0044\64935343733351E0E1D1 TargetInstance.Status : OK </code></pre> <p>Might this explain the fact that in the other code this is not seen as the addition of a COM port? It appears to see the new connection as a USB port (what it actually is). The Arduino driver translates this into a COM port but that is not recognized by WMI. Windows messaging 'sees' a COM port change but cannot detect whether it is added or removed.</p> <p>Anyhow: the device change works. I only need to enumerate the COM ports to see which one are actually present and that was something I already did manually. Now I can do that automatically with <code>WM_DEVICECHANGE</code>. I just add an event to the CPDrv component.</p> <p>Thanks RRUZ for your code and help!</p> <pre><code> unit dev_change; interface uses Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics, Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls; type TProc = procedure (text: string) of object; BroadcastHdr = ^DEV_BROADCAST_HDR; DEV_BROADCAST_HDR = packed record dbch_size: DWORD; dbch_devicetype: DWORD; dbch_reserved: DWORD; end; TDevBroadcastHdr = DEV_BROADCAST_HDR; type PDevBroadcastDeviceInterface = ^DEV_BROADCAST_DEVICEINTERFACE; DEV_BROADCAST_DEVICEINTERFACE = record dbcc_size: DWORD; dbcc_devicetype: DWORD; dbcc_reserved: DWORD; dbcc_classguid: TGUID; dbcc_name: Char; end; TDevBroadcastDeviceInterface = DEV_BROADCAST_DEVICEINTERFACE; const DBT_DEVICESOMETHING = $0007; DBT_DEVICEARRIVAL = $8000; DBT_DEVICEREMOVECOMPLETE = $8004; DBT_DEVTYP_DEVICEINTERFACE = $00000005; type TDeviceNotifyProc = procedure(Sender: TObject; const DeviceName: String) of Object; TDeviceNotifier = class private hRecipient: HWND; FNotificationHandle: Pointer; FDeviceArrival: TDeviceNotifyProc; FDeviceRemoval: TDeviceNotifyProc; FOnWin: TProc; procedure WndProc(var Msg: TMessage); public constructor Create(GUID_DEVINTERFACE : TGUID); property OnDeviceArrival: TDeviceNotifyProc read FDeviceArrival write FDeviceArrival; property OnDeviceRemoval: TDeviceNotifyProc read FDeviceRemoval write FDeviceRemoval; destructor Destroy; override; property OnWin: TProc read FOnWin write FOnWin; end; TForm1 = class(TForm) Memo: TMemo; procedure FormCreate(Sender: TObject); procedure FormDestroy(Sender: TObject); private { Private declarations } DeviceNotifier : TDeviceNotifier; public { Public declarations } procedure arrival(Sender: TObject; const DeviceName: String); procedure report (text: string); end; var Form1: TForm1; implementation {$R *.dfm} constructor TDeviceNotifier.Create(GUID_DEVINTERFACE : TGUID); var NotificationFilter: TDevBroadcastDeviceInterface; begin inherited Create; hRecipient := AllocateHWnd(WndProc); ZeroMemory (@NotificationFilter, SizeOf(NotificationFilter)); NotificationFilter.dbcc_size := SizeOf(NotificationFilter); NotificationFilter.dbcc_devicetype := DBT_DEVTYP_DEVICEINTERFACE; NotificationFilter.dbcc_classguid := GUID_DEVINTERFACE; //register the device class to monitor FNotificationHandle := RegisterDeviceNotification(hRecipient, @NotificationFilter, DEVICE_NOTIFY_WINDOW_HANDLE); end; procedure TDeviceNotifier.WndProc(var Msg: TMessage); var Dbi: PDevBroadcastDeviceInterface; begin OnWin (Format ('msg = %d, wparam = %d, lparam = %d', [msg.Msg, msg.WParam, msg.LParam])); with Msg do if (Msg = WM_DEVICECHANGE) and ((WParam = DBT_DEVICEARRIVAL) or (WParam = DBT_DEVICEREMOVECOMPLETE) or (WParam = DBT_DEVICESOMETHING)) then try Dbi := PDevBroadcastDeviceInterface (LParam); if Dbi.dbcc_devicetype = DBT_DEVTYP_DEVICEINTERFACE then begin if WParam = DBT_DEVICEARRIVAL then begin if Assigned(FDeviceArrival) then FDeviceArrival(Self, PChar(@Dbi.dbcc_name)); end else if WParam = DBT_DEVICEREMOVECOMPLETE then begin if Assigned(FDeviceRemoval) then FDeviceRemoval(Self, PChar(@Dbi.dbcc_name)); end; end; except Result := DefWindowProc(hRecipient, Msg, WParam, LParam); end else Result := DefWindowProc(hRecipient, Msg, WParam, LParam); end; destructor TDeviceNotifier.Destroy; begin UnregisterDeviceNotification(FNotificationHandle); DeallocateHWnd(hRecipient); inherited; end; procedure TForm1.arrival(Sender: TObject; const DeviceName: String); begin report (DeviceName); ShowMessage(DeviceName); end; procedure TForm1.FormCreate(Sender: TObject); const GUID_DEVINTERFACE_COMPORT : TGUID = '{86E0D1E0-8089-11D0-9CE4-08003E301F73}'; begin DeviceNotifier:=TDeviceNotifier.Create(GUID_DEVINTERFACE_COMPORT); DeviceNotifier.FDeviceArrival:=arrival; DeviceNotifier.OnWin := report; end; procedure TForm1.FormDestroy(Sender: TObject); begin DeviceNotifier.Free; end; procedure TForm1.report (text: string); begin Memo.Lines.Add (text); end; end. </code></pre>

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