Question

I don’t feel comfortable harnessing USB device with Delphi and have a next to nothing knowledge of the details of writing device driver (though I’ve come accross some when learning assembly with GoASM).

The device could be either an usb modem or an usb printer.

What I need is a direction to go and sample code adressing the topic.

Answer 1

This was taken from detect if usb device is connected

 unit U_Usb;

 interface

uses
Windows, Messages, SysUtils, Classes, Forms;

type

PDevBroadcastHdr = ^DEV_BROADCAST_HDR;
DEV_BROADCAST_HDR = packed record
dbch_size: DWORD;
dbch_devicetype: DWORD;
dbch_reserved: DWORD;
end;

PDevBroadcastDeviceInterface = ^DEV_BROADCAST_DEVICEINTERFACE;
 DEV_BROADCAST_DEVICEINTERFACE = record
 dbcc_size: DWORD;
 dbcc_devicetype: DWORD;
 dbcc_reserved: DWORD;
  dbcc_classguid: TGUID;
  dbcc_name: short;
 end;

const
  GUID_DEVINTERFACE_USB_DEVICE: TGUID = '{A5DCBF10-6530-11D2-901F-00C04FB951ED}';
  DBT_DEVICEARRIVAL = $8000; // system detected a new device
  DBT_DEVICEREMOVECOMPLETE = $8004; // device is gone
  DBT_DEVTYP_DEVICEINTERFACE = $00000005; // device interface class

type

 TComponentUSB = class(TComponent)
   private
   FWindowHandle: HWND;
   FOnUSBArrival: TNotifyEvent;
   FOnUSBRemove: TNotifyEvent;
   procedure WndProc(var Msg: TMessage);
   function USBRegister: Boolean;
   protected
   procedure WMDeviceChange(var Msg: TMessage); dynamic;
  public
  constructor Create(AOwner: TComponent); override;
  destructor Destroy; override;
  published
    property OnUSBArrival: TNotifyEvent read FOnUSBArrival write FOnUSBArrival;
    property OnUSBRemove: TNotifyEvent read FOnUSBRemove write FOnUSBRemove;
  end;

  implementation

constructor TComponentUSB.Create(AOwner: TComponent);
   begin
     inherited Create(AOwner);
     FWindowHandle := AllocateHWnd(WndProc);
     USBRegister;
   end;

   destructor TComponentUSB.Destroy;
    begin
   DeallocateHWnd(FWindowHandle);
    inherited Destroy;
   end;

 procedure TComponentUSB.WndProc(var Msg: TMessage);
     begin
     if (Msg.Msg = WM_DEVICECHANGE) then
      begin
      try
      WMDeviceChange(Msg);
    except
  Application.HandleException(Self);
   end;
   end
  else
     Msg.Result := DefWindowProc(FWindowHandle, Msg.Msg, Msg.wParam, Msg.lParam);
   end;

  procedure TComponentUSB.WMDeviceChange(var Msg: TMessage);
   var
   devType: Integer;
     Datos: PDevBroadcastHdr;
   begin
    if (Msg.wParam = DBT_DEVICEARRIVAL) or (Msg.wParam = DBT_DEVICEREMOVECOMPLETE) then
    begin
  Datos := PDevBroadcastHdr(Msg.lParam);
    devType := Datos^.dbch_devicetype;
     if devType = DBT_DEVTYP_DEVICEINTERFACE then
    begin // USB Device
     if Msg.wParam = DBT_DEVICEARRIVAL then
     begin
      if Assigned(FOnUSBArrival) then
       FOnUSBArrival(Self);
       end
        else
      begin
     if Assigned(FOnUSBRemove) then
      FOnUSBRemove(Self);
   end;
  end;
   end;
  end;

  function TComponentUSB.USBRegister: Boolean;
    var
      dbi: DEV_BROADCAST_DEVICEINTERFACE;
       Size: Integer;
     r: Pointer;
      begin
     Result := False;
     Size := SizeOf(DEV_BROADCAST_DEVICEINTERFACE);
      ZeroMemory(@dbi, Size);
      dbi.dbcc_size := Size;
      dbi.dbcc_devicetype := DBT_DEVTYP_DEVICEINTERFACE;
     dbi.dbcc_reserved := 0;
     dbi.dbcc_classguid := GUID_DEVINTERFACE_USB_DEVICE;
     dbi.dbcc_name := 0;

     r := RegisterDeviceNotification(FWindowHandle, @dbi,
      DEVICE_NOTIFY_WINDOW_HANDLE
     );
      if Assigned(r) then Result := True;
    end;

    end.