Question

I’ve found several snippets and .pas files that can detect when USB flash drives are inserted and removed. Some give all kind of good information, however what I need is the devices’ unique serial number, not the volumes’ serial number.

My current .pas file (which I don’t remember where I found) also seems to detect SD cards (which I like). If you want a look, you can find it here (it only returns the drive number and inserted/removed):

unit UsbDetector;

interface

uses Classes;

type
  TUsbDriveChanged = procedure (Sender: TObject; Drive: string; Attached: boolean) of object;

procedure StartUsbDetector(NotifyProc: TUsbDriveChanged);
procedure StopUsbDetector;

implementation

uses Windows, Messages, Forms, SysUtils;

type
  TUSBDetector = class(TObject)
  private
    fUsbDriveChanged: TUsbDriveChanged;
  protected
    procedure DeviceChanged(Msg: UINT; wParam, lParam: Longint);
    procedure DoUsbDriveChanged(Drive: string; Attached: Boolean); dynamic;
  public
    constructor Create(NotifyProc: TUsbDriveChanged);
    destructor Destroy; override;
    property OnUsbDriveChanged: TUsbDriveChanged read fUsbDriveChanged;
  end;

var mUSBDetector: TUSBDetector;

procedure StartUsbDetector(NotifyProc: TUsbDriveChanged);
begin
  if not Assigned(mUsbDetector) then
    mUsbDetector := TUsbDetector.Create(NotifyProc);
end;

procedure StopUsbDetector;
begin
  FreeAndNil(mUsbDetector);
end;

{----------------------------------------------------------------------------}
// Device constants
const
  DBT_DEVICEARRIVAL          =  $00008000;
  DBT_DEVICEREMOVECOMPLETE   =  $00008004;
  DBT_DEVTYP_VOLUME          =  $00000002;

// Device structs
type
  _DEV_BROADCAST_HDR         =  packed record
     dbch_size:              DWORD;
     dbch_devicetype:        DWORD;
     dbch_reserved:          DWORD;
  end;
  DEV_BROADCAST_HDR          =  _DEV_BROADCAST_HDR;
  TDevBroadcastHeader        =  DEV_BROADCAST_HDR;
  PDevBroadcastHeader        =  ^TDevBroadcastHeader;

type
  _DEV_BROADCAST_VOLUME      =  packed record
     dbch_size:              DWORD;
     dbch_devicetype:        DWORD;
     dbch_reserved:          DWORD;
     dbcv_unitmask:          DWORD;
     dbcv_flags:             WORD;
  end;
  DEV_BROADCAST_VOLUME       =  _DEV_BROADCAST_VOLUME;
  TDevBroadcastVolume        =  DEV_BROADCAST_VOLUME;
  PDevBroadcastVolume        =  ^TDevBroadcastVolume;

var
  fPrevWndProc: TFNWndProc = nil;

function UsbWndProc(hWnd: HWND; Msg: UINT; wParam, lParam: Longint): Longint; stdcall;
begin
  Result := CallWindowProc(fPrevWndProc, hWnd, Msg, wParam, lParam);
  if (Msg = WM_DEVICECHANGE) and (mUsbDetector <> nil) then
    mUsbDetector.DeviceChanged(Msg, wParam, lParam);
end;

constructor TUSBDetector.Create(NotifyProc: TUsbDriveChanged);
begin
  inherited Create;
  fUsbDriveChanged := NotifyProc;
  if not Assigned(fPrevWndProc) then 
  begin
    fPrevWndProc := TFNWndProc(GetWindowLong(Application.Handle, GWL_WNDPROC));
    SetWindowLong(Application.Handle, GWL_WNDPROC, LongInt(@UsbWndProc));
  end;
end;

destructor TUSBDetector.Destroy;
begin
  //SetWindowLong(Application.Handle, GWL_WNDPROC, LongInt(@fPrevWndProc));
  inherited Destroy;
end;

procedure TUSBDetector.DeviceChanged(Msg: UINT; wParam, lParam: LongInt);
var
  lpdbhHeader: PDevBroadcastHeader;
  lpdbvData: PDevBroadcastVolume;
  dwIndex: Integer;
  lpszDrive: string;
begin
  // Get the device notification header
  lpdbhHeader := PDevBroadcastHeader(lParam);
  // Handle the message
  lpszDrive := '';
  case WParam of
    DBT_DEVICEARRIVAL:    {a USB drive was connected}
    begin
      if lpdbhHeader^.dbch_devicetype = DBT_DEVTYP_VOLUME then
      begin
        lpdbvData := PDevBroadcastVolume(lParam);
        for dwIndex := 0 to 25 do
        begin
          if (lpdbvData^.dbcv_unitmask shr dwIndex) = 1 then
          begin
            lpszDrive := lpszDrive + Chr(65 + dwIndex) + ':\';
            break;
          end;
        end;
        DoUsbDriveChanged(lpszDrive, True);
      end;
    end;
    DBT_DEVICEREMOVECOMPLETE:    {a USB drive was removed}
    begin
      if lpdbhHeader^.dbch_devicetype = DBT_DEVTYP_VOLUME then
      begin
        lpdbvData := PDevBroadcastVolume(lParam);
        for dwIndex := 0 to 25 do
        begin
          if (lpdbvData^.dbcv_unitmask shr dwIndex) = 1 then
          begin
            lpszDrive := lpszDrive + Chr(65 + dwIndex) + ':\';
            break;
          end;
        end;
        DoUsbDriveChanged(lpszDrive, False);
      end;
    end;
  end;
end;

procedure TUSBDetector.DoUsbDriveChanged(Drive: string; Attached: Boolean);
begin
  if Assigned(fUsbDriveChanged) then
    fUsbDriveChanged(Self, Drive, Attached);
end;

end.

P.S. The code highlight is fail.

All in all;
When a removable is inserted/removed, get drive letter and its unique serial number. Maybe combine the already given code with a WMI call “where Index=found_index”.

****EDIT!****
I removed the “where” clause in the code given by RRUZ. I finally found out how to handle the arrays, so I use that to find Capabilities[i]=7 to get all removable media. Now I just need to connect this code with the above code. I am thinking using Index, but I don’t know how to use GetDrive MapInfo. If you could provide me with an example on getting the drive letter, my question is solved.

Answer 1

You can use the WMI library by Magenta Systems which takes most of the pain of using WMI queries. The free download includes source and an example project that allows you to play with the API and queries to your hearts content. You will want to keep a link to the official Microsoft API documentation which will help you with what query to execute to get what information…your interested in querying the classes using SQL like syntax queries.

For example, executing the query

SELECT * FROM Win32_DiskDrive Where InterfaceType = 'USB'

returns a wealth of information about all of the USB devices currently connected to the machine. You can then use the PNPDeviceID as a unique identifier.

EDIT checking the only USB device I had handy returned a hardware serial number of “u” but a very long and valid looking PNPDeviceID which appeared to include a serial number, which is why I suggested that field.

EDIT You can get the drive letter by performing a query against Win32_LogicalDisk you can also query Win32_DiskDriveToDiskPartition which contains a mapping between Win32_DiskDrive and Win32_DiskPartition. Finally Win32_LogicalDiskToPartition then maps a logical disk to a partition which in turn gives you the ability to link a physical USB drive to a specific drive letter.