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//detect if a USB device is connected or disconnected?
//autor: miguel lucero
//homepage: www.lsis.com.ar
// component to detect when usb devices are connected or disconnected
// using registerdevicenotification

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;

procedure Register;

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;

procedure Register;   { add this in the implementation section }
begin
  RegisterComponents('Samples', [TComponentUSB]);
end;

end.