How to determine when a USB device is connected / disconnected?

Question

I don’t feel comfortable using a USB device with Delphi and know almost nothing about the details of writing a device driver (although I come up with something when learning about assembly using GoASM).

The device can be either a USB modem or a USB printer.

What I need is a direction to go, and an example of code devoted to the topic.

Answer 1

This was taken to determine if a 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. 

Answer 2

For this you can use some shell script . when the device is connected, the lsusb command shows this and removes it from the list after disconnecting the device. So in your shell script you need to find the difference between the old list and the current list. Finally, you need to run this script as a cron job that is checked at frequent intervals.

Regards, Barun Paricha