Online Development Notebook > Index > Programming Overview > DLL Commands > DeviceValid

DeviceValid - Return a device-present indication


This is a USBm.dll function that returns indication of validity from a USB device.

Command Syntax:

true⁄false USBm_DeviceValid( device )

The USBm_DeviceValid function syntax has these parts:

Part Description
device Valid device from 0 to the maximum number of devices found (minus 1) . Any other number results in a FALSE return.


Note: USBm_DeviceValid always returns TRUE if the device is valid, otherwise FALSE.

VB Declaration (USBmAPI.bas)

Public Declare Function USBm_DeviceValid _
    Lib "USBm.dll" _
        (ByVal device As Byte) _
    As Integer

VB Example

Dim result As Integer

    result = USBm_DeviceValid 3

This code fragment shows that result is loaded with TRUE if device three exists, or with FALSE if the device does not exist.

C Prototype

int USBm_DeviceValid( unsigned char device );

C Example



Returns true if the device number refers to a connected and active device. False otherwise.

Hardware:  U401 USB Interface    U421 USB Interface   U451 USB Interface

Programming:  USBm DLL Programming    Download Files

Application Notes:  U4x1 Application Notes    Misc Applications and Information    FAQ

While every effort has been made to make sure that the information posted on this site is correct, the author can not be held liable for any damages whatsoever for losses as a result of the application of this information. Use this information at your own risk.

USBmicro can design your custom and semi-custom USB product. Email about USB design can be directed to " Robert " at

Copyright © USBmicro, L.L.C., 2002-2010

Previous  |  Next ]     [ Up  |  First  |  Last ]     (Article 43 of 126)

This page is created with TreePad