Want to develop a USB HID device?  Need Windows PC application software, but don't want to deal with custom device drivers?  Want to develop a quick and easy host PC application to test your USB HID device? The UsbHidApi dynamic link library (DLL) is for you.  Did you know that you don't need a custom driver to access your USB device.  If it's a Human Interface Class (HID) device, you can take advantage of existing Windows drivers.  Used mainly for keyboards, mice, and joysticks, this class is also well-suited for special-purpose applications including access and control of custom-developed devices.  UsbHidApi encapsulates API calls that give you easy access to your device.  These API calls can be used in any development environment that accepts DLLs (e.g., Visual C++ & Visual Basic).  The API has been tested with the following compilers:

Visual C++ 2008  
Visual C++ 6.0
Visual Basic 6.0

Also compatible with LabView and LabWindows/CVI (see note below). 

Also included is UsbHidApi_NET, a special API version that contains a wrapper for .NET compatibility (see note below).  Compiled using the Visual C++ Toolkit 2003, UsbHidApi_NET is recommended for Visual C++ .NET developers.

Check out these features:

Easy to use API calls - Open( ), Read( ), Write( ), etc.
No custom drivers (uses USB HID drivers already included in Windows)
Develop PC host applications quickly
Write applications for USB HID devices
Two available demonstration applications: Generic and U4x1 (UsbHidApi only)
Free demo source code included:  Visual C++ 6.0 and Visual Basic
VC++ 2008 demo source  (generic demo or U4x1 demo)
VC++ 6.0 demo source (generic demo or U4x1 demo)
VB demo source (generic demo only)
Compatible with LabView and LabWindows/CVI (see note)
Also includes API for Visual C++ .NET developers (see note) 
Use implicit- or explicit-linking (DLL required for both options, included)
Includes dynamic library library (DLL) file

The UsbHidApi is featured in the February 2010 edition of the Nuts & Volts Magazine, the nation's premier how-to magazine. The article describes how to use our API to communicate with a PIC Trainer target board. Click here to view the article reprint (by permission of T&L Publications, Inc). The article was featured as an installment in the "Design Cycle" series by Fred Eady. Click here for subscription details

One of the key elements in developing firmware for your custom USB device is defining the descriptors.  This is important for proper device enumeration by the host.  There are several types of descriptors including configuration, device, and report.  Many times users will define a valid set of descriptors, but fail to properly classify the device. The device is classified by its "usage" such as a keyboard, joystick, or mouse.  These devices are typically allocated for exclusive use by the operating system.  If you are developing a custom device (e.g., temperature controller, digital input/output board, etc.) using the HID class, your report descriptor should indicate a "Vendor Defined" usage as indicated in the sample report descriptor below (courtesy of L. Zadra):

/*------ Report Descriptor Group ---------------------*/
/* This is a basic report descriptor. All data in the */
/* reports are vendor defined and therefore the host  */
/* doesn't care  what we transfer                    */

BYTE code abromReportDescriptor[SIZEOF_REPORT_DESCRIPTOR] =
{
   0x06, 0xA0, 0xFF, // Usage Page (FFA0H = vendor defined)
   0x09, 0x01, // Usage (vendor defined)
   0xA1, 0x01, // Start Collection (Application)

   // INPUT DEFINITION
   0x09, 0x01, // Usage (vendor defined)
   0x15, 0x00, // Logical Minimum (0)
   0x25, 0xff, // Logical Maximum (255)
   0x75, 0x08, // Report Size ( 8 BITS)
   0x95, EP1_MAX_REPORT_SIZE, // Report Count (16 Bytes)
   0x81, 0x00, // Input (Data, Variable, Absolute)

  // OUTPUT DEFINITION
  0x09, 0x02, // Usage (vendor defined)
  0x75, 0x08, // Report Size (8 BITS)
  0x95, EP0_MAX_REPORT_SIZE, // Report Count (16 Bytes)
  0x91, 0x00, // 0utput (Data, Variable, Absolute)
  0xC0 // End Collection
};

U4x1 Software Development

The UsbHidApi comm library is compatible with the UsbMicro U4x1 devices.  Users who want to create their own control software for these devices will find the UsbHidApi library invaluable.  Available in two form-factors: U401 and U421, these devices are functionally identical and provide 16 digital I/O signals configurable in any combination of inputs and outputs.  You can obtain a U4x1 device with our USB Digital I/O Commander product. For complete details on U4x1 hardware and interfacing, refer to the UsbMicro website. 

Control and access of U4x1 device I/O signals involves several steps: 

 1) Open the device

2)  Configure signals (inputs & outputs)

3)  Read/write the device

UsbHidApi has been tested on Windows platforms including 98, 2000, XP, & Vista and has been used with a variety of HID class devices.  For those with compatibility concerns or unusual interfacing requirements, we offer a 30-day unregistered evaluation.  This limited-use version allows you to test the library with your application on a trial basis. 

To request the evaluation, click the link above.  Those interested in programming for applications including .NET and LabView should read the following notices: