USB : USB Classes    USB Classes for Microcontrollers  

So, what's the catch?  Is there any bad news about HID class?

HID class devices mostly use the Interrupt transfer type, which for a full speed device, is limited to a maximum of 1 64-byte packet every 1 msec frame, or 64,000 bytes per second per USB Interface.  For a few folks, that may not be fast enough.  However, 64,000 bytes/sec is WAY faster than your old RS-232 serial port ever was, yet HID devices are also way smarter, too!  So, full speed HID class devices are great for any application that used to use a serial port.

The other thing that prevents chip manufacturers from showing HID class applications for their chips is that, because a HID device must exhaustively describe itself to the PC, it is harder to write a HID device from scratch, without a tool like HIDmaker FS to help.  That's why you never see any HID examples of any practical complexity in any of that "free software" you get from your chip or compiler manufacturer.

(Of course, with a powerful tool like HIDmaker FS, it is ridiculously easy to make a smart, convenient, and powerful HID device, in just a few minutes, as our customers know.)

The rest of the supposed "limitations" of HID class devices that you might hear about are all misconceptions.  The real problem is that most developers have never even seen a fully functional HID device. That's why we've made these tutorials.



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