USB to SPI interface HID techniques

If a circuit has to be interfaced to a computer, the interface that is most likely to be used is a USB interface. If it is wireless, either a wireless USB or a Bluetooth LE type interface. Among the two of these, the USB interface is simpler. We have decided to use it in some of our products for analog and wirelss applications.

It is interesting that the simplest USB interface that can be used is a fixed function Human Interface Device interface or HID. This does not require extensive effort to program drivers or other complicated software. The snag is however, that the data transfer rate is somewhat limited to about 64 KBS.

Getting information about HID devices and tutorials for the newbie is really quite difficult, and it seems that USB interfacing is a bit of a black art. We are currently building USB interfaces using HID technology for a USB to SPI bridge application.

The SPI format is used in a programmable RF amplifier for control. The other side is of course the computer. Measurement data of the gain of the amplifier is also interfaced to the USB port. Our intent is to share our experience and design information to all. Keep tuned if interested.

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