Silicon Laboratories Stepper Machine Specifications download pdf (Page 41)

 HID Class originally developed to for human interface objects such as

mice and keyboards

 Interrupt transfers used for data transport

 Any device can use the HID drivers. It does not need to be a human

interface device device.

 Volt meters

 Bar code readers

 Thermometers

 What do I need?

 Firmware side

 The firmware needs to set the standard descriptors and set the appropriate

report descriptors

 Must support the standard requests as well as the HID specific requests

 Host side

 Need the Windows DDK to get the library functions to read and write the

data to the HID device

Human Interface Device (HID)

There are some things to be considered based on the class definition chosen for the

application. The next few slides discuss some of the standard classes and what is

required to implement them. For example, the HID class is useful for applications

where the data transfer rate is less than 64Kbps. This is due to the fact that it uses

interrupt transfers and they have a maximum packet size of 64 bytes and a minimum

interval of 1ms. If the application fits within those requirements then the

descriptors on the device side will need to reflect those called out in the HID

specification. The firmware will have to support the standard requests associated

with the USB 2.0 specification as well as those for the HID specification such as

Get_Report. On the host side the calls to the driver are available in the Windows

Driver Development Kit (DDK) or a manufacturer like Silicon Labs can provide

their own API.

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Silicon Laboratories Stepper Machine Specifications Page 41