Section 4. USB Communications
the device so that the application developer is not burdened with these low level details. Details
on how to communicate with the device to change programmable configuration properties
follows in the next few sections. These details are included as a reference only. Most users will
not need to know these details because the device will be configured at the factory or by a
program supplied by MagTek. Most users may want to skip over the next few sections on low
level communications and continue with the details of the configuration properties.
LOW LEVEL COMMUNICATIONS
It is strongly recommended that application software developers become familiar with the HID
specification the USB specification before attempting to communicate directly with this device.
This document assumes that the reader is familiar with these specifications. These specifications
can be downloaded free from www.usb.org
.
HID USAGES
HID devices send data in reports. Elements of data in a report are identified by unique identifiers
called usages. The structure of the device’s reports and the device’s capabilities are reported to
the host in a report descriptor. The host usually gets the report descriptor only once, right after
the device is plugged in. The report descriptor usages identify the devices capabilities and report
structures. For example, a device could be identified as a keyboard by analyzing the device’s
report descriptor. Usages are four byte integers. The most significant two bytes are called the
usage page and the least significant two bytes are called usage IDs. Usages that are related can
share a common usage page. Usages can be standardized or they can be vendor defined.
Standardized usages such as usages for mice and keyboards can be found in the HID Usage
Tables document and can be downloaded free at www.usb.org
. Vendor defined usages must
have a usage page in the range 0xff00 – 0xffff. All usages for this device use the standard HID
keyboard usages or vendor defined magnetic stripe reader usage page 0xff00. The vendor
defined usage IDs for this device are defined in the following table. The usage types are also
listed. These usage types are defined in the HID Usage Tables document.
Magnetic Stripe Reader usage page 0xff00:
Usage ID
(Hex)
Usage Name Usage
Type
Report
Type
20 Command message Data Feature
13
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