MagTek MagneSafe V5 - Manual (Page 29)

Section 2. Communications
21
Low Level Communications
It is strongly recommended that application software developers become familiar with the HID
USB specification before attempting to communicate directly with this reader. This document
assumes that the reader is familiar with these specifications. These specifications can be
downloaded free from
www.usb.org .
COMMANDS
Most host applications do not need to send commands to the reader. Most host applications only
need to obtain card data from the reader as described previously in this section. This section of
the manual can be ignored by anyone who does not need to send commands to the reader.
Commands sent to the wireless reader model will only succeed if the reader is both on and within
range of the dongle.
With serial readers, each command and response is composed of a series of readable ASCII
characters followed by the ASCII character CR (0x0D). The ASCII characters preceding the CR
are the message. There should always be an even number of these characters and they should
contain only the characters “0123456789ABCDEF”. The receiver will combine two successive
ASCII characters from the message to form one byte (see the descriptions of the commands)
which may have any value from 0x00 to 0xFF.
For USB HID readers, command requests and responses are sent to and received from the reader
using feature reports. Command requests are sent to the reader using the HID class specific
request Set Report. The response to a command is retrieved from the reader using the HID class
specific request Get Report. These requests are sent over the default control pipe. When a
command request is sent, the reader will NAK the Status stage of the Set Report request until
the command is completed. This insures that, as soon as the Set Report request is completed,
the Get Report request can be sent to get the command response. The usage ID for the
command message was shown previously in the Usage Table.
The following table shows how the feature report is structured for command requests:
Offset Field Name
0 Command Number
1 Data Length
2 – 49 Data
The following table shows how the feature report is structured for command responses.
Offset Field Name
0 Result Code
1 Data Length
2 – 49 Data