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NEO 2 Interface Developer’s Guide
Copyright © 2019, International Technologies & Systems Corporation. All rights reserved.
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2.7.2.
Basic Communication
The ViVOpay reader and the POS terminal communicate by exchanging command-response
frames. The terminal always initiates communication by sending a command frame and
ViVOpay responds by sending a response frame. The frames that are exchanged depend on
the command and the protocol used. There are two command/response protocols. Protocol 1,
now deprecated, uses separate data frames and ACK/NACK responses. Protocol 2 is simplified
by including data within the command/response frames.
2.7.3.
Timeouts
The ViVOpay reader does not timeout while trying to receive a command. There is no
maximum inter-character delay. As a result, command frames with length errors may appear
to “hang”. A subsequent command that does not contain a length error can be received
successfully.
After the ViVOpay reader has received a command, the time required to respond to the
terminal varies from command to command, depending on what processing is required.
During a transaction, the
Activate Transaction
command may specify a timeout value. The
reader will continue to poll until it starts to process a transaction, or the specified timeout
period has elapsed. The transaction may not complete within the timeout period.
2.8.
USB HID Interface
All ViVOpay commands sent over the USB HID interface are encapsulated in the following
protocol.
Note:
The maximum length for any command or response is 1500 bytes, which is the size
of the command FIFO buffer.
2.8.1.
HID Report Format
All HID reports sent to or received from the ViVOpay are in frames that are 64 bytes long. The
first byte of the frame is a single byte report ID number. The remaining 63 bytes carry the
report payload. Any reports with less than 63 bytes of command or response data are padded
with NULL bytes (00h) to make them 63 bytes long.
ViVOpay commands and responses are sent over the USB bus in 63-byte frames. Byte
ordering in the USB frame is the same as if the command were sent over the serial port. In
other words, the “ViVOtech2” command tag always starts in the second byte of the first report
containing the command, just after the Report ID.