User's Manual

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4. Communication interface

4.1 Overview

The RS485 RFID Reader can be controlled using a simple binary protocol available over RS485. This binary

protocol was designed to be as simple as possible to implement on the host side whilst still providing robust

communication.

The default baud rate is 115200 bps, and can be changed from 9600 up to 115200.

Other protocol settings are:

 data bits: 8,

 parity: None,

 Stop bits: 1,

 flow control: None.

4.2 Frame structure

Communication with the module is symmetric. So, frames sent to and received from the module are coded in

the same way. All frames contain fields as described in the table below. The reader should answer only to

commands with an address byte equal to its own device address.

The length of the command is the sum of the Address byte + Command body + 2 bytes CRC.

Frame STX

Command

length

Command length

XOR

Address

byte

Command body CRC16

byte

bytes

byte

bytes

0xF5

Command

body length,

maximum

value 1024,

LSB

XOR with 0xFFFF

of command

length bytes, LSB

Address

byte

Command

parameters

Address +

Command

body CRC,

LSB