III. Low level communication protocol
A. Serial port settings
The low level communication protocol can be used with and hardware flow control capable
RS232 device (PLC, SBC, industrial computer, etc.)
Communication parameters are:
•
baud rate – 115200 (could be delivered with other baud rates upon request)
•
data bits – 8
•
stop bits – 1
•
parity – None
•
hardware flow control (RTS/CTS)
B. Low level protocol messages
Every message consists of a message header, message data and CRC. The CRC is
calculated by an XOR operation of the message header and message data bytes.
Every time a command or a response is sent, the other device should answer with ACK or
NACK, accordingly.
ACK message is: 0xFC 0xFC 0xFC 0xFC 0x00
NACK message is: 0xFD 0xFD 0xFD 0xFD 0x00
As a convention for the protocol description tables, B0, B1, … Bn represents “byte
number” and b0, b1, … bn represents “bit number”. Also, we will refer to this interface as
“device” or as “bridge”
