Safety Instructions

SYMEO LPR
®
LPR-1D
Product Documentation
Protocol Description Binary XP (1D messages)
Copyright © Symeo GmbH 2010
Page 72 of 87
7.3 TCP/IP option: Fixed Frame Protocol
If the LPR
®
station has a TCP/IP interface two options are available for the protocol. Either
you use the protocol as it is sent from the serial interface (with different data type lengths,
byte stuffing) or you use a fixed frame protocol.
In the first case the data symbols 0x7e und 0x7f (which are reserved for the START and
END field) are replaced (see chapter 7.1.3). Byte stuffing causes a different protocol length.
For the fixed frame protocol each LPR
®
data packet is filled up with zero bytes to a fixed
length of bytes (i.e. 87 bytes) before the data packet is sent. Byte stuffing does not occur.
The START and the END byte are still used but not clear anymore due to not applying byte
stuffing. The fixed length of the data packets can be set on the web-interface of the LPR
®
unit.
For the fixed frame protocol the data packets which are sent to a LPR
®
unit has to be filled up
to a fixed length (i.e. 15 bytes). The START- and the END byte have to be occurred as well
and byte stuffing does not occur anymore. It is recommended to fill up the data packet with
zero bytes to facilitate a troubleshooting.
If TCP/IP is used the transmitted data have already a checksum. Therefore the checksum in
the protocol is not as important as for the serial interface. Two options for the fixed frame are
allowed by the protocol inverter for receiving data in a fixed frame. Either 0x0000 is sent as
the check sum to the LPR
®
unit. Then the protocol inverter is calculating the check sum itself.
Or another value (differing to 0x0000) is sent as the check sum. Then this check sum is
assumed to be the correct check sum. Otherwise the data packet is rejected.
7.3.1 Detailed description TCP Fixed-Frame Protocol
If a TCP fixed-frame protocol is used, a working TCP connection between the PC and the
LPR
®
unit has to be guaranteed. Depending on the configuration of the LPR
®
protocol
inverter either the connection to a port on the LPR
®
has to be initialized from the PC or the
LPR
®
unit is establishing a connection to a PC.
If the connection is established, the PC has to read the data from the LPR
®
in fixed data
length (i.e. 87 bytes). The first byte is always the START-byte and the second byte is always
the TYPE-byte. The relevance of the following data is depending on the data type. Because
no byte stuffing occurs the content for a special data type is always constant. For example
the measured velocity of the distance data (type 0x00) is always written in the 12.-15 data
byte.
Sending data from the PC to LPR
®
station, a fixed data length has to be chosen (i.e. 15
byte). The first byte (START byte: 0x7e) follow the TYPE-byte. The following data depends
on the chosen type, following by the CRC (correct CRC or 0x0000), following by the STOP
byte (0x7f). The data packed has to be filled up with zeros.
7.3.2 Detailed description UDP Fixed-Frame Protocol
If a UDP fixed frame protocol is used, the IP and the UDP port of the PC has to be
configured in the LPR
®
protocol inverter. The converter sends each data packet as a UDP
packet of a fixed length (87 byte) to the PC. Compared to the TCP fixed frame option the
UDP fixed frame does not verify if the data packed arrived.
The content is the same as for the TCP fixed frame protocol.