Omron V740-BA50C22A-US Operation Manual page 33

SELECT id FROM tag_id WHERE
protocol_id='EPC1' AND antenna_id=1
AND (tag_id>=min_tag_id AND
tag_id<=max_tag_id);
The reader returns the tag ID values for all the
present tags between min_tag_id and
max_tag_id, which are hexadecimal values.
•
To query tags by specific or all antennas:
SELECT id FROM tag_id WHERE
antenna_id=1 AND protocol_id='EPC1';
SELECT id FROM tag_id WHERE
protocol_id='EPC1';
At the first, the reader searches tags only by
antenna 1. Second the reader searches tags by
all antennas available. Omitting the antenna
indication in the 'where_specification' means to
search all antennas available.
Note: When specifying multiple antennas even if
an antenna that does not exist is specified, the
reader obtains the tag ID only using antenna 1
and doesn't return any an error message.
SELECT id FROM tag_id WHERE
(antenna_id=1 OR antenna_id=5) AND
protocol_id='EPC1';
•
The client software can specify multiple entries in
the select_list field of the SELECT command:
SELECT id, antenna_id FROM tag_id
WHERE antenna_id=1 AND
protocol_id='EPC1';
SELECT protocol_id, timestamp, id,
antenna_id FROM tag_id WHERE
antenna_id=1 AND protocol_id='EPC1';
The first example returns the tag IDs and
antenna_ids, and the second returns protocol_ids
and the time that the tag was read (seconds from
the unix epoch, Jan 1, 1970) with the tag IDs and
antennas_ids.
Note: To read timestamp, the NTP sever must be
set up in advance.
The reader returns protocol_id as an integer value.
The value '1' represents 'EPC1'. For example, the
query with protocol_id and the response is as
follows:
[Query] SELECT protocol_id, id FROM
tag_id WHERE antenna_id=1 AND
protocol_id='EPC1';
[Res] 1|0xCE791111111111111111<LF><LF>
•
To query during a specific time:
V740 RFID READER/WRITER, ANTENNA
OPERATION MANUAL
SELECT id FROM tag_id WHERE
antenna_id=1 AND protocol_id='EPC1'
SET time_out=500;
The command imposes a time out constraint of
500ms; i.e., the reader stops reading and returns
all collected data after 500ms. The order in which
specifying arguments are used is irrelevant. The
default timeout is 250ms if none is specified.
It is important to always use a timeout in
specifying a query to achieve optimal performance
for a given application. Detailed information will be
discussed in the next section
Timeout
The client software can impose a time limit on a read
operation, requesting the reader to search only for a
limited time (specified in milliseconds). The reader
may fail to detect some tags if insufficient time is
allocated to the search operation. The time_out is the
parameter used for specifying the time allocated for
the read operation.
Conveyor
short
In general, a large time_out should be used for dock
stations (>2000ms), and short time_outs should be
used for conveyor belts (<100ms).
SELECT id FROM tag_id WHERE antenna_id=1
AND protocol_id='EPC1' SET
time_out=1000;
(See 3.2 Communications Time)
The constraints on the scheduler in the reader for the
time_out are shown below. The reader searches
sequentially for each antenna in the time. When the
last antenna completes searching, the reader returns
to the first antenna again. Following chart shows an
example of time schedule given by the model
command as below.
SELECT id FROM tag_id WHERE
(protocol_id='protocol1') and
(antenna_id=ant1 or antenna_id=ant2 or
antenna_id=ant3 or antenna_id=ant3);
ant1 ant2
33 of 56
Application
time out
time_out
ant3 ant4 ant1
©OMRON CORPORATION 2005
Dock
Station
long
...
ant2
2005-09, REV0.1