Yacht Devices YDNG-03, Руководство пользователя, Страница: 26 / 48

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07:34:10.921 T NMEA0183 Overflow, TX cycle 5.2 seconds
08:11:25.004 T NMEA0183 Overflow, TX cycle 9.3 seconds, some of the AIS
messages are lost
09:15:12.380 T NMEA0183 Overflow, 310 bytes are lost, check routing settings
All these messages indicate that the Gateway is trying to send more data to NMEA 0183 than allowed
by the port speed. The sixth LED flash will appear red if there is overflow (see V.1).
NMEA 2000 messages have different rates, some data arrives ten times per second and some data arrives
once per minute. The Gateway stores received data in memory, and uses them to generate output NMEA
0183 messages in a cycle. Heading (HDG), depth (DPT), wind (MWV) and COG/SOG (VTG) are sent two
times per cycle, other messages are sent once.
If the port speed is high enough, the Gateway does up to two cycles per second. If the cycle takes more than
2.5 seconds, the overflow LED signal is generated and the overflow record (1st line in the example above)
is adding to the log file.
AIS equipment uses 38400 baud NMEA 0183 connection. If a Gateway’s NMEA 0183 port is set to a lower
speed, or also used to transfer other data, it may not be enough in areas with extensive navigation.
AIS messages received from NMEA 2000 are stored in a dedicated buffer and are sent to NMEA 0183 during
the cycle and extend cycle time. In an area with extensive navigation, you may start to receive overflow
signals and overflow records (2nd line in the example) will mention that some AIS data are lost.
NMEA 0183 data is forwarded from the NMEA 0183 input of the Gateway to the NMEA 0183 output
(off in the factory setting, see VI.5) and has a dedicated buffer, sending to NMEA 0183 during the cycle and
extending the cycle time. Overflow signals and overflow records (3rd line in the example) are generated
if the speed of port is not enough.
The only recommendation to solve overflow errors is to prohibit unnecessary sentences with filters
(see VI.2 – VI.5).