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Each new version of firmware is 'tested-to-destruction' before it is released
on this website, so you can be sure that upgrading your Actisense product
to the latest version will be a win-win situation. Please check the Firmware
updates page for the latest updates.
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NDC-1/2: Why is some NMEA data missing from the
combined NMEA output?
There could be a number of reasons for this:
A) If there is a heavy load on one or more channels, then the
port priority algorithm has come into action to reduce the load to a level
that can be handled by the NMEA output. This is determined by the NMEA
0183 standard using the very slow Baud rate of 4800, and is normally fixed
at this rate.
This situation will manifest itself as random sentences being dropped from
the lowest priority input channel (by default this is set to channel 4)
- this is not a failing of the NDC unit and is necessary because of the
limited bandwidth of the NMEA 0183 standard.
It is important to stress that all NMEA input data will appear in the RS232
/ PC output data stream - as that has a high enough bandwidth / Baud rate
to manage under all conditions (including 100% loading on all 4 input channels).
The answer is to connect the NDC unit to a PC, and using
the Control Centre software, monitor the input channel loading's on the
NDC unit (refer to the User Manual for details on how to achieve this).
If the total of all input channel loading percentages exceeds 95% then
you have your answer - the load is too high for a place to be found for
all the NMEA data in the NMEA combined output.
However, if you monitor the RS232 combined channel you should see the sentences
that are missing. The 'Inclusion Lists' can be used to reduce the loading
of a channel by removing sentences that are not required.
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B) If the same sentence or sentences are always missing,
then it will most probably be due to this sentence or sentences being omitted
from the 'Inclusion List' of that input channel (and so has been filtered
out by the NDC).
The answer is to connect the NDC unit to a PC, and using
the Control Centre software, read the 'Inclusion Lists' from the NDC unit.
If the missing sentences are indeed 'unchecked' (not included), then check
the boxes and click the 'OK' button to program the new 'Inclusion List'.
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1. Download the latest driver file for your OS from the Software
updates page.
2. Download (or simply view on this website) the Updating
(USB) driver document, and follow the steps it details to correct this
driver issue.
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NDC-3: Why is some NMEA data missing from the combined
NMEA output?
This is normally due to heavy loading on one or more input channels, which
has activated the port priority algorithm to help reduce the load to a
level that can be handled by the NMEA output. This is determined by the
NMEA 0183 standard using the very slow Baud rate of 4800, and is normally
fixed at this rate.
This situation will manifest itself as random sentences being dropped from
the lowest priority input channel (by default this is set to channel 4)
- this is not a failing of the NDC unit and is necessary because of the
limited bandwidth of the NMEA 0183 standard.
It is important to stress that all NMEA input data will appear in the RS232
/ PC output data stream - as that has a high enough bandwidth / Baud rate
to manage under all conditions (including the case of 100% loading on all
4 input channels).
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The answer is to view and compare the data on the RS232
and NMEA out channels - you will see the missing data on the RS232 channel
but not on the NMEA combined out channel.
The NDC-3 has intelligent software algorithms to decide what data to drop,
and what data to keep (based on its priority and frequency). This should
mean that the data that must be dropped (due to more data coming in than
is possible to send back out), is of the lowest priority possible.
To have
further control over this operation, the NDC-2 is available with full NMEA
0183 sentence filtering - these 'Inclusion Lists' can be used to reduce
the loading of a channel by removing sentences that are not required.
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