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[gpsd-dev] data inconsistency between socket interface vs shared memory


From: Chang, Chia Huang
Subject: [gpsd-dev] data inconsistency between socket interface vs shared memory interface
Date: Thu, 27 Aug 2015 17:30:06 +0000

Hi,

 

In testing both the shared memory and socket interfaces using the nmea0183 protocol we’ve observed some differences:

 

e.g. 

1. The set member state that contains various flags to indicate what new data are available is different between socket and shared memory interface.  Certain flags in the socket interface do not seem to be turned on , such as ONLINE_SET.  Is the difference designed to be that way or something is not configured correctly?

2.  The satellites_used reported by socket interface vs shared memory interface may be different.  E.g.  socket reports initially 0 and then 9 after a while but shared memory starts with 12 and alternates between 10-12.  There seems to be various places that’s assigning the value to satellites_used by the code, at times assigning directly from fields of nmea messages and at times comparing prn of the satellites to increment the count.  It seems that socket and shared memory interfaces fetch the count from different sources?  Is this correct or I am not understanding how the satellites_used count is being set?

 

Thanks,

Bill Chang

Senior Embedded Software Engineer

TCI

SPX Corporation


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www.spx.com

 


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