[gpsd-users] QT program with Libgpsmm delivers wrong NMEA data

[Ulrich Betzenbichler]

Hello,

 

I try to use gpsd 3.9 on a SOC platform with Linux 3.10.16 and QT 5.0

We have the GPS device on board. The program supplies the gps-data (NMEA) as a stream on the file system (/data/gps/agiin).

The gpsd daemon is started with following parameter

 

Gpsd –b –n –P /var/run/gpsd.pid /data/gps/agiin 

 

Gpsd itself works. I have tested  it with gpsmon.

 

I have created a program that uses libgpsmm to connect to gpsd.

I try to read the NMEA data.

 

I use the attached procedures (see GNSSViewr.cpp)

(This is not a runnable program. It’s only the parts to read the data in a loop.)

 

.

The problem is, that it reads always the same data and much more data that are exported every seconds.

This file show the read data.

 

Each time when a line shows a ‘time  : number’ (e.g. 01:06:34 : 9) a new loop is started. The number at the end shows the number of readed lines.

 

If you look e.g. at the ‘GPGGA’ sentences, you can see that the same data are shown repeated.

The actual data are missing.

 

I think there is some kind of buffer that is never been deleted and if the buffer is full, no new data are added.

Is there a possibility to delete this buffer after reading?

 

Best regards

 

Uli Betzenbichler

 

 

 

 

 

 

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gnssviewer.cpp
Description: gnssviewer.cpp

GNSSViewer.log
Description: GNSSViewer.log