Problem with searial port reading

2012 6 16
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更新时间：2021 8 20
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Hello i am tryng to read from a serial port device.The divice is a parallax gps receiver. The output of the device is NMEA protocol.The output looks like this:
$GPGSV,3,3,11,18,07,324,25,07,03,091,,11,01,058,*45 $GPRMC,110725.000,A,4313.3418,N,02756.2409,E,0.00,248.59,070612,,,A*6C $GPGGA,110726.000,4313.3418,N,02756.2409,E,1,06,1.4,164.7,M,37.0,M,,0000*5E $GPGSA,A,3,17,26,18,05,15,09,,,,,,,2.1,1.4,1.6*30 $GPRMC,110726.000,A,4313.3418,N,02756.2409,E,0.00,248.59,070612,,,A*6F $GPGGA,110727.000,4313.3418,N,02756.2409,E,1,06,1.4,164.7,M,37.0,M,,0000*5F $GPGSA,A,3,17,26,18,05,15,09,,,,,,,2.1,1.4,1.6*30 $GPRMC,110727.000,A,4313.3418,N,02756.2409,E,0.00,248.59,070612,,,A*6E $GPGGA,110728.000,4313.3418,N,02756.2409,E,1,06,1.4,164.7,M,37.0,M,,0000*50 $GPGSA,A,3,17,26,18,05,15,09,,,,,,,2.1,1.4,1.6*30 $GPRMC,110728.000,A,4313.3418,N,02756.2409,E,0.00,248.59,070612,,,A*61 $GPGGA,110729.000,4313.3418,N,02756.2409,E,1,06,1.4,164.7,M,37.0,M,,0000*51 $GPGSA,A,3,17,26,18,05,15,09,,,,,,,2.1,1.4,1.6*30 $GPRMC,110729.000,A,4313.3418,N,02756.2409,E,0.00,248.59,070612,,,A*60 $GPGGA,110730.000,4313.3418,N,02756.2409,E,1,06,1.4,164.7,M,37.0,M,,0000*59 $GPGSA,A,3,17,26,18,05,15,09,,,,,,,2.1,1.4,1.6*30 $GPGSV,3,1,11,26,82,234,40,28,70,055,,15,41,306,21,08,38,074,*7E $GPGSV,3,2,11,17,33,137,44,27,29,289,22,05,17,215,38,09,11,282,16*7E $GPGSV,3,3,11,18,07,324,25,07,03,091,,11,01,058,*45 $GPRMC,110730.000,A,4313.3418,N,02756.2409,E,0.00,248.59,070612,,,A*68 $GPGGA,110731.000,4313.3418,N,02756.2409,E,1,06,1.4,164.7,M,37.0,M,,0000*58 $GPGSA,A,3,17,26,18,05,15,09,,,,,,,2.1,1.4,1.6*30 $GPRMC,110731.000,A,4313.3418,N,02756.2409,E,0.00,248.59,070612,,,A*69 $GPGGA,110732.000,4313.3418,N,02756.2409,E,1,06,1.4,164.7,M,37.0,M,,0000*5B $GPGSA,A,3,17,26,18,05,15,09,,,,,,,2.1,1.4,1.6*30 $GPRMC,110732.000,A,4313.3418,N,02756.2409,E,0.00,248.59,070612,,,A*6A $GPGGA,110733.000,4313.3418,N,02756.2409,E,1,06,1.4,164.7,M,37.0,M,,0000*5A $GPGSA,A,3,17,26,18,05,15,09,,,,,,,2.1,1.4,1.6*30 $GPRMC,110733.000,A,4313.3418,N,02756.2409,E,0.00,248.59,070612,,,A*6B $GPGGA,110734.000,4313.3418,N,02756.2409,E,1,06,1.4,164.7,M,37.0,M,,0000*5D $GPGSA,A,3,17,26,18,05,15,09,,,,,,,2.1,1.4,1.6*30 $GPRMC,110734.000,A,4313.3418,N,02756.2409,E,0.00,248.59,070612,,,A*6C $GPGGA,110735.000,4313.3418,N,02756.2409,E,1,06,1.4,164.7,M,37.0
I want to read only the rows that contain %GPGSV in the beggining.So far i am using this code: serialObject = serial('COM6');
set(serialObject, 'BaudRate', 4800);
set(serialObject, 'Parity', 'none');
set(serialObject, 'ReadASyncMode', 'continuous');
set(serialObject, 'StopBits', 1);
set(serialObject, 'FlowControl', 'none');
fopen(serialObject);
data='';
while isempty(strmatch('$GPGSV',data))
data = fscanf(serialObject);
end
The problem is i receive only one row. Can you guys please help me receive a continuous string of data.
Also after acquiring only the %GPGSV rows i want to separate all the data between the commas.

4 个评论
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Walter Roberson
Walter Roberson 2012-6-16
I suggest replacing the fscanf() line with
data = fgetl(serialObject);
but that is more a matter of taste (fscanf() is designed for formatted reads but you are using it to get the entire line.)
Mihail Kolev
Mihail Kolev 2012-6-17
Ok but how to get fgetl() to read all the line but not just one
Mihail Kolev
Mihail Kolev 2012-6-18
Guys pls help i really need to complete this project.
I still can't get a continuous string out of the serial port.I can read only one line.
Walter Roberson
Walter Roberson 2012-6-18
Without getting into complicating details: Yes, you can only expect to be able to read one line at a time.
What happens on the second fgetl() ?

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