How to extract only '$GPGGA' string real-time from Garmin gps device on matlab ?

Hello, I am trying to extract GPS signals real-time from a Garmin 18x device by using serial communication. But every time I run the program using a 'while' loop, there are other strings namely '$GPVTG' and '$PGRME' also being read. I just need '$GPGGA' string for my use case which I'm not able to extract.

I did try using 'textscan' and 'strtok' but nothing worked as there are 3 different string types and lengths. The command window showing the string data being read is as shown in the image.

The code I used is below:

% Extraction of data from GPS

garmin_gps = serial('COM4','Baudrate', 19200); %Create serial port object 'garmin_gps' to connect Garmin device

set(garmin_gps, 'InputBufferSize', 512000);

set(garmin_gps, 'terminator', '*')

fopen(garmin_gps);

Z = isempty('InputBufferSize')

while Z == 0

D = fscanf(garmin_gps, '%s')

end

Answer 1

[Mark McBroom]

Have you tried regexp?

[Prajwal Ramakrishna]

Yes, But then it returns just the index values of the expression I require. In my case, I only need the '$GPGGA' string omitting the other two when the 'while' loop iterates every time. Please help me with this.