XPC target serial communication NMEA

I'm trying to read the data send by a NMEA compass on my Xpc target PC. I've read the tutorial from Gordon Weast about this, but unfortunately my model doesn't work.

The compass sends the following sentence 10 times a second: $HCHDG,hhh.h,,,,*ss<CR><LF>, where hhh.h is the heading (eg 180.0 means south). Serial output is RS422, 4800 Baud, 8 data bits, 1 stop bit, no parity.

When I open the com1 port in matlab and use the fscanf command, I receive the following:

>> fscanf(ser)

ans =

$HCHDG,43.6,,,,

So I suppose the com port and compass are working fine.

The problem is, I only receive zeros.

In my model I'm using the Baseboard Serial F board, connected with the FIFO ASCII read block. This FIFO block is only sending zeroes as I saw on the scope I connected. Any idea what is wrong?