What do you mean NMEA codes? Can you please provide an example?
Also, have you tried testing the device with GPSInfo program (http://www.usglobalsat.com/store/downloads/GPSInfo.zip)?
You should be able to see the following NMEA sentences:$GPGGA,203901.000,2950.5123,N,09533.9439,W,1,11,0.9,32.5,M,-23.7,M,,0000*51
Just to confirm, is the red light blinking on the device or is it steady on? Or, is it completely off?
If you tested it with GPSInfo and you see garbage characters coming out, then, the device has possibly switched to SiRF mode (http://www.usglobalsat.com/s-131-terms-conditions.aspx#12
). To switch it back to NMEA mode, please refer to the instructions below:
1. Download and install this software: http://www.usglobalsat.com/store/downloads/SiRFDemo387.zip
2. Run the Sirf Demo software.
3. Connect your device, choose the correct COM port, and select the 4800 baud rate.
4. Go to Action > Open Data Source.
5. Next, go to Action > Synchronize Protocol & baud rate.
6. Then, go to Action > Switch to NMEA Protocol.
7. In the pop-up window, select the 4800 baud rate under the Baud Rate and click Send.
8. Close the Sirf Demo software.
Note: Be sure and not to click on anything else in this software, as you can render your device unusable.
Now, try your GPS Receiver with the GPSInfo Utility (http://www.usglobalsat.com/store/downloads/GPSInfo.zip
) to see if the problem persists.