Fitlet3 How to use GPS features of Sierra EM7421 modem

• This application note applies to fitlet3 configured with Sierra EM7421 cellular modem.
• It explains how to use the GPS feature

The EM7421 includes three RF connectors for use with host-supplied antennas:

	Main RF connector — Tx/Rx path
	GNSS RF connector — Dedicated GPS, GLONASS, BeiDou, Galileo, and QZSS
	Auxiliary RF connector — Diversity, MIMO, GPS, GLONASS, BeiDou, Galileo and QZSS

To get the GPS working via the GNSS RF connector:

	1. Unplug the connector from the Auxiliary RF connector 
	2. Connect it to GNSS RF connector.

To get the GPS working via the Auxiliary RF connector (Diversity antenna) - change the modem configuration:

1. Unlock password protected AT commands

	echo -ne 'AT!ENTERCND="A710"\r\n' > /dev/ttyUSB3

2. Set the autostart for GPS

	echo -ne 'AT!GPSAUTOSTART=1\r\n' > /dev/ttyUSB3

3. Set the GPS antenna to the aux port (diversity), where is the antenna connected, because by default: the "gnss rf" port is selected in the modem configuration.

	echo -ne 'AT!CUSTOM="GPSSEL",1\r\n' > /dev/ttyUSB3