The SIM808 module is a combined GPS receiver and GSM cellular/mobile transceiver. (Datasheet)

In this step, we will enable and explore the GPS receiver functionality.

WIRING: As shown, the SIM808 is wired to the serial port of the WeMos D1 Mini (or most any microcontroller) using three lines: RX, TX, and GND. The pins in the diagram correspond to the same code below. The 5V Power and Ground can be supplied from any high quality USB power bank or adapter using the included MicroUSB breakout. A bench power supply or similar supply can also be used. Do not try to power the SIM808 from the WeMos D1 Mini.

ANTENNA: Connect the GPS Antenna via its 1m SMA ccable to one of the SMA to uFL/IPX coaxial adapter cables. Connect the uFL/IPX end of the adapter cable to the coaxial connector on the SIM808 module marked GPS.

SATELLITES: Power up the SIM808 with the GPS Antenna connected. The RED LED (power) will come on. After a couple of minutes four (or more) GPS satellites should be acquired and the BLUE LED on the SIM808 will start blinking slowly.

SAMPLE CODE: Use the Arduino IDE to program the GPSdemo.ino example code into the WeMos D1 Mini. The Arduino Serial Monitor can be used to observe the time and position information determined by the GPS receiver. For example:

"1,1,20191001155512.000,36.118994,-115.167543,119.400,1.06,94.9,1,,1.1,1.4,0.8,,7,7,,,39,,"

Note that the field starting with the year (for example, 2019) can be broken down as a date/time stamp (in UTC). The next two fields are latitude and longitude. These can be pasted into a google search box for mapping to verify your location. Test the lat/long in the example string above for a map to DEF CON 28 in August 2020.