Adafruit FONA 808 Mini Cellular GSM + GPS Breakout

Power the FONA 808 via its JST PH connector using a single-cell 3.7V LiPo battery (3.7V-4.2V range). For stable operation during cellular transmission peaks, ensure your power source can deliver at least 2A. The onboard regulator and logic level shifters allow the serial control pins to interface safely with 3.3V or 5V microcontrollers like Arduino or Raspberry Pi GPIO.

You need two external antennas: a quad-band GSM antenna and a passive GPS antenna, both with uFL connectors. Screw the uFL pigtails firmly onto the board's labeled ports. For best GPS reception, place the GPS antenna with a clear view of the sky. The GSM antenna's placement affects signal strength; an external magnetic mount antenna on a metal surface often significantly improves network registration and data reliability.

Connect the module's TX and RX pins to your microcontroller's UART, using a logic level converter if needed. Power on the module and open a serial terminal (e.g., 9600 baud). The FONA 808 supports auto-baud detection. Start with basic AT commands like 'AT' to check communication, 'AT+CSQ' for signal strength, and 'AT+CGPS=1' to power the GPS. Refer to the SIM808 AT command manual for detailed instructions on calls, SMS, and GPRS data setup.

Yes. After inserting an active SIM card and establishing a network connection (AT+CGATT=1), you can use GPRS to open a TCP or UDP socket. Use commands like 'AT+CIPSTART' to connect to your server's IP and port, then 'AT+CIPSEND' to transmit data. For HTTP, you can send raw HTTP GET/POST requests. Ensure your mobile carrier supports GPRS data and that any APN settings (configured via AT+CSTT) are correctly entered for data access.

Time-To-First-Fix (TTFF) varies from 30 seconds to a few minutes, depending on satellite visibility and whether a recent almanac is cached. For a 'hot start' with valid ephemeris data, fixes can be under 10 seconds. Ensure the GPS antenna has an unobstructed view. Using the command 'AT+CGPS=1,1' enables assisted GPS (A-GPS) mode if supported by your network, which can dramatically reduce TTFF by downloading ephemeris data via the cellular connection.