Basic board to create, in combination with the FT1308M and FT1128M (not included), a complete GPRS modem to make data connections, calls, send sms. For example, it allows the use of GPS / GSM or GSM-only locators in point-to-point mode so as to instantly obtain positioning data and then follow movements directly. It allows direct data connections with another modem or mobile phone equipped with a modem, but without going through the web: connections are made directly on the GSM data channel. The board has a socket for a loudspeaker and one for a microphone with which, for example, establish communication. The module is interfaced with a USB converter capable of allowing its management and communication through any USB port on a computer, tablet or device that has the host-type USB interface, including many types of microcontrollers. The module that realizes the GSM / GPRS connection and therefore the heart of the modem is to be chosen from the 3 modules indicated above, which can be used both for Internet access and for voice communication (as long as you connect a microphone and a small speaker) and SMS .

The module that makes the GSM / GPRS connection and therefore the heart of the modem is the SIM800C of SIMCom: it is one of the most recent Quad-band GSM / GPRS compatible cellular modules, operating on the frequencies of 850/900/1800 / 1900MHz, can be used both for Internet access, both for voice communication (provided you connect a microphone and a small speaker) and SMS. Externally it comes in a large package 24mm x 24mm x 3mm with contacts placed on the four sides and L-shaped so that they can be welded to the side and below. The module is internally managed by an AMR926EJ-S processor that manages telephone communication, data communication (via an integrated TCP / IP stack) and dialogue (via a UART and a TTL serial interface) with the circuit to which the mobile phone interfaces .

The processor also takes care of managing a 3 or 1.8 V SIM to be mounted outside the module.

• GSM / GPRS module: SIM800C
• Frequency band:
  - Quad band: GSM 850, EGSM 900, DCS 1800, PCS 1900. The 4 frequencies can be searched automatically, or set via the AT command "AT + CBAND".
  - Compliant to GSM Phase 2/2 +
• GPRS connectivity: multi-slot class 12 (default)
• Transmission power:
  - Class 4 (2 W) to GSM 850 and EGSM 900
  - Class 1 (1 W) to DCS 1800 and PCS 1900

• SIM800C data sheet