XBee 802.15.4 RF Modules. XBee S2C 802.15.4 RF modules are built with the Silicon Labs EM357 SoC by Digi International. The design has improved power consumption, support for over-the-air firmware updates and provides an upgrade path to DigiMesh or ZigBee mesh protocols. Also provides a long-range line-of-sight communication for up to 1200 m or 3200 m. Features. Serial Data Interface UART, SPI Configuration Method API or AT commands, local or over-the-air (OTA) Frequency Band ISM 2.4 GHz Form Factor Through-Hole, Surface Mount Hardware S2C ADC Inputs (4) 10-bit ADC inputs Digital I/O 15 Antenna Options Through-Hole: PCB Antenna, U.FL Connector, RPSMA Connector or Integrated wire SMT: RF Pad, PCB Antenna or U.FL Connector Operating Temperature -40º C to +85º C