I2C I/O Expander (FX18)



The FX18 is an I/O expansion controller designed to work with the BAC. There are an additional 16 I/O ports. There are two high output ports, which can be used to provide up to 2A of output current. The FX18 communicates to the BAC via an FX45 using I2C. There is a Hi-Drive I2C terminal allowing the FX18 to be considerable distance from the BAC & FX45.


  • 16 x I/O port
  • 14 x Individually configurable port; Output, Input, Input Pullup, Input Pulldown
  • 2 x Output port: Can be used standard, or 2A high current mode
  • Optional keypad ribbon cable header
  • Optional storm keypad 8 pin header
  • Hi-Drive I2C terminal
  • I2C Input/Output port


  • Header J1 (I2C Hi Drive / Power)
  • Header J2 (2A Output)
    • Pin 1 → GND
    • Pin 2 → Source Output, Controlled by IO 15 
      • supplies DC voltage from pin 4 of J2 (12-24 VDC)
    • Pin 3 → Source Output, Controlled by IO 16
      • Supplies DC voltage from pin 4 of J2 (12-24 VDC)
    • Pin 4 → VDC Input, (12-24 VDC)
      • Use power supply with minimum of 2 A supply current
  • Header J8 (Ribbon Cable Keypad)
    • Pin 8 is unused
  • Header J9 (Telephone Keypad)

Keypad Wiring: