Fax Control Board

Theta Engineering did circuit design and firmware development of two generations of a Fax Control Board used as the in-room portion of a system that allowed automated fax delivery directly into a hotel guest’s room. This first-generation device utilized a 16-bit Motorola microcontroller from the 68HC12 family. It replaced the "LIU" (Line Interface Unit) of an HP All-In-One fax/printer/scanner, providing the ability to monitor machine usage and to communicate with the system's server for billing purposes. This design included a novel telephone line-voltage monitoring circuit that enabled the microcontroller to monitor the phone line without violating FCC requirements.

This second generation Fax Control Board utilized an MSP430 microcontroller from Texas Instruments, as well as a Xilinx CPLD and a serial flash memory. It was used in Canon multi-function printer/fax machines, replacing the original board that was used to receive the phone line. This design also inserted itself between the printer's main logic board and the printer's front panel, allowing the machine's "user interface" to be modified to satisfy certain requirements of the hotel application.

This project included development of a two-way communications protocol based on DTMF signaling, development of complex state machines in firmware for tracking and reporting fax machine activity, numerous diagnostic and maintenance features, and supporting software written in Visual Basic. FCC certification was obtained for both these devices.