Theta Engineering did the circuit design, circuit board artwork design and the low-level firmware development for a new generation of the Knox Sentralok key release system. This project utilized three firmware developers and an electronics engineer. Numerous technologies were involved:
- C code development on the MSP430 microcontroller
- 10-year lithium-powered real-time clock implemented using the MSP430 and taking advantage of its low-power features and dual-crystal capability (one high-speed crystal for normal operation and one 32KHz watch crystal for time keeping).
- MSK Modem. MSK stands for "Minimum Shift Keying". It is a form of audio modulation optimized for data transmission over analog radios.
- DTMF detection and transmission. "Dual Tone Multi-Frequency" signaling is what you hear every time you dial a touch-tone phone.
- Infrared communications using IrDA-type transmitters and receivers
- Serial flash memory
- Security and encryption through the use of Dallas Semiconductor's SHA-1(Secure Hash Standard) devices
- LCD/keypad/beeper user interface
- RS-232 communications