A hybrid analog/digital circuit for experiments in controlling chaos

This paper describes a hybrid analog/digital circuit consisting of a chaotic oscillator, an analog-to-digital (A/D) converter, and a digital-to-analog (D/A) converter. The A/D converter is used to sample the oscillator output while the D/A converter generates a control voltage to drive the oscillator. Both the A/D and D/A converters are controlled by an external processor through a digital interface. Two external processors have been used: a personal computer via a parallel port and a Texas Instruments (TI) digital signal processing (DSP) board via an external memory interface. As an example application, a board containing multiple copies of this circuit was used to synchronize two chaotic oscillators as proposed in Jankowski et al. (Int. Journal of Electronics, vol. 79, pp. 823-828, 1995). The resulting system is readily reconfigured to sample and generate external signals. Example C code for the TI DSP processor is included.