A Simple, Low Cost and Multiple Input Alarm System, Functioning as Finite State Machine (FSM), Using VHDL and FPGAs
Evangelos I. Dimitriadis and Leonidas Dimitriadis
An FPGA based alarm system, available of using unlimited number of inputs was programmed and put in use, in this work. A low cost FPGA RZ Easy A 2.2 was used, with its four dip or button switches acting as inputs. As soon as one or more switches are ON (bit 1), the respective LED lights on, while at the same time, seven segment display shows the number of ON state inputs, corresponding, for example, to the opened doors of a house. Simultaneously the buzzer clock algorithm is activated leading buzzer to sound. If all switches go manually to OFF state (bit 0), then all LEDs are off, buzzer stops sounding and seven segment display shows zero, thus indicating for example, that no house entries are open. The above function resembles a finite state machine, since the output state, depends on the inputs of the system. The VHDL code of our system gives the opportunity of having no limitation on the number of inputs and also the ability of changing the ringing rate of the buzzer.
Keywords: FPGA, VHDL, alarm system, finite state machine