This is a design circuit for general theory of operation of this circuit and notes on frequency counting. This circuit is based on PIC microcontrollers for the main control unit of the circuit. This is the figure of the circuit;
The LCD is used in 4 bit mode interface so you only need 4 data lines and three control lines and it then fits into a single 8 bit port.
The crystal oscillator is simply a crystal and two capacitors connected to the PIC oscillator port at OSC1 and OSC2. The capacitors can both be fixed at the same value unless you want to tune it using a frequency reference. If you don't have an accurate reference then use fixed capacitors. The PIC micro can be any type that has a Timer 1 hardware and and has enough memory to hold the program. The LED is toggled at the end of every gate time to indicate that the processor is alive - so if there is no input signal you can tell that the software is working.
