Overview
The project employs a sliding window for calculation of multiple frequency updates per second on this frequency counter and timer.
Explanation
During the operation, a 1Hz resolution up to 100MHz is being provided in the counter mode while the maximum resolution is 0.0000001Hz up to 1Hz in the timer mode. For each additional decade, the resolution is reduced by one digit. It uses an ATmega8 AVR microcontroller along with high-speed CMOS 4-bit counter 74HC93 and high-speed CMOS latch 74HC573. It also has 3 to 8 multiplexer 74LS138 and 16MHz crystal oscillator. The LEDs are driven by BC177 transistor but any PNP type can be used.
The 7 additional input bits are provided by the switch interface at the cost of only one Mega8 pin. For mode control switches, the inputs used consist of input select, method select, display select, and reserved for future extensions. A few modifications must be made in case the AVR should be programmable in circuit. The 47K resistors were used to isolate all third parties on wires used for programming. A low pass is created by the resistors in combination with Mega8 which is software compensated using increased settling time.
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