The concept of this board is to build an open, very versatile frequency counter, so it can be used to measure a wide variety of signals. It is designed to be customizable in every possible way.
Freq_LF_HF v1.0 board uses the famous AVR microcontroler Atmega328p-AU. This is not the newest ATMEL model but this chip is standard on Arduino UNO v3.0 board. It is a powerfull microcontroller and very small (TQFP- 32). This gives the opportunity for users to benefit from the Arduino community support and the many software libraries. The firmware uses a couple of the wonderfull functionnalities of this chip, namely the 16 bits timer, interrupts and comparator to an external precision voltage reference.
Arduino compatible high precision frequency counter – [Link]