Andy Brown was working with embedded project where he needed to test oscillator accuracy. The first thought was to grab frequency counter on eBay and continue working. Bus somehow he ended up building his own counter with great characteristics and Android connectivity.
He used FPGA to do the counting. FPGA is faster comparing to MCU. Its hardware like nature and parallel operations allow reacting to incoming signals much faster than MCU would do. He included STM32 microcontroller in his built to take care of logging and connectivity with external world. His frequency counter is able to precisely measure frequencies up to 50MHz. He took special care when designing reference oscillator, because the accuracy of counting depends on it. He built a prototype four layer board which includes Bluetooth module for Android connectivity. In custom Android program he is able to customize meter settings and see all measuring process in numerical and graphical form.
We recommend EasyEDA for circuit design and PCB prototype