Andy published his accurate and open source frequency counter that uses an Android phone as a display. It’s based on a high accuracy temperature compensated crystal oscillator (TCXO) fed into a phase locked loop (PLL) to create a high frequency reference clock. The reference clock along with the input signal is processed by a Xilinx FPGA and a STM32F072 mcu is reading the data.
Here we have a good example of how a requirement for a simple tool spirals out of control and spawns a project that takes months to complete and ends up dwarfing the project that it was originally expected to facilitate. You see, some time ago I was fiddling around with a project, something to do with data logging, probably, I’ve actually forgotten what I was up to.
Nanocounter: Frequency Counter with an Android Interface – [Link]