Making high precision frequency counter by GPS trained clock

A project log for How to get high precision frequency standard ?

Now the time to get high precision frequency standard less than $10!

kodera2tkodera2t 09/21/2018 at 08:470 Comments

Here just jumping to the result, but I've succeeded to make the frequency counter, driven by GPS trained clock (8MHz). The original 8MHz Arduino (Arduino Pro/mini) utilizes internal RC 8MHz oscillator and I re-write fuze bit for crystal oscillator. The reason why not "external clock source" but "crystal oscillator" is for switch-ability bbetween internal crystal clock operation and GPS clock. Just disconnect X1 terminal of crystal and injecting GPS single instead, AVR works under GPS clock.

For frequency counter implementation, I utilized a library at

Just we need to change pre-scaler of register for 8MHz clock operation, as

In addition, I added rotary encoder for gate timing switch and OLED display as shown in the above image. Indeed the image shows the measurement of 1MHz generated by another GPS module. Independent two GPS module has encounter the same result ! (I am not sure if GPS is not accurate, but I guess we can believe.)