This challenge lets you create a frequency counter with wonderful precision and low consumption because of using a 32768Hz quartz.
The challenge is predicated on a BluePill with STM32 microcontroller. The latter receives a 10MHz clock which is multiplied to 70MHz by the inner circuit of the microcontroller and makes use of a 32768Hz clock to depend the pulses. Due to the precision of the quartz at 10MHz and the inner compensation circuit, the clock at 32768Hz will probably be corrected so as to receive wonderful precision. Alternatively, a DS3231 might be used which has an output clock on the identical frequency however temperature compensated.