The crystal oscillator circuit consists of two 30pf capacitors C2 and C3, and a 12m crystal oscillator x1. Here, the capacitance plays a role of vibration, which makes crystal vibration easier. Its value range is 15-33pf. The value of crystal oscillator can also be 24m. The value of crystal oscillator is related to the execution speed of single chip microcomputer. The higher its value is, the faster the execution speed of single chip microcomputer is. And in the circuit design, the closer the crystal oscillator is to the MCU, the better.