How to design a STM32 minimum system in hardware circuit design?

  The STM32 minimum system is mainly composed of STM32F103RCT6 microprocessor, clock crystal oscillator circuit, button reset circuit, power supply voltage regulator circuit and BOOT circuit. The microprocessor used in this minimum system is a 32-bit processor. Based on the high-performance RISC core, the operating frequency can reach 72MHz, and the operating voltage range is 2V to 3.6V. In addition, this type of MCU also has a 256K size Flash, which can be used for user data storage.

  The clock crystal oscillator circuit is composed of three parts: crystal oscillator, starting capacitor and feedback resistor. The crystal oscillator uses 8MHz passive crystal oscillator, which has excellent characteristics such as high precision, high frequency stability, and strong reliability. The input and output terminals of the crystal oscillator need to be connected with a resistor, which plays a role of generating negative feedback to ensure that the amplifier can work in the linear region of high gain, generally at the M ohm level, and 1 M ohm resistor is used in the circuit design of this system.

  STM32 series processors usually have three reset methods, namely: power-on reset, manual reset and program automatic reset. In the circuit design of the smallest system of the STM32 of this system, the reset circuit adopts a manual reset method, and the purpose of manual reset is achieved through the use of buttons. The processors of this series are low-level reset. When the button is pressed, the NRST pin and GND are turned on, and a low level is generated at this pin, thus realizing the reset of the single-chip microcomputer.

  The analysis of the power supply voltage regulator circuit is as follows. Since the power adapter used in this system provides a voltage source of 5V, the normal working voltage of the MCU used in the system is 3.3V, so the voltage source cannot directly supply power to the chip. Perform pressure reduction treatment. In order to reduce the 5V power supply voltage to the operating voltage of the 3.3V STM32 microcontroller, the circuit design uses AMS1117, a positive low-dropout regulator. The selected voltage regulator IC is the 3.3V step-down version of the AMS1117 series. Its output voltage accuracy is 1%, which meets the requirements of step-down accuracy. At the same time, due to its internal integrated overheat protection and current limiting circuit, it is A certain degree of security can be provided during use.

  There are other peripheral circuits. The four 104 capacitors need special attention when designing the PCB circuit. These filter capacitors must be passed through the several VCC/VSS terminals of the STM32 chip, otherwise it will cause the chip Consequences of not working.

  These 104 capacitors need to be connected first to achieve the effect of power supply filtering.