Detailed explanation of STM32 minimum system circuit

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Detailed explanation of STM32 minimum system circuit [Copy link]

STM32 minimum system hardware composition

The minimum system is the minimum requirement for the operation of the microcontroller. It does not include peripheral control and has a simple principle. Analyzing the minimum system is the basis for getting started with STM32.

composition:

· power supply

Reset

· clock

Debug /download interface

· start up

power supply

The 3.3V power supply is connected here, and the capacitor acts as a filter.

Reset Circuit

When the RESET pin is pulled low to generate an external reset, a reset pulse is generated to reset the system.

There are three reset methods:

Power - on reset

Manual reset

· Automatic program reset

Power-on reset : At the moment of power-on, the capacitor is charged and RESET appears a short low level. The duration of the low level is determined by the resistor and the capacitor. The required reset signal duration is about 1ms. The calculation method is as follows:

t = 1.1RC (fixed calculation formula)

1.1*10K*0.1uF=1.1ms

Manual reset : When the button is pressed, RESET is connected to the ground, thus generating a low level to achieve reset.

clock

The function of the crystal oscillator is to provide the most basic clock signal for the minimum system, and the function of the capacitor is to ensure that the oscillation frequency output by the crystal oscillator is more stable.

BOOT startup circuit

The BOOT0 and BOOT1 pins of the STM32 chip can use jumper caps to set their levels to control the startup mode of the chip. It supports startup from internal FLASH, system memory, and internal SRAM.

Generally, JTAG or SWD is used to debug and download the program, which will be downloaded to the flash memory, so the BOOT0 pin and BOOT1 pin can be directly set to a low level.

The storage media corresponding to the three startup modes of STM32 are all built-in to the chip, they are:

User Flash = Flash built into the chip.

· SRAM = The RAM area built into the chip, that is, the memory.

System memory = A specific area inside the chip. A Bootloader is preset in this area when the chip leaves the factory, which is usually called the ISP program. The content of this area cannot be modified or erased after the chip leaves the factory, that is, it is a ROM area, which uses USART1 as the communication port.

Debug interface

STM32 has two debugging interfaces, JTAG is 5-pin and SWD is 2-wire serial (four wires in total)

In addition, USB is used for program burning and data output: connecting to the computer USB port can also provide power for small load driving.

Usually the CH340G chip is used to realize USB to serial port conversion. Use this chip to map the computer's USB to a serial port. Note that the serial port driver should be installed on the computer, otherwise it cannot be recognized normally.

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huo_hu

The minimum required is vcc.

qwqwqw2088

Generally, the BOOT0 and BOOT1 jumpers of the startup circuit should be set to 0 (ground).