Concept ：

What is the smallest system ？

Minimum system refers to ： To be able to make MCU The smallest unit of work ;

structure : Intraslice / Peripherals on the film 、 Peripherals on the board ;

Roughly as above ： The special unit is like the reset circuit on the right 、 Concussion circuit , It is called circuit on board . Add on-chip peripherals , Composition chip .

What are the minimum system components ？

1. Power part

    The chips currently used are COMS level （3.3V Power supply ）;

2. Oscillating circuit

  To be able to make MCU The circuit that generates the working heartbeat . Generally, there are many kinds of such circuits , such as RC oscillator 、 Crystal oscillator, etc ;

3. Reset circuit

  Concept ： To be able to make MCU From again main The circuit in which the function begins to execute ; Generally, such reset circuits can be divided into many kinds ： For example, software and hardware reset 、 watchdog （WDG） Reset and so on ;

The main thing to master is hardware reset ： The peripherals on the board can make MCU Reset circuit . such as ： Your board is stuck , You need a button to reset the board and start working again , Such a circuit , It becomes hardware reset . for example ： The reset button .

Reset circuit

  Of course , Hardware reset can also be divided into high and low levels , When it can make MCU The reset high level becomes the high level reset ; Be able to make MUC The low level of reset is called low level reset .

4. Starting mode .

STM32F40x There are many ways to start the chip , You can choose according to your own needs ;

explain ： When BOOT1:BOOT0 by X 0 When , At this time, the startup mode is   From the main Flash start-up ,MUC It can work normally ;

          When BOOT1:BOOT0 by 0 1 When , At this time, the startup mode is Boot from system memory , But the program can be burned , But can't carry out ;

           When BOOT1:BOOT0 by 1 1 When , At this time, the startup mode is From embedded SRAM start-up , And the program can be burned and code executed ; But when you press the reset button , The program will not execute , Code will be lost , Because when you press the reset button , The power supply will be cut off , Therefore, the code program will also be lost .

therefore , The chip （STM32F407ZGT6 For example , Series chips are similar ） The best thing to use is X0 The way to start . Of course , When the program download fails to operate due to some error , You can adjust the startup mode , In this way, you can download and burn later .