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Punch in the third day .

2022/2/15　 Basic class section III training .

The main content is ： Single chip microcomputer clock tree ,STM32CubeMX Configure clock 、STM32 Of GPIO The output mode 、 The input mode .

1、STM32F103 Yes 4 The clocks are ：HSE High speed external clock ,HSI High speed internal clock ,LSI Vulgar internal clock ,LSE Vulgar external clock .

2、STM32CubeMX Configure clock

 （1）、 First click on RCC stay High speed clock（HSE） Drop down to select Crystal/Ceramic Resonator Enable external clock , Enabled on the simulation chip diagram on the right 2 A pin will light up RCC_OSC_IN、RCC_OSC_OUT.

（2）、PPL choice 9 frequency doubling APB1 choice /2 Recommended configuration for

（3）、STM32CubeMX Screenshot and analysis of the configured bus clock file

 （4）、GPIO Can make

 3、STM32 Of GPIO The output mode ： Push pull output 、 Open drain output 、 Multiplexing push pull output 、 Reuse open drain output

（1）、 Push pull output is used MOS control IO High and low output of .

（2）、 Open drain output utilization MOS control IO Low level output of , High level is controlled by internal pull-up resistor . Or an external pull-up resistor It can be 5v It can also be 3.3v.

 （3）、 The output of the multiplexing function is to control the columns externally, such as I2C

4、STM32 Of GPIO The input mode ： Pull up input 、 Drop down input 、 Floating input 、 Analog input .

 （1）、 Up and down input is control 2 Up and down switches , When it is set as pull-up input , Internal pull-up switch , On if there is an external low level, then ,IO What I read originally is that the high level changes to the low level

（2）、 Floating input is 2 Both switches are off , here IO Belongs to an unknown state .

（３）、 The analog input is to TTL Schottky trigger off , The signal passes directly from the analog input ADC The controller analyzes the simulated values .