One 、GPIO working principle

Prepare information

• 《STM32 Chinese Reference Manual 》 Chapter viii. ： Common and reusable functions I/O(GPIO and AFIO)

• 《 Chip data book （datasheet）》 Official website address https://www.stmcu.com.cn/Product/pro_detail/STM32F103/product
  

• 《STM32 Incomplete manual - Library function version 》

• 《STM32 Incomplete manual - Register version 》

1.1、GPIO Basic structure and working mode

1.1.1 Basic structure description

My board is 64 Pin
Chip data manual page 19 page

STM32F103RCT6
4 Group IO mouth 16*3+2=51 One pin ：

• GPIOA0-A15
• GPIOB0-B15
• GPIOC0-C15
• GPIOD0-D2
  IO The port can also be connected to peripherals
  Chip data manual page 23 page
  PA9,PA10 It's also a serial port 1 Pin
  
  GPIO The basic structure ：
  Chinese reference manual page 105 page
  

1.1.2 Working mode

4 Input mode ：

• Enter the float
  

• Input pull-up
  

• Type in the dropdown
  

• Analog input
  

4 Output mode ：

• Open drain output
  （1） Output 1 when ：
  

（2） Output 0 yes ：

• Open drain multiplexing function
  This output 1 Or 0 The situation is basically the same as that of open drain output , The difference is that the output data is obtained by the peripheral
  

• Push pull output
  (1) Output 1 when ：
  

(2) Output 0 when ：

• Pull back multiplexing function
  The pullback multiplexing function here is basically the same as that of the previous open drain , The following output methods are the same , But the previous output source is different .
  
  Be careful ：
  Open drain output ： It can output high and low levels , Connect digital devices
  Open drain output ： Only strong low level can be output , High level needs to be pulled up by external resistance . The output end is opposite to the collector of the triode , To get a high level, you need to pull up the resistor , It's suitable for current drive , Its ability to absorb current is relatively strong （ commonly 20ma within ）

3 Maximum turning speed ：

• 2MHZ
• 10ZHZ
• 50MHZ

1.2、GPIO Register description

Each group GPIO Port registers include ：
Two 32 Bit configuration register （GPIOx_CRL,GPIOx_CRH）
Two 32 Bit data register （GPIOx_IDR,GPIOx_ODR）
One 32 Position position / Reset register （GPIOx_BSRR）
One 16 Bit reset register （GPIOx_BRR）
One 32 Bit lock register （GPIOx_LCKR）
Chinese Reference Manual 113 page

Chinese Reference Manual 114 page

Chinese Reference Manual 115 page

1.3、STM32F10x GPIO Pin description

（1） Port multiplexing function
What is reuse , Simple understanding , It's just that a man's language talent is very good , chinese 、 english 、 Korean 、 He can speak Thai , His boss, Mr. Hui, can only speak Chinese , But the business is very big , Running all over the world . Just hire him as an interpreter . When the boss goes to England on business , He translated English for the boss ; When the boss goes to India on business , He translated Thai for his boss , This function is configured by him , Then he will translate whatever language the boss wants him to translate , and STM32 Of IO What functions does the port have? We can find it in the chip data manual , Then you are its boss , If you want him to realize what function, he can realize what function ！
The biggest function of reuse is to maximize the use of IO Oral resources ！！！ And the boss wants to hire employees who know everything ！
Chip data book 30 page

（2） Port remapping function
What is port remapping , President Hui is on a business trip to Sanya , I didn't expect to meet a Malaysian customer , I really want to order the products of Hui head office , But this man speaks Malay , And President Hui didn't take Daxiong on this business trip , But only the Secretary Xiao Lan , So Xiaolan Weihui always said through an idea , President Hui and I are on a Bluetooth phone , Then you communicate with customers , I'll act as your interpreter temporarily , Communicate with customers . In the process , Xiao Lan uses certain technical means to translate Da Xiong's translation function , Give it to yourself temporarily , Is to realize the remapping of translation function , about IO Mouth is the original A9,A10 Serial port 1 function , From new mapping to PB6,PB7 Pin .
Chip data book 33 page

Chip data book 35 page