Hal library IIC simulation in punctual atom STM32 `define SDA_ IN() {GPIOB-＞MODER＆=~(3＜＜(9*2))；GPIOB-＞MODER|=0＜＜9*2；}` // PB9 input mode

The punctual atoms hal Library simulation iic Involved in the
#define SDA_IN() {GPIOB->MODER&=~(3<<(9*2));GPIOB->MODER|=0<<9*2;} //PB9 The input mode

#define SDA_OUT() {GPIOB->MODER&=~(3<<(9*2));GPIOB->MODER|=1<<9*2;} //PB9 The output mode

stm32 In the Chinese reference manual I/O Port control register Is explained as follows ：

Every GPIO Yes 4 individual 32 Bit memory mapped control registers （ GPIOx_MODER、 GPIOx_OTYPER、GPIOx_OSPEEDR、 GPIOx_PUPDR）, Can be configured up to 16 individual I/O. GPIOx_MODER Registers are used to select I/O Direction （ Input 、 Output 、 AF、 simulation ）. GPIOx_OTYPER and GPIOx_OSPEEDR Registers are used to select the output type respectively （ Push and pull or open the leak ） And speed ( Whatever kind of I/O Direction , Will directly put I/O The speed pin is connected to the corresponding GPIOx_OSPEEDR Register bit ）. Whatever kind of I/O Direction , GPIOx_PUPDR Registers are used to select pull up / The drop-down .

GPIO Port mode register (GPIOx_MODER) (x = A…I) Here's the picture

The value of the register can be modified by software , To decide I/O The direction of .

The first part GPIOB->MODER&=~(3<<(9*2)); Is decimal 3（ Binary is 11） Move left （9*2） bits , Also is to 18,19 Set the position to 11, And then the reverse becomes 00, And again GPIOB->MODER And operation , here GPIOB->MODER Of 18,19 A into 00. The first sentence is to GPIOB->MODER Of 18,19 Location 0. here PB9 Is the input mode
Rear part GPIOB->MODER|=0<<9*2 and GPIOB->MODER|=1<<9*2 That is, assign values to these two positions according to the input and output of the reference manual , The process is the same as above .

There is also a method of standard library Register operation port mode #define SDA_IN() /#define SDA_OUT()（ The punctual STM32-IIC experiment ）