GPIO port details, Hal library operation keys

This blog knowledge comes from Mr. Wei Dongshan's 7 Internet of things course .

One 、GPIO Detailed explanation

1、STM32F103C8T6 Altogether 48 One pin .

2、 Press A、B、C grouping , Each group 16 One pin , The number is 0~15,STM32F103C8T6 Yes 2 Group GPIO, Each group has 16 One pin , namely 32 individual GPIO Pin .

3、GPIO Working mode

STM32F103 Series of I/O The pins share 8 Working mode , There are four output modes ： Push pull output 、 Open drain output 、 Multiplexing push pull output 、 Reuse open drain output ; There are four input modes ： Pull up input 、 Drop down input 、 Floating input 、 Analog input .

• Push pull output （ Push-Pull, PP）

        The push-pull structure consists of two MOS The tubes are connected in a complementary and symmetrical manner , At any time, one of the triodes is always on , The other triode is off . Pictured above 1 Shown , The interior consists of a P-MOS Tube and a N-MOS Tube composition , Two MOS The grid of the tube （ Gate, G） To the left “ Output control ” , Drain electrode （ Drain, D） Connected to external output , P-MOS The source of the tube （ Source, S） Receive VDD（ 3.3V）,N-MOS The source of the tube is connected to Vss（ 0V）.

        MOS The tube is used as a switch ,“ Output control ” To two MOS Apply a certain voltage to the tube grid , P-MOS Conduction between the source and drain of the tube ,VDD after P-MOS Tubular S->G->D Output , N-MOS The tube is in a high resistance state （ The resistance is very high , Approximate open circuit ）, The overall external is high level ;“ Output control ” Cancel to two MOS Apply voltage to the tube grid , P-MOS Tube source and grid cut-off , P-MOS The tube is in a high resistance state , N-MOS The source and drain of the tube are connected , The overall external is low level .
        MOS The tube is used as a switch ,“ Output control ” To two MOS Apply a certain voltage to the tube grid , P-MOS Conduction between the source and drain of the tube ,VDD after P-MOS Tubular S->G->D Output , N-MOS The tube is in a high resistance state （ The resistance is very high , Approximate open circuit ）, The overall external is high level ;“ Output control ” Cancel to two MOS Apply voltage to the tube grid , P-MOS Tube source and grid cut-off , P-MOS The tube is in a high resistance state , N-MOS The source and drain of the tube are connected , The overall external is low level .

• Open drain output （ Open-Drain, OD）

         In open drain mode ,“ Output control ” Will not control P-MOS tube , “ Output control ” Only to N-MOS Apply a certain voltage to the tube grid , Two MOS All tubes are in the cut-off state , The two drains are suspended , It's called open drain .“ Output control ” Cancel the applied voltage of the grid , PMOS The tube is still in the high resistance state , N-MOS The pipe is open , The overall external is low level .    

         The open drain output mode can be equivalent to P-MOS The tube is regarded as nonexistent . That is, only low level can be output in this mode , To output high level , External resistance is required , The connected resistance is called pull-up resistance , At this time, the output level depends on the external power supply voltage of the pull-up resistor , As shown in the figure above, red VCC+ External circuit of resistance .

         Push pull output mode can directly output high level , Open drain output mode requires external pull-up resistor to output high level , But the open drain output has some characteristics that the push-pull output does not have ：
        ① Using external circuit driving capability . As shown in the figure above ,“ Output control ” Only a small gate drive current is required , VCC Increase the driving current for the external load through the pull-up resistor ;
        ② Realize level conversion . The push-pull output mode consists of VDD Provide , That is, only 3.3V level . After using the open drain output mode , VCC It can be for 5V, Thus, the effect of level conversion is realized .

        ③ Easy to implement “ Logic and ” function . Multiple open drain pins can be used directly together , Connect a suitable pull-up resistor uniformly , Can be realized “ Logic and ” Relationship , That is, when all pins output high level , The output is high level , If any pin outputs low level , Then output low level . stay I2C、 SMBUS And other bus circuits are often used .

        VCC Can connect 5V/3.3V, Improve the driving ability of pins , I think the internal structure of the chip is very thin , The current that can pass through is limited , Add a thick circuit outside to connect , It can drive a large current . If VCC yes 5V It can realize the function of level conversion , Because normally ,IO The output is 3.3V.

• Reuse function push-pull / Open drain output （ Alternate Function, AF）

        GPIO In addition to being a general-purpose input / The output pin uses an external pin , It can also be used as an on-chip peripheral （ USART、 I2C、 SPI etc. ） Dedicated pin , That is, one pin can be used for many purposes , But one pin can only use one of the multiplexing functions at the same time .
         When the pin is set to the multiplexing function , The multiplexed push-pull output mode or multiplexed open drain output mode can be selected , When set to multiplex open drain output mode , It needs to be connected with pull resistance .

• Pull up input mode （ Input Pull-up）

         As shown in the figure above , VDD Through the switch 、 Pull up resistance , Connect external I/O Pin . When the switch is closed , external I/O When there is no input signal , The default input is high . The typical application of this mode is the external key , When no key is pressed , MCU The pin of is the determined high level , When the key is pressed , The pin level is pulled to low level .

• Drop down input mode （ Input Pull-down）

         As shown in the figure above , Vss Through the switch 、 Pull down resistance , Connect external I/O Pin . When the switch is closed , external I/O When there is no input signal , The default input is low . The typical application of this mode is also the external key , When no key is pressed , MCU The pin of is the determined low level , When the key is pressed , The pin level is pulled high .

• Floating input mode （ Floating Input）

         As shown in the figure above , Two up / The pull-down resistance switches are disconnected , Neither pull-up nor pull-down , I/O The pins are connected directly TTL Schottky barrier
trigger , here I/O The pin is floating , The reading level is uncertain , What level is the external signal , MCU The pin inputs what level . MCU Reset after power on , The default is floating input mode .

• Analog input mode （ Analog mode）

        As shown in the figure above , Two up / The pull-down resistance switches are disconnected , meanwhile TTL The Schottky trigger switch is also off , The pin signal is directly connected to the analog input , Realize the acquisition of external signals .

Two 、cubeMX Set up GPIO

1、 Choose one first GPIO, The choice here is PA1 For export .

2、 Click on the left GPIO.

3、 Click... In the middle PA1 Options , Then you can set PA1 Detailed parameters of .

4、 Here you can set the default output level 、 The output mode 、 Whether to pull up or down 、 The frequency of the clock is high, medium and low .

 5、 It can be for PA1 Set an alias , Here we take LED. In the code, it is shown as ： stay mian() find MX_GPIO_Init(), And then right-click go to definition, You can find it .

 

  3、 ... and 、cubeMX Operate the buttons

1、 Hardware analysis of keys

 

  The mechanical key will shake during pressing , So there will be hardware anti jitter and software anti jitter , The hardware anti jitter is the capacitance in the figure above .

2、cubeMX Generate engineering framework

PA0 Select input mode , Because for hardware pull , So you don't have to choose up and down . When the default key is released ,IO Read as high level , When the key is pressed ,IO Read low .

PA1 Set as output , control LED The lamp .

3、keil Some control logic

stay main() Functional while In circulation , Write control logic , Time delay is set 8ms Software De chattering . Press the key to press LED Extinguish , Release to LED bright .

  while (1)
  {
    /* USER CODE END WHILE */

    /* USER CODE BEGIN 3 */
    if(HAL_GPIO_ReadPin(GPIOA,GPIO_PIN_0) == GPIO_PIN_RESET)
    {
        HAL_Delay(8);
        if(HAL_GPIO_ReadPin(GPIOA,GPIO_PIN_0) == GPIO_PIN_RESET)
        {
            HAL_GPIO_WritePin(GPIOA,GPIO_PIN_1,GPIO_PIN_SET);
        }
        else
        {
            HAL_GPIO_WritePin(GPIOA,GPIO_PIN_1,GPIO_PIN_RESET);
        }
    }
    }
  /* USER CODE END 3 */
}