STM32 - GPIO input / output mode

GPIO I / O mode

Eight modes of input and output

Floating input	Open drain output
Pull up input	Push pull output
Drop down input	Push pull multiplexing
Analog input	Open drain multiplexing

1、 Pull up resistance ： Connect the uncertain signal to the high level through resistance, and initialize the electrical signal to the high level

2、 Pull down resistance ： Connect the uncertain signal to the low level through resistance, and initialize the electrical signal to the low level

Four input modes ：

Pull up input ：

By default, the input pin data is 1 High level

analog signal 3.3v 5v 1.9v

digital signal 0 1

Drop down input ：

The default input pin is 0

Low level

Floating input

That is, the pin is not connected to high level or low level , That is, the input pin is floating

The pin voltage is an uncertain value , Usually used for IIC,USART

Analog input ：

analog signal ： 3.3v 5v 1.9v

digital signal ： 0 1

Commonly used in AD transformation

Four output modes ：

Open drain output ：

Can output 0 and 1

It is suitable for occasions with mismatched levels

To get a high level, you need to pull up the resistor

Open drain multiplexed output ：

Internal and external functions ：

TX1,MOSI,MISO,SCK,SS

Push pull output ：

Can output high and low level 0 and 1

Applicable to two-way IO Use

Push pull multiplex output

GPIO The configuration when the port is used as the second function

Of on-chip and off-chip functions IIC Of SCL,SDL