How to set a pin to high impedance

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How to set a pin to high impedance [Copy link]

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There are several issues regarding high impedance state:

1. Does high impedance state refer to input or output?

2. Are the ways to set the pins of STM32 and 8051 to high-impedance state the same? What are the specific setting methods?

Thank you all

maychang

『1. Does high impedance state refer to input or output?』

The high impedance state must refer to the input and cannot refer to the output.

maychang

『2. How to set the pins of STM32 and 8051 to high impedance in the same way?』

The 8051 does not have a high-impedance state, and there is no way to set it.

vincentc543

The reference ST data is set as follows

#define GPIO_MODE_INPUT MODE_INPUT /*!< Input Floating Mode
void FLOATING_GPIO_Config(void)
{
GPIO_InitTypeDef GPIO_InitStruct = {0};
GPIO_InitStruct.Pin = GPIO_INPUT_Pin;
GPIO_InitStruct.Mode = GPIO_MODE_INPUT; //<=Floating
GPIO_InitStruct .Pull = GPIO_NOPULL; // < = Set No pull up and down
HAL_GPIO_Init(GPIOG, &GPIO_InitStruct);
}

RichSJ

ST32 input can usually be set to digital or analog. Only when it is set to digital can it be set to high impedance. It can also be set to TTL or CMOS. As far as I understand it, CMOS is high impedance.

The output can be set to high impedance. The output setting is relatively complicated. Different sequences have different methods. It is set using internal registers.

In the previous article, the table on page 7 gives an introduction.

vincentc543

As Master Maychang said, high impedance cannot be output.

The electrical concept of high impedance output is that the circuit is broken, and the output control backend cannot be controlled if the circuit is broken.

ST GPIO output only has Open Drain and Push Pull modes

RichSJ

There is at least one Tri mode (three-state), which is high impedance. It is used for low-power applications to save chip power consumption.

You can take a look at the copy form I gave you last time.

RichSJ

Of course, you are right. In the normal "working" state, it is impossible to break the circuit. It is just because of the low power consumption requirement that the Xitong has to enter a non-working state (sleep)

RichSJ

To add, the three-state design should appear before the low power consumption requirement. Sometimes when several driving sources are used to drive the same target, the others should be set to three-state and only one should be left "working".

chunyang

Read the device manual carefully. If you read it carefully, you won't have to ask those two questions.

bigbat

"High impedance state" is one of the states of the three-state gate in the digital circuit, that is, "off". After being set to "high impedance state", the states of the two ends are not affected by each other with the three-state gate as the boundary. Don't ask this kind of question in the future. If you want to enter the industry, start learning from analog electronics and digital electronics. The current industry is seriously involuted and you can't accomplish anything without being down-to-earth.