{Embedded stm32} on gpio Input and Output

The open and drain outputs do not output voltage. Low Power Supplies are grounded at ordinary times, while high power supplies are not grounded at ordinary times. If the external pull-up resistor is used, the output voltage is usually pulled to the power supply voltage of the pull-up resistor.

This method is suitable when the peripheral voltage of the connection is lower than that of the single chip microcomputer.

Open-drain output: the output end is equivalent to the collector of the transistor. To obtain a high-level state, the output end must be able to pull up the resistor. It is suitable for current-type drive and has a strong ability to absorb the current (generally less than 20 mA ).

The push-pull output means that the single-chip microcomputer pin can directly output the High-level voltage. Low-Power grounding at ordinary times, high-power output of single-chip microcomputer power supply voltage at ordinary times. In this way, do not connect the pulling resistance. However, if the output end may be grounded, the output high level may cause instability of the single chip microcomputer, or even burn out the pins.

> Push-pull output: outputs high and low levels and connects to digital devices.

When I/O configuration is input, there are also analog inputs in addition to the three modes you mentioned.
Up-pull input mode: the difference is that when there is no input signal, the default input is high (because of weak up-pull ).
Drop-down input mode: the difference is that when there is no input signal, the default input is low (because there is a weak drop-down ).
As the name suggests, the float input mode ensures that the input signal is clear.

The following is a reprint ........Http://bbs.ednchina.com/BLOG_ARTICLE_159008.HTM

Differences between the push-pull output and the open/Open output:

> Push-pull output: outputs high and low levels and connects to digital devices.

> Open-drain output: the output end is equivalent to the collector of the transistor. to obtain the High-level status, you need to pull up the resistance. it is suitable for current-type drive, and its ability to absorb current is relatively strong (generally less than 20 mA ).

//////////////////////////////////////// //////////////////////////////////////// //////////////////////////////////////// ////////////////// What are the characteristics of the open/drain output of the transistor, is it the same as pushing and pulling,

Problem:

Many chips have different power supply voltages, including 3.3v and 5.0 v. It is necessary to connect different ports of several kinds of IC together. Is it possible to connect them directly? In fact, the system is applied to I2C.

Answer:

1. Some 3.3v devices have 5 V compatibility and can be directly connected using this compatibility.

2. Apply a voltage converter. For example, tps76733 is a 5 V input, which is converted to 3.3 V and 1A output.

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Characteristics and Application of Open leakage Channels

In circuit design, we often encounter the concepts of open drain and open collector. The "drain" mentioned in the so-called open-leakage circuit concept refers to the drain pole of the MOs. Similarly, the "set" in the open set circuit refers to the collector of the transistor. An on-line leakage circuit refers to a circuit with extremely high output of the MOs. In general, the pull-up resistance is added to the circuit with an external leakage pole. The complete open-leakage circuit should be composed of an Open-leakage device and an open-leakage pull-up resistor. 1:

Circuit components have the following characteristics:

1. Use the drive capability of the external circuit to reduce the internal drive of the IC. When the internal MOS of the IC are turned on, the driving current is from the external VCC flowing through the R pull-up, the MOs to Gnd. The IC only needs a very low gate drive current. 1.

2. You can connect multiple pin pairs with open/missing output to an online line. Form a "logical" relationship. 1. When any one of pin_a, pin_ B, and pin_c gets low, the logic for online exposure is 0. This is also the principle that I2C, SMBus, and other bus determine the bus occupation status.

3. You can change the transmission level by changing the voltage of the pull-up power supply. 2. The logic level of the IC is determined by the power supply vcc1. the output height is determined by vcc2. In this way, we can use the low-level logic to control the output high-level logic.

4. when the Open-drain pin is not connected to the external pull-up resistor, it can only output a low level (therefore, for the P0 port of the classic 51 single-chip microcomputer, an external pull-up resistor is required for the input/output function, otherwise, the High-Level Logic cannot be output ).

5. The standard opening and dropping feet generally only have the output capability. Only by adding other judgment circuits can two-way input and output capabilities be achieved.

Note:

1. The principle of open-circuit and open-circuit is similar. In many applications, we use open-circuit to replace open-circuit. For example, an input pin must be driven by an open-leakage circuit. The common driving method is to use a transistor to form an open circuit to drive it, which is convenient and cost-effective. 3.

2. The R pull-up resistance determines the speed of the logical level conversion. The higher the resistance, the lower the speed and power consumption. And vice versa.

The push-pull output is generally called the push-pull output. It should be more suitable than the CMOS output in the CMOS circuit. The push-pull output capability in the CMOS circuit cannot be as large as the bipolar output capability. The output capability depends on the area of the N-tube p-tube output in the IC. Compared with the open-drain output, the level of push-pull is determined by the IC power supply, and logical operations cannot be performed simply. Push-pull is the most widely used output-level design method in the Current CMOS circuit.

Note the following when simulating the I2C interface at at91rm9200 gpio !!

1. What is OC and OD?

Open collector gate (open collector oC or open source OD)

Open-drain refers to the open-collector output, that is, the open-collector output in TTL. It is generally used for wire or, wire and some are also used for current driving.

Open-drain is for MOS tubes, and open-collector is for bipolar tubes, there is no difference in usage.

Open-drain circuit has the following features:

1. Use the drive capability of the external circuit to reduce the internal drive of the IC. Or drive load higher than the chip power supply voltage.

2. You can connect multiple pin pairs with open/missing output to an online line. A logical relationship is formed by means of an up-pull resistor without adding any device. This is also the principle that I2C, SMBus, and other bus determine the bus occupation status. If it is used as a totem output, it must be connected to the pulling resistance. When the capacitive load is connected, the descent delay is the transistor in the chip, which is the active drive and the speed is fast. The Descent delay is the passive external resistance, and the speed is slow. If the speed and high resistance are required, the power consumption will be high. Therefore, the choice of load resistance should take into account both power consumption and speed.

3. You can change the transmission level by changing the voltage of the pull-up power supply. For example, the TTL/CMOS level output can be provided by adding a pull-up resistor.

4. If the Open-drain pin is not connected to the external pull-up resistor, only the low level can be output. In general, open-drain is used to connect devices of different levels.

5. The normal CMOS output level is the upper and lower two tubes. Remove the above pipes as open-drain. This output has two main purposes: level conversion and line and.

6. Due to the open circuit of the lower-level circuit, the latter-level circuit must be connected to the upper-level resistance, and the power supply voltage of the upper-level resistance can determine the output level. In this way, you can convert any level.

7. the cables and functions are mainly used when multiple circuits are used to pull down the same signal. If the current circuit does not want to pull down, It outputs a high level because the pipe above open-drain is removed, high level is achieved by external pull-up resistance. (For a normal CMOS output level, if one output is high or the other is low, it is equal to a short circuit of the power supply .)

8. Open-drain provides a flexible output mode, but it also has its weakness, that is, the delay of the rising edge. Because the rising edge is charged by the external pull passive resistance, the latency is small when the resistance is selected, but the power consumption is large; otherwise, the delay is large and the power consumption is small. Therefore, if you have requirements for latency, we recommend that you use the descent edge output.

2. What is line or logic and line and logic?

On a single node (line), connect an upstream resistor to the Collector C or drain D of the power supply VCC or VDD and N or NMOS transistors, the emission pole E or source Pole s of these transistors are connected to the ground line. As long as there is a transistor saturated, this node (line) is pulled to the ground wire.

Because the base pole of these transistors is injected with current () or the gate is added with a high level (NMOS), the transistor will be saturated, so these base poles or gate nodes (lines) or non-Nor Logic. if this node is followed by an inverter, It is the or logic.

Note: For personal understanding, the cables and cables are connected to the power supply. (~ A )&(~ B) = ~ (A + B) the concept of this concept is easily understood by the formula;

If the drop-down resistor and PNP or PMOS tubes are used, they can form non-NAND logic, or convert and/or logic using a negative logical relationship.

Note: wire or drop-down resistor to the ground. (~ A) + (~ B) = ~ (AB );

These transistors are often open collector oC or source open circuit OD output of some logical circuits. this logic is usually called line and/line or logic. When you see that some chip's oC or OD output end are connected together and there is a pull-up resistor, this is the line or/line, but sometimes the pull-up resistance is done in the input of the chip.

By the way, it is suggested that the output end of the OC or OD chip cannot be connected together. The two-way output end of the bus can be managed together, and only one output can be made at the same time, other high-impedance states can only be input.

3. What is a push-pull structure?

Generally, two transistors are controlled by two complementary signals, which always end when one transistor is turned on. the OC (open collector) door circuit must be used to achieve the line and the need. if there are two transistors in the output level, they are always in one conduction and one cutoff state, that is, two three-level tubes are pushed and connected. Such a circuit structure is called a push-pull circuit or a totem-pole) output Circuit (unfortunately, the figure cannot be attached ). When the output power is low, that is, when the lower-level load gate inputs low, the output current is when the lower-level load gate inputs T4; when the output power is high, that is, when the lower-level load gate inputs High, the current at the output end will be pulled from the lower-level power supply through T3 and D1. In this way, the output level is usually, T3
One way and four way will work alternately, thus reducing power consumption and improving the affordability of each tube. Regardless of the path, the on-resistance of the pipe is very small, so that the RC constant is very small, and the transformation speed is very fast. Therefore, the push-pull output level not only improves the load capacity of the circuit, but also increases the switching speed. For your reference.

The push-pull circuit is a three-circuit transistor or transistor with the same parameters. It exists in the circuit in the push-pull mode. It is responsible for waveform amplification tasks of plus or minus half weeks. When the circuit works, the two symmetric power switches have only one on-going switch at a time, so the low conduction loss is highly efficient.

The output can either inject current to the load or extract current from the load.

That's all.