Can RS-232 be charged?

1, Electrical characteristics of RS-232
Firstly, we need to clarify the electrical characteristics of the RS-232 interface. The RS-232 interface adopts negative logic level, that is, the level of logic "1" is between -3V and -15V, and the level of logic "0" is between+3V and+15V. This high-level characteristic gives the RS-232 interface a certain amount of energy during signal transmission, but the term 'charged' here does not refer to the interface itself being able to actively provide power, but rather to the electrical signal energy that the interface possesses during signal transmission.
2, Power supply mode of RS-232
There are actually two interpretations regarding the power supply method of the RS-232 interface. One refers to the electrical signal energy transmitted through the signal line during the communication process of the RS-232 interface; Another type refers to providing power to external devices through the RS-232 interface.
The energy of electrical signals transmitted through signal lines: As mentioned earlier, the RS-232 interface has a certain amount of energy in the communication process, but this energy is mainly used for data transmission and reception, rather than directly providing power to external devices.
Providing power to external devices through the RS-232 interface: Although the RS-232 interface itself is not directly designed as a power output port, in certain specific situations, the voltage provided by certain signal lines in the RS-232 interface (such as DTR, RTS, etc.) during device initialization or specific states can be used to provide limited power support for external devices. However, this power supply method is usually only suitable for low-power devices and has issues with current limitation and voltage instability.
3, Live Application of RS-232
In practical applications, the "live" characteristics of the RS-232 interface are mainly reflected in the following aspects:
Signal transmission: The RS-232 interface transmits electrical signal energy through signal lines, enabling data exchange between computers and external devices. This data exchange process itself is' charged 'because electrical signals require energy consumption during transmission.
Auxiliary power supply: In certain specific situations, as mentioned earlier, certain signal lines in the RS-232 interface can be used to provide auxiliary power to low-power devices. Although this power supply method is limited, it still has certain practical value in certain application scenarios.
Extended applications: In addition to basic communication functions, the RS-232 interface can also achieve more functions through some extended circuits or devices. For example, through devices such as RS-232/RS-485 converters, the RS-232 interface can be extended to a communication interface with longer distances and higher speeds; Through specific power conversion circuits, power can also be extracted from the RS-232 interface to supply power to other devices.
4, Precautions and Limitations
Although the RS-232 interface can be used for "live" applications in some cases, the following points should be noted:
Current limitation: The RS-232 interface provides limited current and can usually only meet the needs of low-power devices. When attempting to extract power from the RS-232 interface, it is necessary to ensure that the current limit of the interface is not exceeded to avoid damaging the interface or external devices.
Voltage instability: Due to the possible changes in voltage of the RS-232 interface during communication (such as the voltage of the DTR and RTS signal lines may differ before and after device initialization), there may be voltage instability issues with the power extracted from the RS-232 interface. When designing circuits, it is necessary to consider this and take appropriate measures to stabilize the voltage.
Transmission distance and speed limitations: The RS-232 interface has limited transmission distance and speed, and is typically suitable for short distance, low rate communication scenarios. When long-distance and high-speed communication is required, other more advanced interface standards should be considered.