What is the difference between RS232, RS485 and TTL

By sdga:NiceRF Wireless Technology Co., Ltd

In the Internet of Things industry, as long as you are an embedded engineer, you will generally be exposed to the concepts of RS232, RS485, and TTL. Do you come across this concept and search on Google? Here are the differences between RS232 and RS485 and TTL interfaces.


Electrical characteristics of RS232 interface

In RS-232-C, the voltage of any signal line is a negative logic relationship. That is: logic "1" is -3 to -15V; logic "0" is +3 to +15V.

RS-232-C interface connector generally uses the DB-9 plug socket, usually the plug is at the DCE end, and the socket is at the DTE end. The RS-232 port of the PC is a 9-pin socket. The RS-232 interface of some devices connected to the PC does not use the other party's transmission control signal, so only three interface lines are needed, namely "transmit data TXD", "receive data RXD" and "signal ground GND". RS-232 transmission line adopts shielded twisted pair.


The electrical characteristics of RS485

RS485 adopts differential signal negative logic. Logic "1" is represented by the voltage difference between the two wires as -(2~6)V; the logic "0" is represented by the voltage difference between the two wires as +(2~6)V. The interface signal level is lower than RS-232-C, it is not easy to damage the chip of the interface circuit, and the level is compatible with the TTL level, and it is convenient to connect with the TTL circuit. The highest data transmission rate of RS-485 is 10Mbps.


TTL level

TTL level signals are most used because usually data representation adopts binary regulations, +5V is equivalent to logic "1", 0V is equivalent to logic "0", which is called TTL (transistor-transistor logic level) signal System, which is a standard technology for communication between various parts of a device controlled by a computer processor.


The difference between RS232 and RS485, TTL

1. RS232, RS485, TTL refer to level standards (electrical signals)

2. TTL level standard Yes, low level is 0, high level is 1 (to ground, standard digital circuit logic).

3. The RS232 level standard is that the positive level is 0, and the negative level is 1 (to ground, both positive and negative 6-15V can be used, and even high-impedance state can be used).

4. RS485 is similar to RS232, but uses differential signal logic, which is more suitable for long-distance and high-speed transmission.

Level adapter board SU108


The above is the difference between RS232, RS485 and TTL. Our company has level conversion series module SU108, which can directly convert the level of different voltage interfaces into standard USB level. It can be easily connected to various series of digital transmission modules. Perform configuration and communication operations on the PC side. SU108 level adapter board address:

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