Difference between RS232 and RS485

RS232 and RS485 are standards for data cables. To exchange data between nodes in a network, the most commonly used tools are line controllers and receivers.


The RS-232 serial port, present in all current computers, is the most commonly used way to perform data transmissions between computers.

The RS-232 consists of a 25-pin type DB-25 connector, although it is normal to find the 9-pin DB-9 version, cheaper and even more extended for certain types of peripherals

The signals with which this serial port works are digital, + 12V (logical 0) and -12V (logical 1), for the input and output of data, and vice versa in the control signals.


It is defined as a system in differential multipoint transmission bus, it is ideal to transmit at high speeds over long distances (35 Mbps up to 10 meters and 100 Kbps in 1,200 meters) and through noisy channels, since it reduces the noises that appear in the voltages produced in the transmission line.

The physical medium of transmission is an interlaced pair that supports up to 32 stations in 1 single wire, with a maximum length of 1,200 meters operating between 300 and 19,200 bps and half-duplex communication (semi-duplex).

The differential transmission allows multiple drivers giving the possibility of a multipoint configuration. Being a fairly open standard allows many and very different configurations and uses.

Difference between RS232 and RS485:

The data transfer is generally classified as single-ended and differential, RS232. RS232 allows data transfer at relatively slow speeds (up to 20K bits / sec) and short distances (up to 50 feet).

When the data transfer has to be done over long distances, and also at a higher speed, the single-termination methods are ineffective. This is when the transmission of differential data enters the scene, as it provides superior performance.

These signals cancel out the negative effects of the earth changes and induced noise signals in a network. RS422 was produced to meet these requirements, but over time it has been found that RS422 can not be used to build a true multipoint network.

Enter RS485, which meets all the requirements of a truly multipoint network. RS485 specifies up to 32 controllers and 32 receivers on a single bus. The RS485 controllers are also capable of handling the problem of data collision and bus failure conditions.


  1. RS232 is a point to point communication and RS485 is multidrop communication
  2. In RS232 you cannot connect more than two device, while RS485 allows to connect up to I think max 128 device.


The voltage level of RS232 is
-3 to -25 for 1
+3 to +25V for 0

while RS485 is based on differential voltage (0-5v) difference is 240mV for 1 and -240mV for 0.


  • RS232 – 100 meters
  • RS485 – 1km


Noise immunity is high for RS485 as it is balanced protocol and differential protocol.


Pin for 232 is (Rx Tx and GND) while in case of RS485 it is (A(+) and B(-)) no need to transmit GND signal


Instrumentation Engineer

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