TTL TO RS422 (B)

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Full-Duplex RS422
TTL TO RS485-2.jpg
Half-Duplex RS485
TTL TO RS485-1.jpg

RS485, TTL




TTL TO RS422 (B) is an industrial-grade rail-mounted electrically isolated TTL-to-RS485 serial converter.


  • Compatible with TTL/RS485 standard, converting the TTL signal into a balanced differential RS485 signal, supporting full-duplex communication.
  • Compatible with 3.3V ~ 5V TTL signal level, with anti-reverse connection and anti-over-voltage circuit on the power supply side.
  • Onboard unibody power supply isolation, provides stable isolated voltage and needs no extra power supply for the isolated terminal.
  • Onboard unibody digital isolation, allows signal isolation, high reliability, strong anti-interference, and low power consumption.
  • Onboard TVS (Transient Voltage Suppressor), effectively suppresses surge voltage and transient spike voltage in the circuit and is anti-electrostatic.
  • Onboard resettable fuse and protection diodes, ensure the current/voltage stable outputs, provide over-current/over-voltage protection, and improve shock resistance.
  • On-board RS485 input and output 120R resistors with built-in jumper caps for switching enable.
  • Industrial rail-mount ABS case design, small in size, easy to install, and cost-effective.


Model Galvanic isolated TTL to RS422 converter
Power Port Power Supply 3.3V ~ 5V
Interface Protection anti-over-discharge, reverse-proof
Device Interface Compatible with TTL / RS485 standard
TTL Interface Interface Type Screw terminal
Transmission Distance less than 10m
Transmission Model Point to point
RS422 Interface Interface type Screw terminal
Interface Protection Provide 600W lightningproof, surge-suppress and 15KV ESD protection
Terminal Resistance 120R, enabled/disabled via jumper (inside the case)
Transmission Distance About 1200m
Transmission Mode Point-to-multipoint
(Up to 32 nodes can be connected, and relays are recommended for more than 16 nodes)
Product Appearance Case Rail-mount ABS case, suitable for 35mm DIN rail
Dimensions 91.6 × 58.7 × 23.3mm

Basic Function

Convert TTL signal to balanced differential RS422 signal, which can be used for interface conversion, and node expansion, and can also be used to extend the communication distance.
TTL TO RS42209.jpg

Interface Introduction

TTL TO RS422020.jpg
TTL TO RS422021.png

* Note: the TTL TO RS422 (B) is designed to be used with RS422 devices, however, it is also possible to be used with RS485 devices (yet only sending is available). It is recommended to use TTL TO RS485 (B).

Communication Connection Diagram

TTL convert to RS422, point to point, full duplex communication, suitable for interface conversion

TTL TO RS422 030.jpg

TTL convert to RS422, point-to-multipoint, full duplex communication, suitable for expanding nodes

TTL TO RS422 031.jpg

Two groups TTL to RS422 conversion, point-to-point, full duplex communication, suitable for extending the communication distance of TTL

TTL TO RS422 032.jpg


TTL TO RS422 (B)010.jpg

Hardware Test

Test Note

Test Environment: PC (Windows).
Accessories required for testing:

  • TTL TO RS422 (B) --this product
  • USB TO TTL - not included
  • USB TO RS485/RS422 - not included

Test Hardware Connection

Connect the RS422 interface of TTL TO RS422 (B) to the PC with the USB to RS422 conversion cable. Connect the TTL interface of TTL TO RS422 (B) to the TTL interface of USB TO TTL, and then connect the USB port of USB TO TTL to the same PC for the self-transmission tests. The schematic diagram of the hardware connection is as follows:
TTL TO RS422 (B) 090.png

Note: The RS422 interface of this product also has two built-in 120R enabling resistors, which are enabled by default. Users can remove the case to modify the settings according to their needs. If signal isolation is required, GND can also be connected to the ground wire.

On the PC, open two SSCOM serial port debugging assistants, open the corresponding port number, set the same baud rate, and click Send at regular intervals to send and receive normally. The screenshot of the software test is as follows:
RS232 TO RS485 (B) Spec07.jpg





We have tested 921600bps and it can work stably.
The hardware itself has no special limitations to the use of rate but mainly depends on the access to the TTL and RS422 devices, as well as the communication environment and communication distance.


  • The module only provides a physical layer pure hardware level converter, without the need to configure parameters such as baud rate and nodes. Modbus communication requires implementation at the protocol layer.
  • It supports the connection of Modbus devices (Modbus sensors, instruments, etc.). Understanding the Modbus protocol involves knowledge of Modbus function codes and data formats. Modbus has multiple function codes, with each code corresponding to a specific operation, such as reading coil status, reading input status, reading holding registers, etc.


  • In general, the short-distance communication can be removed from RS422/RS485's two 120Ω terminal, and connect jumper caps to NC.

USB TO RS232 faq.png

  • When multiple devices connect to the RS485 serial bus over a long distance, in general, we add 120Ω matching resistors to the first and last devices on the RS485 bus.

RS485 TO WIFI-ETH-02.png



Technical Support

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