The RS422 to TTL Bidirectional Signal Module is a compact, full-duplex protocol converter designed to bridge RS422 differential signals with TTL-level UART signals from microcontrollers. Built around the MAX490 transceiver chip, this module enables reliable, long-distance serial communication between microcontrollers (Arduino, ESP32, STM32, etc.) and industrial RS422 devices, sensors, and equipment.
At the heart of the module is the MAX490, a low-power, full-duplex RS422 transceiver from Maxim Integrated (now Analog Devices). The MAX490 features one driver and one receiver, supporting full-duplex communication — meaning data can be transmitted and received simultaneously. This is a key advantage over half-duplex RS485, making the module ideal for applications requiring simultaneous bidirectional data flow.
The module performs bidirectional signal conversion:
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TTL to RS422 — Converts 3.3V/5V TTL UART signals from your microcontroller to differential RS422 signals for long-distance transmission.
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RS422 to TTL — Converts incoming differential RS422 signals back to TTL levels for your microcontroller to read.
The MAX490 supports data rates up to 2.5 Mbps, making it suitable for high-speed serial communication. The RS422 differential signaling provides excellent common-mode noise rejection and allows cable runs of up to 1200 meters (at lower data rates), far exceeding the range of standard TTL or RS232 interfaces.
The module includes screw terminals for secure connection of the RS422 A, B, Y, and Z differential lines, and pin headers for easy connection to your microcontroller’s UART pins (TX, RX, VCC, GND). LED indicators provide visual feedback for power and data activity, making it easy to verify operation during setup and troubleshooting.
The board operates from a 3.3V or 5V supply, making it compatible with both modern low-power microcontrollers and traditional 5V systems. The compact PCB design with mounting holes allows easy integration into control panels, DIN rails, and equipment enclosures.
The module is widely used in industrial automation, long-distance serial communication, motor control, PLC interfacing, data acquisition systems, security systems, and any application where reliable, noise-immune serial communication is required over extended distances.
Important Note: The RS422 standard uses four wires (TX+, TX-, RX+, RX-) for full-duplex communication. Ensure proper termination (typically 120Ω) at the far end of long cable runs to minimize signal reflections. Use twisted-pair cable for best noise immunity. The module is not compatible with RS485 without additional wiring configuration, as RS485 is typically half-duplex.
Whether you are connecting a microcontroller to an industrial RS422 device, extending serial communication over long distances, or building a noise-immune data link, the RS422 to TTL Bidirectional Signal Module provides a reliable, well-supported solution. It is suitable for individual engineers, students, and businesses purchasing in bulk for product development or industrial applications.
Features
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MAX490 transceiver — Reliable, industry-standard RS422 full-duplex chip
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Full-duplex communication — Simultaneous transmit and receive
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Bidirectional conversion — TTL to RS422 and RS422 to TTL
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High data rate — Up to 2.5 Mbps
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Long-distance support — Cable runs up to 1200 meters (at lower data rates)
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Excellent noise immunity — Differential signaling rejects common-mode noise
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3.3V/5V compatible — Works with both modern and traditional microcontrollers
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Screw terminals — Secure RS422 A/B/Y/Z connections
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Pin headers — Easy UART connection to microcontroller
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LED indicators — Power and data activity feedback
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Compact PCB design — With mounting holes for easy installation
Technical Specifications
| # | Parameter | Specification |
|---|---|---|
| 1 | Transceiver Chip | MAX490 |
| 2 | Interface Type | RS422 to TTL (full-duplex) |
| 3 | Data Rate | Up to 2.5 Mbps |
| 4 | Supply Voltage | 3.3V or 5V DC |
| 5 | RS422 Connections | A, B, Y, Z (screw terminals) |
| 6 | TTL Connections | TX, RX, VCC, GND (pin headers) |
| 7 | Cable Length | Up to 1200m at lower data rates |
| 8 | Module Dimensions | Compact PCB with mounting holes |
