R4PIN08: An Ultra-Compact 8-Channel RS485 Modbus RTU Digital I/O Module for Embedded Systems

Looking for a compact, low-power digital I/O expansion module for your PLC, MCU or industrial automation project?

The Eletechsup R4PIN08 combines 8 configurable digital I/O channels, RS485 communication and Modbus RTU in an ultra-small PCB measuring just 30 × 25.4 × 2 mm and weighing approximately 3 grams.

It is designed for engineers who need flexible digital input/output expansion without the size and cost of a conventional PLC I/O module.

⚙️ Key Technical Specifications

✅ 8 configurable digital I/O channels

Select five operating configurations using jumpers:

• 8DI — 8 digital inputs

• 8DO — 8 digital outputs

• 4DI + 4DO

• 2DI + 6DO

• 6DI + 2DO

✅ RS485 + Modbus RTU communication

Supported Modbus function codes include read 01/02/03 and write 05/06/15/16.

✅ Flexible NPN/PNP configuration

Switch input and output logic configurations through registers 0x00F5 and 0x00F6, according to the selected hardware version and supported configuration.

✅ TTL-level digital I/O

• Input: 3.3V / 5V TTL

• Output: 5V TTL

• Selectable high-level or low-level logic

Important: These are logic-level I/O signals, not isolated industrial 24V inputs or high-current relay outputs. Check the interface requirements before connecting industrial field devices.

✅ Low power consumption

• Main supply: DC 6–25V, reverse-polarity protected

• Additional supply: DC 4–5V, polarity must be observed

• Operating current: approximately 7–13mA

✅ Configurable serial communication

Baud rates from 1200 to 115200 bps, with none, odd or even parity.

✅ Multi-device RS485 networks

Supports up to 247 device addresses in Modbus command mode, subject to network design and configuration.

📐 Ultra-Compact Design

At only 30 × 25.4 × 2 mm, the R4PIN08 is ideal for embedded control systems, custom PCB integration, breadboard prototyping and space-constrained OEM equipment.

🔧 Potential Applications

• PLC and HMI digital I/O expansion
• Embedded controller and MCU projects
• RS485 remote digital input monitoring
• Low-power industrial control systems
• Custom automation equipment
• ESPHome-based integration experiments
• OEM electronics and compact control boards
• Digital signal collection and TTL-level output control

💡 Real-World Integration Discussion

In August 2024, a user on the KinCony community forum asked about connecting the R4PIN08 to a KC868-A16 controller and using ESPHome YAML to handle its digital inputs.

The discussion illustrates a practical integration challenge: third-party controllers may require custom Modbus RTU configuration rather than native plug-and-play support.

Read the discussion:
https://www.kincony.com/forum/showthread.php?tid=6076

This is an independent compatibility discussion, not a claim of official KinCony certification or a confirmed successful deployment.

🚀 Why Choose Eletechsup R4PIN08?

✔ Eight configurable digital I/O channels
✔ Five selectable I/O configurations
✔ NPN/PNP logic configuration
✔ Standard RS485 Modbus RTU communication
✔ Very small footprint and lightweight design
✔ Low operating current
✔ Flexible integration into custom embedded systems

Whether you are developing a compact remote I/O system, an embedded automation controller or a custom digital signal acquisition board, the R4PIN08 offers a flexible foundation for your next project.

🔗 Official product page:
https://eletechsup.com/products/r4pin08-dc-5v-12v-24v-8ch-rs485-2-54mm-pin-core-board-modbus-rtu-input-and-output-control-plc-hmi-remote-io-expanding-board-r4pin08

📣 Engineers and developers: Would you use the R4PIN08 for PLC expansion, MCU integration or an ESPHome-based automation project? Share your application requirements with us!

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