A Swedish developer has released the Industrial RS485 / Modbus HAT, a compact add-on board that brings industrial serial communication to any 40-pin Raspberry Pi. The HAT features an onboard RS-485 transceiver with TVS diode protection for ESD and voltage spike resistance, communicates via the Pi's hardware UART interface, and includes Tx/Rx diagnostic LEDs. It connects through 5-pin screw terminals carrying RS-485 A, B, and GND signals, using an off-the-shelf RS-485 to TTL module.
The board accepts 7V to 32V DC input through screw terminals, making it compatible with standard 12V and 24V industrial power rails. An integrated DC-DC buck converter provides 5V output to power both the Raspberry Pi and the RS-485 transceiver, eliminating the need for a separate USB power supply in control cabinets. The HAT works with all 40-pin Raspberry Pi models including Pi 3, Pi 4, Pi 5, and Pi Zero.
EngineElectronicAccessories designed the board specifically for OpenPLC, an open-source programmable logic controller suite, with pinout and timing optimized for low-latency ladder-logic execution. The HAT suits energy monitoring projects like reading SDM smart meters or interfacing with solar and battery systems using the Modbus protocol. The project is partially open source with PDF schematics and documentation available on GitHub. Note that the RS-485 interface lacks galvanic isolation, typical for this price range.
The Industrial RS485 / Modbus HAT costs $9 (€8) and ships from Sweden with $7 to $15 (€6 to €14) shipping depending on destination. Alternative RS-485 HATs for Raspberry Pi are also available from other manufacturers.
