Modbus M2M Controller C4

RS422/RS485Internet of ThingsTCP/IP

Overview
Industrial IoT controller based on the Raspberry Pi Compute Module 4. Available in housings for DIN-rail and wall mounting in sizes 4MU, 8MU and 12MU. Fits standard switchboard cabinets with 45 mm front panel cutout. Wide-range power supply (12–48 Vdc). ARM co-processor for time-critical IO handling, persistent memory, RTC and diagnostics.

What's different?
Includes an industrial housing and an ARM co-processor providing a unique 96-bit serial number, 2 kB ferromagnetic RAM for persistent values, real-time clock with backup capacitor, status LEDs and a DIP switch for software use. Standard Compute Module 4 interfaces (Micro HDMI, Ethernet, USB 2.0) and selectable RAM/SD options are retained.

Compute Module 4 features (available on the controller)

• 1× Micro HDMI
• 1× Ethernet
• 2× USB 2.0
• RAM options: 2 GB, 4 GB, 8 GB
• 32 GB SD‑Card with Linux OS (preinstalled)

Built-in inputs & outputs and IO handling
The ARM co-processor handles IO internally; host software accesses IO via mapped serial interfaces. Available IO variants include digital inputs/outputs, relay outputs and special IOs for LED strips, temperature sensors and blind/shade control. Universal analog I/O expansion (AIOX) offered in 4/8/16 channels; each channel configurable individually.

Analog / digital IO modes (AIOX channel configurations)

• Analog input: 0/2–10 V or 0/4–20 mA
• Analog output: 0/2–10 V or 0/4–20 mA
• Resistor measurement input: 0 to 1 MΩ
• Sensor input: PT100, PT1000, NI1000‑DIN43760
• Digital input: 24 Vdc or dry contact

Digital outputs (C4-only DOs versions)
Versions with integrated digital outputs: up to 30 Vdc and up to 750 mA per channel. Outputs protected against short circuit and thermal overload. Per-channel diagnostics available for remote monitoring.

Serial interfaces and protocols
Serial interfaces are exposed by the ARM co-processor for IO and RS485 communication. Use /dev/ttyACM0 for a simple ASCII text protocol, /dev/ttyACM1 for MODBUS/RTU master. RS485 is mapped via USB (e.g. /dev/ttyACM2) with hardware direction switching handled by the co-processor.

Software and connectivity
Delivered with standard Raspberry Pi Linux distribution. Supports common open-source stacks and tools: Node-RED, Node.js, Python, Java, C/C++, databases (MariaDB, MongoDB, InfluxDB, PostgreSQL), visualization (Grafana, Apache), home automation (OpenHAB, FHEM, Home Assistant, ioBroker), cloud protocols (MQTT, HTTPS, Azure IoT, AWS), VPN/router solutions (OpenWrt, OpenRouter, OpenVPN, WireGuard), multimedia (KODI) and industrial PLC (CODESYS). Also suitable for custom software development.

Versions and selectable options

• Digital output counts: 6×DO, 12×DO, 24×DO, 30×DO, 60×DO, 90×DO
• C4 add-on options: none, 2nd Ethernet, LTE modem
• C4 RAM sizes: 2 GB, 4 GB, 8 GB

Documents and attachments (available for product variants)
Catalog pages, product attachments, MODBUS mapping & ASCII command lists, product manual and declaration of conformity are available as downloadable PDFs for the C4 variants.

Reference / Ordering
Example product reference for a selected variant: RESI-C4-A-6DO-2GB.

Technical specifications

• Product family: C4 (Compute Module 4 based IoT controller)
• Mounting: DIN-rail and wall mounting; fits 45 mm front panel cutout
• Housing sizes: 4MU, 8MU, 12MU
• Power supply: 12–48 Vdc wide-range
• ARM co-processor: unique 96-bit serial number, 2 kB ferromagnetic RAM, RTC with backup capacitor, status LEDs, DIP switch
• Compute Module 4 interfaces: Micro HDMI, Ethernet, 2× USB 2.0; RAM options 2/4/8 GB; 32 GB SD-card with Linux
• Digital outputs: up to 30 Vdc, up to 750 mA per channel, short-circuit and thermal overload protected, per-channel diagnostics
• Analog IO (AIOX): 4/8/16 channels, configurable per channel (0/2–10 V, 0/4–20 mA, resistor 0–1 MΩ, PT100/PT1000/NI1000)
• Digital inputs: 24 Vdc or dry contact
• Serial interfaces: /dev/ttyACM0 (ASCII), /dev/ttyACM1 (MODBUS/RTU master), RS485 mapped via USB (/dev/ttyACM2) with hardware direction switching by co-processor
• Optional add-ons: 2nd Ethernet, integrated LTE modem
• Typical ordering example: RESI-C4-A-6DO-2GB