Internet of Things M2M Controller C4-A

cellular IoTModbusTCP/IP

USE THE PERFORMANCE OF THE RASPBERRY PI® COMPUTE MODULE 4 IN YOUR SOLUTIONS

General
RESI developed an industrial-grade IoT controller based on the Raspberry Pi® Compute Module 4. The device is housed in an industrial enclosure for DIN-rail and wall mounting; available enclosure sizes: 4MU, 8MU and 12MU. Suitable for standard control cabinets with a 45 mm front cut-out. Integrated wide-range power supply 12–48 VDC.

Extended hardware (ARM® coprocessor)
An ARM® coprocessor handles time-critical tasks (e.g. RS485) and provides additional functions: unique 96-bit serial number, integrated 2 kB ferromagnetic RAM for persistent values, real-time clock with backup capacitor, status LEDs and DIP switches for software use.

Standard features of the Compute Module 4
1x Micro HDMI, 1x Ethernet, 2x USB 2.0. Available RAM options: 2 / 4 / 8 GB. 32 GB SD card with preinstalled Linux OS available.

BUILT-IN INPUTS AND OUTPUTS
Several versions with integrated I/Os are available. The ARM® coprocessor processes the I/Os internally so the application software only needs to use a serial interface:

• dev/ttyACM0: communication using a simple ASCII text protocol
• dev/ttyACM1: communication using a MODBUS/RTU master protocol
• RS485 is mapped by the coprocessor via USB to /dev/ttyACM2; RS485 direction switching is handled in hardware by the coprocessor.

Available IO types: digital inputs and outputs, versions with relay outputs, special IOs (e.g. LED strip drivers, temperature sensor inputs, shutter control).

Universal analog I/O (AIOX)
Available with 4 / 8 / 16 channels. Each channel is individually configurable as:

• Analog input: 0 / 2–10 V or 0 / 4–20 mA
• Analog output: 0 / 2–10 V or 0 / 4–20 mA
• Resistance measurement input: 0 to 1 MΩ
• PT100, PT1000, NI1000-DIN43760 sensor input
• Digital input for 24 V DC or dry contact

HOW TO USE THE SERIAL INTERFACE?
The ARM® coprocessor maps the RS485 interface over USB to a serial device /dev/ttyACM2. This appears as a native serial interface in Linux software; the time-critical direction switching for RS485 is performed by the coprocessor, not the Linux OS.

WHAT SOFTWARE?
The controllers are supplied with the standard Raspberry Pi Linux distribution. Supported software/frameworks (selection):

• Node-RED, NodeJs, Python, Java, JavaScript, HTML, C#, C++, Scratch
• Databases: MariaDB, MongoDB, InfluxDB, PostgreSQL
• Visualization/servers: Grafana, Apache
• Home automation: OpenHAB, FHEM, Home Assistant, ioBroker
• Cloud/communication: MQTT, HTTPS, Azure IoT, AWS web services
• VPN/router solutions: OpenWrt, OpenRouter, OpenVPN, WireGuard
• Multimedia: KODI
• PLC solutions: CODESYS

VARIANTS
Additional versions are available, e.g. with a second Ethernet interface (for router/cloud-gateway use) or with an integrated LTE modem (for remote cloud communication). Not all combinations are technically possible; check the order code.

Technical specifications

• Model family: C4 (C4-A variants)
• Enclosure: DIN-rail and wall mounting; available sizes: 4MU, 8MU, 12MU; 45 mm front cut-out
• Power supply: wide-range 12–48 VDC
• Coprocessor: ARM® coprocessor for time-critical I/O and RS485 handling
• Coprocessor special functions: 96-bit serial number, 2 kB ferromagnetic RAM, RTC with backup capacitor, status LEDs, DIP switches
• Compute Module 4 interfaces: 1x Micro HDMI, 1x Ethernet, 2x USB 2.0
• RAM options (Compute Module): 2 GB / 4 GB / 8 GB
• Storage: 32 GB SD card with Linux OS
• Serial interfaces in the system: /dev/ttyACM0 (ASCII), /dev/ttyACM1 (MODBUS/RTU master), /dev/ttyACM2 (RS485 via USB)
• Analog I/O (AIOX): 4 / 8 / 16 channels; configurable as inputs/outputs (0/2–10 V, 0/4–20 mA), resistance measurement (0–1 MΩ), PT100/PT1000/NI1000
• Digital inputs: 24 V DC or dry contact
• Optional I/Os: relay outputs, LED strip drivers, temperature sensor inputs, shutter control
• Interface options: additional Ethernet interface or integrated LTE modem possible