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RMG/941C: Remote Maintenance Gateway with CAN

Remote Maintenance Gateway RMG/941C

The RMG/941C offers a CAN 2.0A/2.0B as well as a 10/100 Mbps Ethernet LAN interface and is also available in a variant with a 4G LTW modem (RMG/941CL) or with an NB IoT wireless modem (RMG/941CN).

With the extensive software equipment and the function extensions via subsequently installable apps, CAN applications and CAN modules can be integrated into the Internet of Things and Industry 4.0 environments.

Thus, the following applications can be realized with the RMG/941C for example:

  • IoT integration of any CAN data via CAN-2-MQTT including cloud connection for Amazon, Google, Microsoft and other IoT platforms
  • Connect individual CAN networks locally or globally via CAN-over-IP bridge using UDP and IP protocol
  • VPN-secured remote access to CAN networks and individual CAN nodes via OpenVPN
  • CAN data analysis via supervised machine learning (TinyML), e.g. for condition-based monitoring and predictive maintenance
  • CAN sensor bus: network with individual CAN sensors via simple 4-wire bus system (one wire pair each for the CAN bus and for poqer supply of the individual CAN sensors)
  • CAN application development via C/C++, Python and JavaScript (Node-RED)
  • Secure remote software updates for CAN devices (SDU = secure device update)

The runtime environments for C/C++, Python, Node.js and Node-RED integrated in the RMG/941C also enable many other possible applications.

The embedded Linux operating system based on Debian also allows the installation of additional software (apt-get) as well as secure over-the-air (OTA) software updates.

Software Development Kits (SDK)

With C/C++, Python, Node.js and Node-RED, various options are available for developing your own applications and executing them on the RMG/941C. Some special features have to be considered, which are explained in the following.

C/C++

Since C/C++ is a compiler language, a cross-development environment is required. This is used to edit the source code on a PC and translate it with a cross compiler into an executable binary file. This binary is then copied to the file system of the RMG/941C.

As a cross-compiler, we have developed an SSV cross-build Docker, which is available via a Docker Hub repository. Application-specific variants can be created from this cross-build Docker, e.g. to include special libraries.

Python und Node.js

Both are interpreter languages where the respective Python or JavaScript source code is edited on a PC and then transferred to the file system of the RMG/941C as a text file with the corresponding file extension (i.e. *.py or *.js) and executed there.

It should be noted that neither the Python package manager PIP nor the Node.js package manager NPM are available on the RMG/941C. These tools are not suitable for use in embedded systems, since otherwise, the control over the components and thus the integrity of the file system can be lost.

Node-RED

This graphical development tool with integrated runtime environment can also be classified as an interpreter language, because Node.js is used to execute the Node-RED flows.

The Node-RED-internal Palette Manager for the subsequent installation of further nodes cannot be used on the RMG/941C either, because the respective dependencies can cause various problems in the file system of the embedded Linux, analogous to PIP and NPM.

In-System-MQTT-Broker

An In-System MQTT broker (ISMB) is available for communication between the individual applications. It enables the applications isolated in individual processes to exchange data bidirectionally via MQTT. The ISMB can be reached via the IP address 127.0.0.1 (local host) and the TCP port 7883.

Via ISMB, for example, a Python application for CAN data acquisition can communicate with a Node-RED application. A possible use case would be a Node-RED dashboard as a user interface to send configuration data to the Python application.

Information at GitHub

An introduction to the SDKs including links to the required resources can be found on SSV's GitHub page: SDK's for the RMG/941C on GitHub

We also offer a one-hour on-demand webinar for getting started with these SDK's, which can be requested through our sales department.

Expandable Functions via Apps

Certain functions for the RMG/941C can also be easily and conveniently upgraded as an app via the configuration interface (SSV/WebUI), for example a node for Node-RED to connect an SQLite database.

 

Show list of currently available apps

Highlights

  • CAN and LAN interface
  • Optional with LTE or NB IoT modem
  • C/C++, Python and JavaScript runtime environment
  • Extensive machine learning components
  • Data flow programming with Node-RED
  • CAN real-time data analysis via machine learning
  • IoT connectivity plus PKI/TLS security
  • Function extensions via app

LTE Router

Secure Internet connection via LTE mobile communications

The RMG/941CL can be used as an LTE router, for example to transfer data from a local area network (LAN) to another IP network, usually the Internet.

Thus, an RMG/941CL as LTE router enables local network devices to access the Internet and at the same time prevents access from the Internet to the local network by an internal firewall for security reasons.

User story LTE router

When certain events occur, the controllers of our frequency inverters are to send measured values to a database server on the Internet via the PROFINET LAN interface.

The DNS name of this server is preconfigured in the inverters at the factory. Because of this, we only need Internet access via LAN.

IoT Applications

Secure Internet connection for IoT applications

The secure Internet connection for IoT applications is only established when required, either via the LAN interface or via the 4G mobile network (LTE), i.e. when an IoT application wants to send data via MQTT or HTTP request, for example.

The RMG/941CL itself is virtually invisible on the Internet and cannot be reached by other applications from the outside.

User story IoT application

The assemblies of our maintenance contract customers transmit system messages, operating hour counters and level measurements for individual operating materials to an IoT service.

We use this to plan and coordinate maintenance appointments, spare part requirements and other types of service work.

VPN Gateway

Secure remote access via VPN

A virtual private network (VPN) is a specially protected network environment that can only be accessed by systems prepared by special measures (e.g., by installing special drivers plus valid access certificates).

In practice, VPNs often use the Internet as a transport channel. The VPN protocols used in each case employ encryption, which enables tap-proof and tamper-proof communication between the VPN partners.

User story VPN

The CAN sensor technology of our systems includes a web-based configuration and monitoring dashboard that runs directly on site on the gateway and which our customers can access via the LAN interface using a web browser.

A highly secure VPN remote access option exists for our service via the Internet.

OpenVPN Server in a Docker

For testing and evaluation purposes, we put a simple OpenVPN server into a Docker container and published it on GitHub.

OpenVPN server on GitHub

OTA Update Gateway

Secure Over-the-Air updates

For the RMG/941C, a task-related OTA update agent is required that loads the updates from the server and transmits them, e.g., via ISO-TP (ISO 15765-2) to the individual CAN devices.

To ensure the necessary cybersecurity of such an OTA update solution, a public key infrastructure (PKI) with digital signatures is required.

An SSV Secure Device Update (SDU) server can be used as an update server for an OTA update solution.

On GitHub you can find an API description for the SDU server.

User story OTA updates

Our battery monitoring systems have an externally accessible CAN interface that can be used to program firmware binaries into the flash memory of the microcontrollers of these assemblies. Up until now, this update possibility is used by our service technicians with the help of a PC plus a USB-CAN adapter.

With the RMG/941C, we will automate this update task. In the future, a software agent on the gateway will detect that an update is available for a specific board, load the update file from the Internet and program it into the microcontroller's flash.

CAN-over-IP Bridge

Connecting CAN networks via Ethernet or mobile radio

To use the CAN-over-IP bridge, two RMG/941C are required, on each of which the can2udp app must be installed.

The necessary settings during commissioning (CAN bit rate, UDP port, IP addresses) are made via the SSV/WebUI.

User story CAN-over-IP

We have numerous CAN sensor networks for building automation in use in several buildings on our premises.

We would like to connect these individual CAN segments with each other using Ethernet LAN networks in order to be able to collect the data centrally.

MQTT-to-Anything

Using MQTT locally in OT Environments

The number of components in an automation landscape that communicate locally via MQTT is constantly increasing. However, the required MQTT broker is often operated in the IT world or on a high-end edge platform.

Using the RMG/941 internal Mosquitto MQTT broker and corresponding interface agents, the data of different protocols can be directly converted into MQTT topics and integrated into automation applications.

User Story MQTT-to-Anything

We have various assemblies in our plants that communicate via MQTT. However, the required broker is located in our IT. This now results in a security problem, since OT and IT form different network segments and are separated from each other via an intelligent firewall.

We need an MQTT broker directly on site in the plant. In addition, it would be desirable if we could also establish a connection between the CAN and Modbus interfaces of some control modules and the MQTT data points of our visualization.

Technical Data

Single Board Computer
Model DIL/NetPC DNP/9535
Processor
Manufacturer / Type Atmel ATSAM-A5D35 SoC
Clock speed 528 MHz
Storage
RAM 256 MB SDRAM
Flash 4 MB NOR
Storage medium 1x internal SD-card holder
Interfaces
Ethernet 1x 10/100 Mbps (RJ45)
CAN I/Os 1x CAN 2.0A/2.0B (screw terminal)
supported bitrates (Kbps): 50/100/125/250/500/1000
COM (service port) 1x 6-pin connector
Antenna 1x SMA interface for LTE/NB-IoT antenna
Special functions
Real time clock (RTC) 1x RTC with internal battery backup
Watchdog 1x Timer watchdog
(Hardware-based, Software-configurable)
1x Power supervisor (Hardware-based)
SIM-Card 1x Holder for Mini-SIM-cards (accessible from the outside)
LTE-Modem (RMG/941L)
Mobile radio standards GSM/UMTS/HSPA+/LTE
Transfer rates 100 Mbps max. download, 50 Mbps max. upload
Frequency bands LTE: B1/B3/B5/B7/B8/B20
WCDMA: B1/B5/B8
GSM/GPRS: GSM850/GSM900/DCS1800/PCS1900
Authentification PAP, CHAP, CHAT, none
Supported APNs Telekom, Vodafone, 02, E-Plus, user-defined
NB-IoT-Modem (RMG/941N)
Mobile radio standards GSM/LTE
Transfer rates LTE Cat M1 375 Kbps max. download, 375 Kbps max. upload
Transfer rates NB-IoT (LTE Cat NB1) 32 Kbps max. download, 70 Kbps max. upload
Transfer rates GSM GPRS: 107 Kbps max. download, 85,6 Kbps max. upload
EDGE: 296 Kbps max. download, 236,8 Kbps max. upload
Frequency bands LTE Cat M1 LTE FDD: B1/B2/B3/B4/B5/B8/B12(B17)/B13/B18/B19/B20/B26/B28
LTE TDD: B39
Frequency bands NB-IoT (LTE Cat NB1) LTE FDD: B1/B2/B3/B4/B5/B8/B12(B17)/B13/B18/B19/B20/B26/B28
Frequency bands GSM/GPRS: GSM850/GSM900/DCS1800/PCS1900
Authentification PAP, CHAP, none
Supported APNs 1nce
Displays / control elements
LEDs 1x Power
1x System status (programmable)
2x LAN LED for Ethernet interface
Electrical characteristics
Supply voltage 11 .. 28 VDC from external power supply
Power consumption < 15 W
Mechanical characteristics
Protection IP20 industrial housing for 35 mm DIN-rail
Mass < 150 g
Dimensions 112 mm x 100 mm x 22,5 mm
Operating temperature 0 .. 60 °C
Storage temperature -40 .. 85 °C
Standard and certificates
EMC CE
Environmental standards RoHS, WEEE

Product Variants

Name Description
RMG/941C Without LTE modem, without antenna connection
RMG/941CL With LTE modem and antenna, without SIM card
RMG/941CN With NB-IoT modem, antenna, and preinstalled SIM card

SSV Software Systems GmbH

Dünenweg 5
30419 Hannover

Phone: +49(0)511 / 40 000-0
Fax: +49(0)511 / 40 000-40

sales@ssv-embedded.de


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