BL101 Industrial Gateway: Modbus RTU to Cloud via RS485 and Ethernet, with Data Retransmission after Network Outage

High O&M Costs for Legacy Modbus RTU Devices

In many manufacturing workshops, a large number of reliably operating devices (PLCs, instruments, VFDs, etc.) support only the Modbus RTU protocol and communicate via RS485 ports without native networking capabilities. Engineers must frequently travel to the site to download data using programming cables. This leads to rising travel expenses and fault response times that can stretch to hours or even the next day, severely impacting production efficiency.

How can you achieve low-cost data acquisition and remote O&M without stopping production or modifying device programs?

Direct Connection via RS485/232 Serial Ports – No Device Modification

The BL101 industrial IoT gateway is specifically designed to solve this problem. It features two RS485/RS232 serial ports with baud rates from 2400 to 115200 bps, adaptable to communication needs ranging from old meters to high-speed PLCs. The gateway acts as a Modbus RTU Master. Simply connect the device’s A/B wires to the serial port, then use configuration software to set register addresses, data types, and scaling factors – and you can start reading data. No modification to the device's original program is required, which is especially important for legacy equipment whose source code is lost or cannot be upgraded. A single BL101 can connect up to 10 devices and 512 data points, covering a small production line.

Mixed Acquisition with Dual Ethernet Ports and Serial Ports

In addition to serial ports, the BL101 provides one WAN port and one LAN port (10/100 Mbps, with built-in 2KV isolation transformer). It can directly connect to new-style PLCs or smart instruments that already have Ethernet interfaces. Serial devices and Ethernet devices can be mixed on the same gateway and expanded via cascading switches. The gateway truly unifies acquisition across both serial and Ethernet networks.

Protocol Conversion: Modbus RTU to MQTT JSON at the Edge

With traditional DTU transparent transmission, the cloud receives hexadecimal ciphertext that must be parsed by the user. This leads to low development efficiency and high data traffic. After southbound acquisition, the BL101 performs protocol conversion at the edge: it parses Modbus RTU messages into structured JSON data and then encapsulates them into standard MQTT protocol for uplink.

The gateway supports uplink to mainstream platforms such as Alibaba Cloud IoT, AWS IoT, and ThingsBoard. You only need to configure the MQTT broker address and reporting interval. The cloud no longer receives obscure data like 0x0104, but user-friendly JSON like {"temperature":25.5, "vibration":4.2}. This more than doubles the efficiency of upper-layer application development.

Data Retransmission: No Data Loss during Network Outage, Automatic Wired/4G Failover

Industrial site networks are often unstable (weak 4G signals, fiber construction interruptions, etc.). Traditional transparent transmission solutions simply lose data during outages, creating gaps in fault tracing. The BL101 provides dual protection:

• Local cache (Store-and-Forward): During a network outage, the gateway immediately stores time-stamped collected data in its 64 MB Flash memory. After the network recovers, it automatically retransmits the data, ensuring zero data loss.
• Automatic link failover: The gateway gives priority to wired networks (WAN port). When a wired interruption is detected, it switches automatically to the 4G backup link within milliseconds. When the wired network recovers, it switches back. The entire process is non-disruptive to operations.

For OEE analysis and fault timeline tracing, the store-and-forward mechanism ensures that all sampling points are fully delivered without any data holes.

Remote Operations and Maintenance

The BL101 supports remote configuration and firmware upgrades. Engineers can modify point mappings, serial port parameters, or reporting policies without visiting the site. Built-in hardware and software watchdogs can automatically restart the system if an anomaly occurs. A physical RESET button is provided to restore factory settings. According to actual project statistics, using the BL101 reduces monthly travel frequency by more than 80%, and fault response time shrinks from “next-day onsite visit” to minutes via “login to the cloud platform for remote diagnosis”.

Summary