Devices in a factory workshop never coordinate before speaking. PLCs use Modbus RTU, sensors talk RS485, meters run TCP, and several field buses operate independently. To unify all this data on a cloud platform, the first step is connecting them to an industrial edge gateway.
This article walks through the process using PUSR M300 as a reference.
Before wiring anything to the gateway, list every device with four pieces of information:
This list determines how many serial ports and Ethernet ports the gateway needs, and how complex the protocol conversion will be.
PUSR M300 provides 1× RS232/485, 1× RS485, 2× Ethernet ports (1 WAN/LAN + 1 LAN), plus 2× DI and 2× DO digital inputs and outputs. Wiring breaks down into three steps:
Connecting Serial DevicesPLCs and most sensors connect via RS485. RS485 bus supports daisy-chained multi-device topology—A to A, B to B, with a 120Ω termination resistor at each end to eliminate signal reflection. M300's two RS485 ports can each serve devices in different workshop areas, preventing excessive bus load.
Connecting Ethernet DevicesMeters supporting Modbus TCP or PLCs with Ethernet ports plug directly into the LAN port. If the site only has ADSL or fiber connectivity, the WAN port accepts 4G or wired broadband input.
Connecting DI/DO SignalsLimit switches, water level sensors, and other on/off signals connect to DI terminals; relay-based control outputs connect to DO terminals. M300 supports up to 2,000 data collection points, sufficient for small to medium production lines.
After wiring, the gateway's core job is protocol conversion. On-site devices speak many languages, but cloud platforms typically only need standard MQTT or TCP data.
Serial Devices (Modbus RTU)In the gateway's configuration interface, set baud rate, data bits, stop bits, and parity for each RS485 port. Then add Modbus register addresses for each device—for example, a temperature sensor at register 40001 with a 5-second collection interval. The gateway automatically converts RTU frames into internal data structures.
Ethernet Devices (Modbus TCP)After assigning an IP address to the LAN port, the gateway polls the meter's IP and port to read holding registers. With many meters on one network, group polling schedules to avoid congestion.
Custom ProtocolsIf on-site devices use non-standard protocols, M300 supports Node-RED graphical programming. Drag-and-drop nodes to build data mapping logic without writing code from scratch. Once Node-RED outputs MQTT messages, data flows directly to the cloud.
After data is collected, two reporting approaches are available:
Real-Time PushSet trigger conditions such as temperature exceeding a threshold or liquid level dropping below a minimum. The gateway immediately pushes alarm messages via MQTT. M300's built-in alarm function notifies on exceptions as they occur.
Scheduled CollectionFor routine data, set reporting intervals of 30 seconds or once per minute. Reporting channels—4G, Ethernet, or ADSL—can be selected based on on-site network conditions.
PUSR M300 supports the standard MQTT protocol and connects directly to major cloud platforms including Alibaba Cloud, AWS, ThingsBoard, and Azure. After configuring the MQTT Broker address, port, and authentication credentials, define the upload topic (topic) and data format (JSON).
When using PUSR's cloud platform or open-source platforms like ThingsBoard, device templates can be configured directly on the gateway, reducing adaptation work on the cloud side.
Installation MethodM300 supports DIN rail mounting and wall mounting. DIN rail suits fixed installation inside electrical cabinets; wall mounting works for temporary on-site debugging. The enclosure achieves IEC61000-4-3 Level 3 EMC protection, ensuring stable operation in industrial electromagnetic environments.
Operating TemperatureWide temperature range of -25°C to 75°C covers both unheated winter workshops and air-conditioning-free server rooms.
Power SupplyDC 9~36V wide-voltage input; 24V DC is the most common. Power loss does not erase configuration. The gateway re-establishes connections automatically on power recovery.
Network SecurityPUSR devices carry 3C, CE, FCC, ROHS certifications and comply with EU EN 18031 cybersecurity standards. The gateway's built-in firewall restricts unauthorized IP access to serial or Ethernet ports.
A factory automation engineer faced a common problem during a workshop upgrade: three PLCs from different brands, two temperature and humidity sensors, and four power meters, all with incompatible protocols. The solution deployed M300 as the edge gateway—RS485 port 1 connected to three PLCs, RS485 port 2 to sensors, LAN port to power meters, and WAN port uploading via 4G to Alibaba Cloud IoT platform. The entire setup took less than half a day. Adding new devices afterward required only a configuration change on the gateway, with no rewiring needed.
Another scenario is a distributed pump station monitoring system. Five stations spread across 30 kilometers, each equipped with an M300. DI collects water level switch status, AI collects flow analog signals, and 4G relays data back to a central control room. After system launch, liquid level data that previously required manual rounds is now updated automatically every minute.
Connecting PLCs, sensors, and meters to an industrial edge gateway follows four steps:
Once hardware is in place and protocols are connected, adding new devices requires only configuration changes—no rewiring. This approach applies to small and
