Unlock Your Modbus Data with Digi Modbus Sparkplug

Bringing Modbus Into the Modern IIoT World

If you're working with industrial equipment in the field, there's a good chance Modbus is already part of your world. From PLCs to drives, meters, and flow controllers, the list of Modbus-speaking devices in any industrial installation is long. The protocol works. It's proven. But it was never designed for the connected, data-hungry world that modern operations teams now need to navigate.

That's where Digi Modbus Sparkplug comes in.

What Is Digi Modbus Sparkplug?

Digi Modbus Sparkplug is a Python-based application that allows users to poll Modbus registers from devices connected to Digi hardware and send that Modbus data in Sparkplug format to a given MQTT broker. It runs as a subscription-licensed, value-added service (SKU: DG-PSPY-MBSP) directly on any Digi DAL OS device, adding a capability that doesn't exist natively on any of these platforms out of the box. No additional servers, middleware, or custom scripting are required.

The Hardware It's Built For

Digi Modbus Sparkplug runs on any Digi DAL OS device, but three product families represent the most common deployment scenarios in industrial environments.

Digi IX25 — Next-generation 5G Industrial Router

Digi IX25 is a purpose-built industrial router solution for enterprises and critical infrastructure that require secure, reliable, always-on connectivity. IX25 is designed primarily for utilities, energy, manufacturing, transportation, and distributed retail networks. Managed with SOC 2, Type 2 verified Digi Remote Manager (DRM), IX25 is easy to manage at scale.

Physical interfaces include four Gigabit Ethernet ports, a single RS-232/485 serial port, and a USB-C port, with DIN rail mounting and an IP30 ingress protection rating. IX25 operates from -40 °C to +75 °C and carries certifications including C1D2, ATEX, E-Mark, and MIL-STD-810H. For engineers deploying into demanding environments where Modbus devices need to feed into modern IIoT platforms over a fast, resilient WAN link, IX25 provides that connectivity along with the edge compute headroom to run Modbus Sparkplug natively.

Digi IX30 — Proven 4G LTE Industrial Router

Digi IX30 is an intelligent 4G LTE router with Ethernet, serial I/O, and Modbus bridging built in, along with patented Digi SureLink technology, VRRP+, and dual SIM slots for an extremely resilient cellular connection. Like all Digi cellular solutions, IX30 fully integrates remote monitoring, management and rapid firmware updates via DRM.

Additionally, Digi IX30 features dual Ethernet ports, an RS-232/422/485 serial port, digital and analog I/Os, a rugged IP30 aluminum enclosure, and integrated industrial edge computing for hosting containerized applications and custom solutions. IX30 is already widely deployed across critical infrastructure worldwide, making it a natural fit for adding Modbus Sparkplug capability to existing installations without touching the underlying hardware.

Digi Connect EZ — Dedicated Serial Device Servers

For sites where the primary requirement is bridging serial Modbus devices onto the network, without the footprint or cost of a full cellular router, the Digi Connect EZ family is the purpose-built answer. Digi Connect EZ is a click-to-connect solution that integrates Digi Remote Manager for rapid configuration and ongoing management.

Digi Connect EZ is available with 1, 2, or 4 serial ports, software-selectable for RS-232, RS-422, and RS-485 communication, with optional LTE, Wi-Fi, and industrial specifications including extended temperature and C1D2 rating. Running Digi Modbus Sparkplug on a Connect EZ server transforms it from a serial-to-network bridge into an active IIoT data publisher — delivering Sparkplug B payloads to your MQTT broker directly from the device, with no additional infrastructure.

Flexible Connectivity: TCP and Serial Modbus

Real-world Modbus infrastructure is rarely uniform. Some devices communicate over Ethernet via Modbus TCP. Others sit on RS-232 or RS-485 serial buses running Modbus RTU or ASCII. Digi Modbus Sparkplug handles both, allowing a single deployed device to poll registers across your mixed Modbus environment and publish everything through one unified MQTT stream.

This matters in practice. A single installation might have a TCP-connected PLC alongside RS-485 serial devices on one or more buses. Modbus Sparkplug bridges all of it to the same broker, under the same structured Sparkplug namespace.

Why Sparkplug B? Because Not All MQTT Is Equal.

Publishing data to MQTT is easy. Publishing it in a way that downstream systems can reliably consume, at scale, without custom integration work for every new subscriber is the harder problem Sparkplug B solves.

Built on top of MQTT, Sparkplug B defines a standardized topic namespace, device session lifecycle management via birth and death certificates, and efficient binary encoding using protocol buffers. What that means practically: your broker receives structured, self-describing payloads that any Sparkplug-aware platform can consume immediately, whether that's Ignition SCADA, AWS IoT, Azure IoT Hub, a custom historian, or your own analytics pipeline. The integration work happens once. New subscribers connect to the same stream without rework.

The application supports enhanced data processing in Sparkplug format, enabling visualization of your data by sending it to Sparkplug MQTT servers.

Read and Write: Bidirectional Modbus Control

Most edge data solutions stop at read-only visibility. Digi Modbus Sparkplug supports writing values back to connected Modbus devices via the same MQTT interface, enabling closed-loop workflows and remote control from upstream systems.

For OT engineers, this opens up practical use cases that go well beyond monitoring:

• Pushing setpoint changes to drives and controllers from a cloud SCADA or manufacturing execution system
• Remote commissioning and parameter configuration without dispatching a technician to the field
• Automated control responses triggered by upstream analytics or alarm management systems
• Fleet-wide configuration updates across distributed sites from a central operations center

Smarter Data, Lower Bandwidth Costs

For deployments on cellular connections, which is a common scenario on both Digi IX25 and IX30, bandwidth efficiency directly affects operating costs. The application enables reporting by events and exceptions rather than heartbeat reporting, keeping data costs low by sending only important data. Instead of flooding your MQTT broker with constant polling output on a fixed interval, you get intelligent, change-driven publishing: relevant data when it matters, not noise all the time.

The Bottom Line

Digi Modbus Sparkplug gives OT engineers a production-grade, supported path to unlock the data in their Modbus devices and deliver it in a modern, standards-based format to any system that needs it without replacing hardware, writing custom code, or locking into a proprietary platform. Whether you're adding a new IX25 to your network and pushing data over 5G from a utility substation, deploying a field-proven IX30 in an industrial cabinet with a mix of serial and networked Modbus devices, or using a Connect EZ to bridge RS-485 serial equipment directly to your network, Modbus Sparkplug runs natively and handles the translation to Sparkplug B automatically.