DNP3 Guide

Overview

DNP3 (Distributed Network Protocol) is a SCADA protocol widely used to link control centers with RTUs and IEDs across electric, water, and oil & gas utilities. ControlBird provides DNP3 in two roles. The Master role acts as a client: it polls outstations, receives unsolicited events, and issues commands. The Outstation role acts as a server: it listens for master connections, exposes ControlBird tags as DNP3 points, and sends unsolicited responses.

Each role connects over TCP, serial (RS-232/RS-485), or TLS. You set everything up in the IO Manager app. Each DNP3 point is a tag with a dotted ID that is unique in your tenant, for example Substation.Feeder1.Current. See the IO Manager guide for the app as a whole.

Transports

Connect a DNP3 device

In the IO Manager, open the Tags section and choose Add tag to start Create Custom Device.

1. Pick the card for your transport: DNP3 TCP, DNP3 Serial, or DNP3 TLS, with the role Client (Master) or Server (Outstation).
2. Enter a Device Name and fill in the connection form: the host or listen address, port, and the link addresses below.
3. In the Points step, choose Add Point for each value. Give it a tag ID, a type, a source path, and a direction.
4. Finish the wizard. The connection starts and your tags show live values in the Tags section.

To expose a tag to an upstream master instead, create a Server (Outstation) connection, select the tag, choose Publish… on its detail, pick that connection, then choose Expose read-only, Expose with write-back, or Configure… to edit the tag ID and address first.

Link-layer addressing

DNP3 uses 16-bit link-layer addresses to tell the master from the outstation on a shared link. The master address defaults to 1 and the outstation address defaults to 1024. Both ends of a connection must use the same pair.

Tag source addresses

A DNP3 tag's source path names one point by its object group and point index, written ObjectGroup:Index. For example, AnalogInput:5 is analog input point 5. The index is a whole number from 0 to 65535.

Double-bit binary values map to a choice with four states: 0 = Intermediate, 1 = DeterminedOff, 2 = DeterminedOn, and 3 = Indeterminate.

The remaining point settings depend on the role:

• Master output points: a command mode, DirectOperate or SelectBeforeOperate.
• Outstation points: an event class, Class1, Class2, or Class3, for unsolicited reporting.

Polling and events

A DNP3 master combines periodic integrity polls (which request all data) with more frequent event polls (which request only changed data), plus optional unsolicited responses pushed by the outstation. The timing settings on the connection form are:

Unsolicited response classes

Outstations can push events without being polled. Each event carries the class set on its tag: Class 1 (urgent), Class 2 (normal), or Class 3 (background). Unsolicited reporting is on by default and can be turned off per class on the connection form. An outstation's event buffer holds 100 events by default.

Examples

Master over TCP

Host:               192.168.1.100
Port:               20000
Master address:     1
Outstation address: 1024

Tag: read an analog input

Tag ID:      Substation.Feeder1.Current
Source Path: AnalogInput:5
Direction:   Read

Tag: command a binary output

Tag ID:       Substation.Breaker1.Close
Source Path:  BinaryOutput:0
Direction:    Write
Command mode: SelectBeforeOperate

Notes

• The TLS transport has a skip certificate verification setting that bypasses peer certificate validation. Leave it off in production.

For a hands-on introduction to connecting a device, see walkthrough step 6: Connect Your First Device.