Configuring a BACnet IP Data Source

Overview

BACnet IP is the standard protocol for building automation systems (HVAC, lighting, access control). This guide covers discovering BACnet devices on your network and reading their data points in Mango by Radix IoT.

Prerequisites

• Running Mango 4.x or 5.x with the BACnet module installed
• BACnet IP devices on the same network (or routable subnet)
• Knowledge of your network’s BACnet configuration (broadcast address, port)
• A BACnet local device already created in Mango (required before you can create a BACnet data source)

Step 1: Create a BACnet Local Device

Nothing else works until this exists. The BACnet/IP data source will not let you save without selecting a local device, and the page you create one on is not in the navigation menu — which is why this step is easy to miss.

The page is hidden from the navigation menu. Open Administration → Admin home and use the Utilities panel, which lists BACnet local devices. You can also go straight to /ui/admin/bacnet-local-devices. Reaching it needs the Edit local devices system permission.

1. Click Create new local device
2. Set the Local device ID — the BACnet instance number Mango itself presents on the network. It must be unique across the whole BACnet internetwork; a duplicate is a classic cause of erratic discovery
3. Set Local bind address (default 0.0.0.0) and Port (default 47808, the standard BACnet/IP port 0xBAC0). Broadcast address defaults to 255.255.255.255 and Subnet to 24
4. If the devices you need are on another subnet, fill in the BBMD address, BBMD port and BBMD registration interval (seconds)
5. Save the local device

Local bind address

This is the network interface Mango sends and listens on, and it is the single most common thing to get wrong.

On a server with one network card, the default is fine. On a multi-homed server — two NICs, a VM with several virtual adapters, a container host — the default can bind Mango to the wrong interface. Broadcasts then go out on a network with no BACnet devices on it, discovery returns nothing, and there is no error to tell you why. Set it explicitly to the IP address of the interface that faces your BACnet network.

BBMD address

BACnet discovery works by broadcast, and routers do not forward broadcasts. If your devices sit on a different subnet from Mango, a BBMD — BACnet Broadcast Management Device — is what carries broadcasts across the boundary.

Mango registers with it as a foreign device: you supply the BBMD’s address and port (default 47808), plus a registration interval (seconds) that controls how often Mango re-registers (default 300). Let the registration lapse and the BBMD stops forwarding, so discovery that worked yesterday quietly stops. Leave all three blank when Mango and the devices share a subnet.

You will select this local device when creating the data source in the next step.

Step 2: Create the BACnet Data Source

1. Navigate to Data integration > Data sources > + > BACnet/IP
2. Select the Local device you created above. This is required — the data source will not save without one
3. Set the remaining fields:

4. Click Save

Step 3: Discover Devices

1. Save the data source first, then open its Device browser tab — the tab is only active once the data source exists and has a local device selected
2. Click Start Who-Is. Mango broadcasts a BACnet Who-Is; Cancel Who-Is stops a scan in progress
3. Devices that respond appear in the list as they answer
4. Each device shows its instance number, name, and address. Use the filters — Device ID start, Device ID end, Vendor, Model, Name, MAC — to narrow a large result set

Step 4: Discover Objects on a Device

1. Select a discovered device
2. Select the device to load its Device objects — Mango queries it for all its BACnet objects:
   • Analog Input (AI) - temperature, humidity, pressure
   • Analog Output (AO) - setpoints, valve positions
   • Analog Value (AV) - calculated values
   • Binary Input (BI) - on/off status
   • Binary Output (BO) - commands
   • Binary Value (BV) - mode settings

Step 5: Add Data Points

For each object you want to monitor:

1. Select the object from the discovery results
2. Select the objects you want and use Add points. To add specific properties rather than whole objects, select them and use Add data points for selected properties
3. Configure which BACnet property to read (usually Present value)
4. Leave Use COV subscription off and poll instead. Change of Value sounds better than polling — the device pushes updates rather than Mango asking — but in practice most BACnet devices do not implement it correctly. Turn it on only for a device you have confirmed handles it, and expect to set COV lease time (minutes) so the subscription is renewed before it expires.

Step 6: Understanding BACnet Object Types

Mango lists object types by full name in sentence case — “Analog input”, “Multi-state input”, “Trend log”. The abbreviations below are the BACnet convention you will hear from controls engineers and see in device documentation; they are not what Mango displays.

Troubleshooting

No devices discovered

• Verify UDP port 47808 is open in your firewall
• Check the device is on the same subnet (or a BACnet router is configured)
• Try specifying the device IP directly instead of broadcast discovery
• Some devices have BACnet disabled by default - check device configuration

Timeout errors during object discovery

• Increase Timeout (ms) on the local device, not on the data source — Mango’s own error message says “try increasing your local device timeout setting”. The default is 6000 ms, with Retries at 2
• Raise Segment timeout (ms) (default 5000) as well for devices returning large segmented responses
• Some controllers with many objects can take 30+ seconds to respond
• Try discovering objects in smaller batches

COV subscriptions not working

• Not all devices support COV - fall back to polling
• COV requires the device to actively send updates - verify the device supports it for that object type