// serial field devices

Real MS/TP,
not just IP

Most BACnet tools stop at BACnet/IP. The field devices — VAV boxes, room controllers, thermostats — are frequently MS/TP only, sitting on an RS-485 segment no IP scanner will ever see. BACManager includes a full MS/TP master-node implementation: it joins the token ring and talks to those devices directly.

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Windows 10/11 · RS-485 master node · 9.6k–115k baud · 14-day trial

// the setup

Open a segment in three fields

Switch the datalink to MS/TP and the connection panel swaps IP fields for serial ones.

🔌 Serial port

Point a USB-RS485 adapter at the segment and pick its COM port from the list — refresh if you plug it in after opening BACManager.

⏳ Baud rate

Match the segment's configured speed: 9600, 19200, 38400, 57600, 76800 or 115200. Every node on an MS/TP segment must agree on this.

🔒 MAC address

This station's MS/TP MAC (0–127), which must be unique on the segment — a conflicting MAC causes token-passing errors for everyone on the line.

// what "master node" means

A real station, not a sniffer

Some tools only passively listen on MS/TP, decoding traffic other masters generate. BACManager actually joins the token ring: it answers Poll-For-Master, takes its turn holding the token, and sends confirmed and unconfirmed service requests exactly as a native MS/TP controller would. That is what makes writes, COV, and the Schedule/Calendar editor work over MS/TP — a passive listener can only ever read what happens to pass by.

// once it's open

Everything works the same as over IP

The point of a real master node is that nothing downstream needs to know the datalink is serial.

🔍

Discover

Run whoIs over the segment the same way as over BACnet/IP — every MS/TP device that answers appears in the device list.

📁

Browse & write

Full object list, property read/write, and priority arrays for commandable points — identical to the IP-side property browser.

📅

Schedule & Calendar

The same weekly-grid schedule editor opens for a Schedule object found over MS/TP as for one found over IP.

// mixed sites

MS/TP and Modbus RTU, side by side

MS/TP and Modbus RTU each need their own COM port, so a common setup on a mixed site is one USB-RS485 adapter for the BACnet MS/TP segment and a second for the Modbus RTU meters or drives — both live in the same BACManager window at once, no switching applications or unplugging adapters mid-commissioning.

Modbus register table in BACManager polling an AHU supply fan controller, with live values and a description column — The same window's Modbus side, for the RTU meters that share the panel with MS/TP controllers

// questions

MS/TP — FAQ

What hardware do I need for MS/TP?+

A USB-RS485 adapter connected to the MS/TP segment. Pick the serial port, a baud rate that matches the segment (9.6k to 115k), and a free MAC address (0-127) not already used by another node.

Is this a real MS/TP master, or just passive listening?+

A real master node. BACManager joins the token ring, answers Poll-For-Master, and sends confirmed and unconfirmed requests exactly as a native MS/TP device would — not a sniffer.

Do discovery and the property browser work the same as over IP?+

Yes. Once the MS/TP connection is open, Discover, the property browser, the Schedule and Calendar editor, and EDE/CSV export all work identically to BACnet/IP.

Can I run MS/TP and Modbus RTU at the same time?+

Yes, on separate COM ports. A common setup is one USB-RS485 adapter for the MS/TP segment and a second for Modbus RTU meters or drives on the same site, both live in the same BACManager window.

What if my MS/TP MAC address conflicts with an existing device?+

Pick an unused MAC in the 0-127 range before opening the connection — a conflicting MAC will cause token-passing errors on the segment. Check the segment's existing device list if you are unsure which addresses are free.

Connect to your MS/TP segment today

Download the free trial and open a real RS-485 connection — no credit card, no cloud.