EOE-W55RP20_BACnet Module

Overview

The EOE-W55RP20_BACnet module is an embedded Ethernet module that connects your equipment to a BACnet building automation network. It is built on the WIZnet W55RP20, which combines an RP2040 MCU and a W5500 Ethernet controller in one package. The host MCU only exchanges AT commands over UART. BACnet protocol processing, BACnet/SC TLS encryption and certificate authentication, and TCP/IP are all handled by the module, so the host MCU does not need a BACnet stack or a network stack.

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Why EOE-W55RP20_BACnet

When to Use

• You need to connect existing equipment to a BACnet building management system (BMS)
• You are joining an existing BACnet/IP site and also need to be ready for BACnet/SC (secure BACnet)
• The host MCU has no room for a BACnet stack, a TCP/IP stack or TLS
• You want to shorten the time spent on Ethernet hardware design and protocol testing

Advantages

A lighter host MCU

The module handles BACnet and TCP/IP; the host only exchanges values over UART. Even a small MCU can become a BACnet device.

BACnet/IP and BACnet/SC in one module

With a single setting, the same module becomes a BACnet/IP device or a BACnet/SC device that communicates over TLS through a hub. If the site moves to SC, the hardware does not need to change.

Writes the host decides

Objects that trigger a real action, such as a relay, can be made confirmed: when a workstation writes a value, the module asks the host MCU first and applies it only after approval. If the host refuses, the reason reaches the workstation as a BACnet error.

Stable connections

TCP/IP is handled by the W5500 chip, not by software. Connection management, retransmission and buffering happen inside the chip, so communication continues while the firmware is busy with other work.

Updates that fail safely

New firmware is verified, held in a staging area and installed at the next boot. If the transfer is interrupted or the file is damaged, the running firmware stays in place, and firmware for another product is refused.

Safe factory defaults

Out of the box both BACnet and the web interface are disabled, so the module announces nothing over BACnet and opens no web server until it is configured. A factory reset erases the BACnet/SC private key first.

Your product's identity

The Vendor_Identifier, Vendor_Name and Model_Name a workstation reads can be set to the end-product manufacturer's values. The factory default is WIZnet's Vendor ID 1697. Each module has a unique MAC address written at the factory, and the default Device instance is derived from this MAC as well.

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Supported Hardware

This firmware (1.0.0) runs on the following W55RP20-based hardware. To purchase, contact direct@wiznet.io.

WIZ-IP20	W232N	EOE-W55RP20
Mag Jack module 3.3 V TTL UART	DIN-rail converter RS-232 (D-SUB9)	Castellated module 3.3 V TTL UART

Key Features

• BACnet/IP (Annex J) device, or BACnet/SC (Annex AB) hub connector over TLS 1.3
• ReadProperty, ReadPropertyMultiple, WriteProperty, WritePropertyMultiple, SubscribeCOV and device management services
• Up to 256 objects of nine types (Analog, Binary and Multi-state Input, Output and Value), defined with AT commands or registered at once from a CSV file
• Confirmed writes: the host MCU approves a value written from a workstation before it is applied
• 10/100 Mbps Ethernet with TCP/IP handled by the W5500 hardware, DHCP or static address, DNS
• 4 TCP/UDP channels for the host MCU, in addition to BACnet
• 56 AT commands and a web interface for every setting
• Firmware update over the web interface or UART, verified before installation
• Diagnostics, watchdog, and factory reset by AT command, web interface or pin

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Feature Details

BACnet/IP

• Operates as a BACnet/IP (ASHRAE 135 Annex J) device. The default UDP port is 47808.
• Workstations find the device and its objects with Who-Is/I-Am and Who-Has/I-Have.
• Registers with a BBMD as a Foreign Device, for workstations on other subnets.
• Broadcasts are either subnet-directed (default) or global (255.255.255.255).

BACnet/SC

• Operates as a BACnet/SC (ASHRAE 135 Annex AB) hub connector. Because it goes through the hub, it communicates regardless of subnet, even across the internet or between buildings.
• Connects with WebSocket over TLS 1.3 (wss://), and the two sides authenticate each other with EC P-256 certificates.
• A primary hub and a failover hub can be registered. When the primary is lost the module moves to the failover hub, and when the primary comes back it returns to it.
• The private key, device certificate and issuer certificate are uploaded with AT commands or on the web interface. The private key never leaves the module.
• You can choose how certificate validity periods are judged while the clock is unknown (LENIENT / STRICT), and whether the hub certificate's name is checked.

BACnet/IP and BACnet/SC are alternatives: you choose one of the two. They are not used at the same time.

BACnet Services

• ReadProperty, ReadPropertyMultiple, WriteProperty, WritePropertyMultiple
• SubscribeCOV — 16 subscriptions, confirmed and unconfirmed notifications
• DeviceCommunicationControl, ReinitializeDevice — can be protected by a password
• TimeSynchronization, UTCTimeSynchronization
• Implements the services of the BIBBs in the BACnet Application Specific Controller (B-ASC) profile (DS-RP-B, DS-WP-B, DM-DDB-B, DM-DOB-B, DM-DCC-B). Protocol_Revision is 22.

Objects

An object is a single value that a workstation reads or writes, such as a temperature, a damper position or a fan run command.

• Up to 256 objects, of which up to 64 can be commandable objects with a priority array.
• Nine types: Input, Output and Value of Analog, Binary and Multi-state.
• The Device object and the Network Port object exist from the start, so communication can be checked before any object is created.
• Each object is set as accepting remote writes or not, as keeping its value across reboots or not (PERSISTENT), and as needing the host's approval for writes or not (confirmed).
• To register many at once, upload a CSV file on the web interface. The CSV also sets properties such as the write range, COV increment, description and polarity.
• The host can send the Reliability along with the value. While a workstation holds an object Out_Of_Service, the workstation sets its value.

Time

• Time comes from the workstation's TimeSynchronization, from an SNTP server, or from both.
• You set the Device's UTC_Offset. For Korea it is UTC+09:00.

Network

• 10/100 Mbps Ethernet, with TCP/IP handled by the W5500 hardware.
• DHCP or a static address. DNS is supported.
• Besides BACnet, the host MCU has 4 TCP/UDP channels of its own. Each send carries up to 1460 bytes, and host names can be used to connect. The Ethernet chip's sockets are shared with BACnet and the web, so check how many can be open at the moment with AT+SOCKAVAIL?.

Configuration & Management

• 56 AT commands cover all settings. The module also sends unsolicited messages (URCs) when its state changes, for example on a remote write, a time synchronization or a hub connection.
• The same settings are available on the web interface, with Dashboard, Network, Identity, BACnet, BACnet/IP, BACnet/SC (including certificate upload), Objects, Object mapping (CSV), Firmware, Diagnostics, Account and Maintenance pages.
• The web interface requires a login. The password must be at least 8 characters; repeated wrong passwords lock the login for a while, and idle sessions expire.
• The web interface is disabled by default. Set a password over AT, then turn it on.
• AT and the web apply the same checks to the same settings, so either way gives the same result.

Firmware Update

• Upload the file on the web interface, or send it over UART with an AT command.
• Received firmware is verified, held in a staging area and installed at the next boot.
• Firmware for another product, damaged files and files that are not runnable firmware are refused during verification.
• Settings, objects, stored values and BACnet/SC certificates are kept through an update.

Diagnostics

• BACnet request counts, B/IP and SC connection state, confirmed writes and COV, time synchronization, sockets, storage and serial port state can be queried at once.
• If the Ethernet chip stops responding or loses its configuration, the module recovers it and counts how often that happened.
• If BACnet processing stalls or an Ethernet chip recovery does not finish, the watchdog restarts the module. The reason for the last restart can also be read as the Device's Last_Restart_Reason.
• Factory reset is available over AT, on the web interface and with a dedicated pin. The MAC address, serial number and product ID are kept.

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Documentation

This section provides the reference documentation for the module's AT command interface and its BACnet conformance.

Title	Description	Link
AT Command Guide	All 56 AT commands, responses, URCs and error codes	EN
PICS	BACnet Protocol Implementation Conformance Statement (ASHRAE 135 Annex A): BIBBs, objects and properties, data links	EN

Setup & Configuration

This section provides step-by-step guides for connecting the module, setting up BACnet and updating the firmware.

Title	Description	Link
Getting Started Guide	Step-by-step guide from wiring to reading a value from a workstation	EN
BACnet Setup Guide	BACnet/IP and BACnet/SC setup, object definitions (AT · CSV), confirmed writes, time, Foreign Device	EN
Firmware Update Guide	Updating the firmware through the web interface or AT commands (UART)	EN

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Specifications

Item	Value
User objects	256 (up to 64 of them commandable)
COV subscriptions	16
Confirmed writes waiting at once	4 (host approval time 750 ms)
Max_APDU_Length_Accepted	BACnet/IP 1024 · BACnet/SC 1476
BACnet/SC hubs	primary 1 · failover 1
TCP/UDP channels	4 (how many can be open at once: AT+SOCKAVAIL?)
Socket send size	1460 bytes
AT command line	255 bytes

Hardware Connections

Signal	EOE-W55RP20	WIZ-IP20	W232N	I/O	Description
AT command port	GP4 (TX) · GP5 (RX)	P5 (TXD) · P3 (RXD)	DB9 3 (TXD) · 2 (RXD)	O · I	115200 8N1 by default, no flow control
AT port flow control	GP6 (CTS) · GP7 (RTS)	P6 (CTS) · P10 (RTS)	DB9 8 (CTS) · 7 (RTS)	I · O	Connect only if flow control is used
Handshake	GP8 (DTR) · GP9 (DSR)	None	DB9 4 (DTR) · 6 (DSR)	I · O	DSR high means the module is ready for commands
Status outputs	GP10 · GP11	P13 (LINKLED) · None	LINK · TCP LEDs	O	Ethernet link · TCP connection present
Factory reset input	FACT RSTn (GP18)	None	Switch inside the case	I	Internal pull-up. Hold low for 5 s or more to reset
Debug console	GP0 (TX) · GP1 (RX)	None	None	O · I	921600 8N1, separate from the AT port

• The W232N's DB9 is at RS-232 level. The EOE-W55RP20 and WIZ-IP20 pins are 3.3 V TTL.
• The WIZ-IP20's P13 (LINKLED) and P1 (ACTLED) are the link and activity LED signals driven directly by the Ethernet chip, and they are low when lit (GP10 and GP11 are high). The WIZ-IP20 has no DTR/DSR pins, so DTR/DSR flow control cannot be used on it.
• The AT port speed can be set from 9600 to 921600 bps.
• Flow control: none, RTS/CTS, DTR/DSR or XON/XOFF. To send binary data such as a certificate or firmware, the port must use 8 data bits and a flow control other than XON/XOFF.
• For power, operating temperature, dimensions and other electrical and mechanical specifications, see the module hardware datasheet.

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Quick Start

1. Connect the AT port at 115200 8N1, send AT and check that OK comes back.
2. Set the address. Choose DHCP or static with AT+NETMODE, then apply it with AT+SAVE.
3. Turn on BACnet. Set the mode and the Device instance with AT+BACMODE=BIP and AT+BACDEV, and do not forget AT+SAVE.
4. Check that the device appears in the workstation, then create objects and send values.

note

From the factory the module uses the static IP 192.168.11.2 and BACnet is off (AT+BACMODE? → +BACMODE:OFF,STOPPED). In this state the module does not answer Who-Is at all, so BACnet must be turned on before you look for the device from a workstation. It is the step most often missed on a first connection.

For example, publishing a temperature value over BACnet looks like this:

AT+BACMODE=BIP                                         turn on BACnet/IP (once)
AT+BOBJADD=AI,1,"Supply Temp",degrees-celsius          create an Analog Input object (once)
AT+SAVE                                                store the settings and objects
AT+BOBJVAL=AI,1,21.5                                   update the value

A workstation reading the Present_Value of analog-input,1 now gets 21.5. When the value changes, send AT+BOBJVAL again; the module reports the new value to every workstation that has subscribed to COV.

The full procedure is in the Getting Started Guide.

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Customization Services

WIZnet offers customization services for your specific needs. Based on the EOE-W55RP20_BACnet module, the following can be changed or added to suit your application:

• Changing the factory defaults
• Changing the MAC address
• Preloading the end-product manufacturer's identity (Vendor ID, company name and model name) and object set
• Adding protocols
• Adding functions

The customized firmware is programmed into the W55RP20 and delivered.

To request customization, fill in the customization service request form.