bacnet_stack/ports/esp32/README.md

ESP32 Port

Date: 2026-04-04 Author: Kato Gangstad

This folder contains the ESP32 BACnet port built with PlatformIO. It targets multiple ESP32-family boards and covers BACnet MS/TP, BACnet/IP, and BACnet Gateway (based on apps/gateway2) profiles. It is based on the current lwIP port and Pico port patterns in this repository.

Current Scope

• BACnet MS/TP transport for ESP32 boards with RS485
• BACnet/IP transport for compact WiFi and Ethernet ESP32 targets
• BACnet routing between BACnet/IP and BACnet MS/TP

Port Identity

It is the ESP32 BACnet port for the current PlatformIO-based targets in this repository.

Supported Board Profiles

The current board coverage includes:

• Seeed Studio XIAO ESP32C3 for ultra-compact BACnet/IP
• M5StamPLC for BACnet MS/TP and BACnet router builds
• Olimex ESP32-POE for BACnet/IP

The upstream BACnet stack has a broad source set and multiple app profiles. This port selects the ESP32-specific transport, board, and application wiring needed for the environments documented below.

Files

• src/main.cpp: Application loop, BACnet object table, and PLC I/O sync
• src/mstimer_init.c: millisecond timer hook used by mstimer
• src/rs485.c: ESP32 RS485 low-level driver for MS/TP
• src/dlenv.c: MS/TP datalink environment setup and port wiring
• src/bip_socket.cpp: BACnet/IP UDP socket bridge for WiFi and Ethernet targets
• extra_script.py: Injects BACnet core/basic sources into the PlatformIO build

Build Notes

1. Open this folder as a PlatformIO project root, or run PlatformIO with this folder as cwd.
2. Start with the environment that matches your board and transport profile.
3. The platformio.ini file defines all tested board environments for this port.
4. Ensure PlatformIO CLI is available in your shell (pio --version).
5. Build with pio run -e <environment-name>.

Tested Environments

The following PlatformIO environments have been built and uploaded successfully:

• xiao-esp32c3-wifi-bip on Seeed Studio XIAO ESP32C3
• m5stamplc-mstp on M5StamPLC
• m5stamplc-gateway-bip-mstp on M5StamPLC
• esp32-poe-wifi-bip on Olimex ESP32-POE

Validation Tools

Interoperability and functional verification have been tested with:

• YABE
• Honeywell Eaglehawk 4.15
• Tridium Niagara 4.15

Board Pictures

The following board photos document the hardware used for the tested environments.

Seeed Studio XIAO ESP32C3

Used for:

• xiao-esp32c3-wifi-bip

Why this board stands out:

• Extremely compact form factor for a BACnet/IP target
• Physical size: 21 x 17.8 mm
• Strong candidate for one of the smallest BACnet/IP device ever !

Hardware summary:

• MCU: ESP32-C3
• CPU type: 32-bit single-core RISC-V
• CPU clock: 160 MHz
• RAM: 320 KB
• Flash: 4 MB

M5StamPLC

• BACnet server object model with Device + Binary Input + Binary Output objects
• Runtime mapping:
  • BI 0..7 <- PLC inputs 1..8
  • BO 0..3 -> PLC relays 1..4
• RS485 pin mapping aligned with the M5StamPLC hardware profile:
  • TX: GPIO0
  • RX: GPIO39
  • DIR: GPIO46

Used for:

• m5stamplc-mstp
• m5stamplc-bip
• m5stamplc-gateway-bip-mstp
• soon to come m5stamplc-poe-bip

Hardware summary:

• MCU: ESP32-S3
• CPU clock: 240 MHz
• RAM: 320 KB
• Flash: 8 MB

Olimex ESP32-POE

Used for:

• esp32-poe-wifi-bip
• esp32-poe-eth-bip

Hardware summary:

• MCU: ESP32
• CPU clock: 240 MHz
• RAM: 320 KB
• Flash: 4 MB