BACnet B-SS (Smart Sensor) - Go example

A minimal, read-only BACnet/IP device built on the CAS BACnet Stack, implementing the B-SS (BACnet Smart Sensor) standardized device profile in Go, via cgo bindings to the stack's native C library.

This is the fifth language port in a series that also has C++, C#, Node.js, Python and Rust editions, all implementing the same device/object model so the languages diff 1:1.

What is the B-SS (Smart Sensor) profile?

B-SS (ANSI/ASHRAE 135 Annex L.8, "Smart Sensor") is the standardized device profile for a simple, read-only sensing device: it presents one or more Input objects (Analog/Binary/Multi-State), answers ReadProperty for every required property, and is discoverable via Who-Is/I-Am and Who-Has/I-Have. It does not support WriteProperty, ReadPropertyMultiple, COV, alarms, or scheduling - those belong to richer profiles (B-AAC, B-ASC, ...) elsewhere in this series.

The device this example creates

Object	Instance	Name	Notes
Device	389001	Chipkin Example B-SS	vendor ID 389 (Chipkin), `--deviceID` configurable
Analog Input	1	Bronze	REAL, degrees Celsius, starts 21.5, nudged +/-1.1 via interactive commands
Binary Input	1	Emerald	starts inactive
Multi-State Input	1	Hot Pink	state 1 of 3 ("On"/"Off"/"Auto"), `State_Text` enabled
Network Port	1	Vermilion	BACnet/IP, IPv4 auto-discovered

See docs/objects.json for the full property-level breakdown and docs/PICS.md for the formal conformance statement.

What this example supports

BIBBs (BACnet Interoperability Building Blocks)

DS-RP-B - Data Sharing - ReadProperty - B
DM-DDB-B - Device Management - Dynamic Device Binding - B (Who-Is/I-Am)
DM-DOB-B - Device Management - Dynamic Object Binding - B (Who-Has/I-Have)

Services (executed / B-side)

SERVICE_READ_PROPERTY, SERVICE_WHO_IS, SERVICE_I_AM, SERVICE_WHO_HAS, SERVICE_I_HAVE. Nothing else is enabled - no WriteProperty, no ReadPropertyMultiple, no COV, no alarm/event service.

Object types

Device, Analog Input, Binary Input, Multi-State Input, Network Port. Every required property of every object is served; the Device's Description and the Multi-State Input's State_Text are the only optional properties this example turns on.

Requires the CAS BACnet Stack (licensed product)

This example links against the CAS BACnet Stack's native library (CASBACnetStack_x64_Release.dll on Windows, libCASBACnetStack_x64_Release.so on Linux), built from the submodules/cas-bacnet-stack submodule (branch 6.x, a licensed Chipkin product - see that submodule's own license). This repository ships no native binary in git history for anyone who has not already cloned this submodule with credentials; see "Build the native CAS BACnet Stack library" below.

What's in this repository

main.go                              CLI, device/object setup, run loop, interactive commands
go.mod

cas_bacnet_stack/                    the vendored + FIXED cgo adapter (see its own README.md)
  cas_bacnet_stack_adapter.go        cgo preamble, callback registration, Get*Property callbacks, thin stack wrappers
  cas_bacnet_stack_trampolines.c     the C-side callback trampolines (see file header for why this is a real .c file)
  README.md                          every fix made to the vendored adapter, and why

common/                              cgo-free shared plumbing (device state, transport, CLI helpers)
  constants.go                       BACnet enumeration values + this example's device/object constants
  device_state.go                    the device's mutable state (package-level, mutex-guarded)
  simple_udp.go                      application-owned, non-blocking UDP socket
  cas_example_helper.go              local IPv4 discovery, CLI arg parsing
  CHANGELOG.md

docs/
  objects.json                       machine-readable object/property model (ported from the C++/Rust editions)
  PICS.md                            BACnet Protocol Implementation Conformance Statement

lib/                                 the built native library lands here (gitignored except for a placeholder)
submodules/cas-bacnet-stack/         the CAS BACnet Stack, branch 6.x (submodule)

.github/workflows/release.yml        CI: build native lib + Go binary, smoke test, release on tag
TUTORIAL.md                          how to extend this example
CHANGELOG.md                         this example's own version history
AGENTS.md                            ground rules for an agent (or a careful human) touching this code
LICENSE                              CC0-1.0 (this example's own code; the submodule has its own license)

Prerequisites

Go 1.20+ (this repo was built and verified against go1.26.3; go.mod declares go 1.20 as the minimum - see cas_bacnet_stack/README.md for why that floor, matching the vendored adapter's own propertybufferhelper/go.mod precedent).
CGO_ENABLED=1 - this example is cgo-only; CGO_ENABLED=0 will not build it. Go turns this on by default when a C compiler is found on PATH, but CI sets it explicitly (see .github/workflows/release.yml).
A C compiler for cgo. On Windows this means MinGW-w64/gcc - not the MSVC toolchain that builds the native DLL itself. They are two separate compilers for two separate jobs: MSBuild/MSVC builds CASBACnetStack_x64_Release.dll from the submodule's C++ sources; cgo's gcc compiles this repo's own small C trampoline file and links against that already-built DLL. On Linux, any gcc/clang works for both jobs.
Git, for the submodule.

Build

1. Add the submodule

git submodule update --init --recursive

(Already wired via .gitmodules if you cloned this repository directly.)

2. Build the native CAS BACnet Stack library

Reuse, don't rebuild, when possible. A from-scratch MSVC build of the native library takes several minutes; if a sibling example in this series (the Rust or Python edition, for instance) has already built CASBACnetStack_x64_Release.dll at the same submodule commit this repository is pinned to, just copy that file into lib/ instead of rebuilding - git -C submodules/cas-bacnet-stack rev-parse HEAD from both repositories tells you whether the commits match.

Windows (MSBuild, if you do need to build it):

msbuild submodules\cas-bacnet-stack\projects\msvs\BuildCASBACnetStack.sln `
  /p:Configuration=ReleaseDll /p:Platform=x64 /p:PlatformToolset=v143
copy submodules\cas-bacnet-stack\<build output path>\CASBACnetStack_x64_Release.dll lib\

Linux (g++):

g++ -shared -fPIC -o lib/libCASBACnetStack_x64_Release.so \
  submodules/cas-bacnet-stack/source/*.cpp -I submodules/cas-bacnet-stack/source

Why only a Release build

Same reasoning as every sibling edition of this example: this repository only ever builds/ships the Release configuration of the native library. There is no reason for a tutorial example to link a Debug build, and the vendored adapter skeleton's original #cgo LDFLAGS: ... -lCASBACnetStack_x64_Debug was one of the bugs this fork fixes - see cas_bacnet_stack/README.md fix #5.

3. Build the Go binary

CGO_ENABLED=1 go build -o bacnet-b-ss-go .

(On Windows PowerShell: $env:CGO_ENABLED=1; go build -o bacnet-b-ss-go.exe .)

4. Put the native library where the built binary can find it

cgo links CASBACnetStack_x64_Release at build time via #cgo LDFLAGS pointing at lib/ (see cas_bacnet_stack/cas_bacnet_stack_adapter.go), but the OS's dynamic loader still needs to find the DLL/so at run time. Copy it next to the built executable:

cp lib/CASBACnetStack_x64_Release.dll .        # Windows, next to bacnet-b-ss-go.exe
cp lib/libCASBACnetStack_x64_Release.so .      # Linux, next to bacnet-b-ss-go

If the library cannot be found, the OS loader fails before main() runs, with its own native error (e.g. Windows: "The code execution cannot proceed because CASBACnetStack_x64_Release.dll was not found").

Run

./bacnet-b-ss-go --port 47808 --deviceID 389001

Command-line options

Flag	Default	Meaning
`--port`	47808	BACnet/IP UDP port
`--deviceID`	389001	BACnet Device instance (0..4194302)
`--version`	-	print version and exit
`--help`	-	print flag usage and exit (Go's `flag` package default)

Interactive commands

Type a command and press Enter (see "Interactive commands are a simplification" in main.go / TUTORIAL.md for why this is line-buffered, not raw single-keypress, input):

Command	Effect
`h`, `help`	show help
`q`, `quit`	stop the device
`up`, `u`	nudge Analog Input 1 (Bronze) up by 1.1 C
`down`, `d`	nudge Analog Input 1 (Bronze) down by 1.1 C

Ctrl+C also stops the device cleanly.

Verify

From another machine (or the same one) on the same subnet, use a BACnet explorer (e.g. YABE, VTS, or Chipkin's own BACnet Explorer) to send a Who-Is and confirm Device 389001 ("Chipkin Example B-SS") answers with an I-Am, then browse its four objects and read their properties.

How the Go binding differs from the C++/C#/Python/Rust editions

cgo, not P/Invoke/ctypes/dlopen/libloading. The native library is linked at build time (#cgo LDFLAGS), not resolved dynamically at run time the way C#'s P/Invoke, Python's ctypes, or the Rust edition's libloading::Library do. The trade-off: no "library not found" runtime panic to catch (the OS loader fails before main() even starts - see "Put the native library where the built binary can find it" above), but a rebuild is required if you ever want to point at a different native library file name.
Package-level state, not closures - same root cause as Rust, different mechanism. Go's cgo //export functions must be top-level, non-method, non-closure functions - a hard cgo rule, not a style choice. So exactly like the Rust edition's plain extern "C" fn items, this edition's callbacks read/write common's package-level DeviceState through a mutex (common.WithState) rather than capturing a main()-local variable. See common/device_state.go's doc comment.
A real vendored, fixed C adapter file - the only edition in this series with one. The C++ edition talks to the stack's C++ classes directly; C#/Python/Rust vendor pure FFI binding layers (function signatures only) that never shipped broken. The Go adapter is different: submodules/cas-bacnet-stack/adapters/golang/CASBACnetStackAdapter.go is a real, hand-maintained cgo skeleton that had genuinely stopped compiling against the current 6.x header (renamed transport callbacks, a wrong time_t vs CASBACnetTime type, and only 2 of 6 needed Get*Property callbacks wired). Fixing it - in this repository's own vendored copy only, never in submodules/ - is real "fix the language adapter" work; see cas_bacnet_stack/README.md for the complete list.
A dependency-free stdlib transport, like Rust's. No transport helper ships in adapters/golang/ any more than it does in adapters/rust/; common/simple_udp.go is written from scratch against net.ListenUDP/net.UDPConn, matching simple_udp.rs's shape and responsibilities.
Line-buffered interactive commands, like Rust's. Go's standard library has no portable non-blocking single-keypress read either (that needs golang.org/x/term or similar) - this edition made the same dependency-free choice the Rust edition did, for the same reason.

The BACnet profile example series

The CAS BACnet Stack supports every standardized device profile in ASHRAE 135-2024 Annex L, and there is one example repository per profile. Pick the profile your device claims, then the language you build in. "Ask" means the example hasn't been built yet for that language - contact Chipkin if you need one.

Controllers (Annex L.4)

Profile	C++	Node.js	C#	Rust	Python	Go
B-SS Smart Sensor	B-SS-CPP	B-SS-Node	B-SS-CS	B-SS-Rust	B-SS-Python	B-SS-Go
B-SA Smart Actuator	B-SA-CPP	Ask	Ask	Ask	Ask	Ask
B-ASC Application Specific Controller	B-ASC-CPP	B-ASC-Node	Ask	Ask	Ask	Ask
B-AAC Advanced Application Controller	B-AAC-CPP	Ask	Ask	Ask	Ask	Ask
B-BC Building Controller	B-BC-CPP	Ask	Ask	Ask	Ask	Ask

Life safety controllers (Annex L.5)

Profile	C++	Node.js	C#	Rust	Python	Go
B-LSC Life Safety Controller	B-LSC-CPP 🚧	Ask	Ask	Ask	Ask	Ask
B-ALSC Advanced Life Safety Controller	B-ALSC-CPP	Ask	Ask	Ask	Ask	Ask

Access control controllers (Annex L.6)

Profile	C++	Node.js	C#	Rust	Python	Go
B-ACC Access Control Controller	B-ACC-CPP	Ask	Ask	Ask	Ask	Ask
B-AACC Advanced Access Control Controller	B-AACC-CPP	Ask	Ask	Ask	Ask	Ask

Lighting controllers (Annex L.11)

Profile	C++	Node.js	C#	Rust	Python	Go
B-LD Lighting Device	B-LD-CPP	Ask	Ask	Ask	Ask	Ask
B-LS Lighting Supervisor	B-LS-CPP	Ask	Ask	Ask	Ask	Ask

Elevator controllers (Annex L.13)

Profile	C++	Node.js	C#	Rust	Python	Go
B-EM Elevator Monitor	B-EM-CPP	Ask	Ask	Ask	Ask	Ask
B-EC Elevator Controller	B-EC-CPP	Ask	Ask	Ask	Ask	Ask
B-AEC Advanced Elevator Controller	B-AEC-CPP	Ask	Ask	Ask	Ask	Ask

Authentication and authorization (Annex L.14)

Profile	C++	Node.js	C#	Rust	Python	Go
B-AS Authorization Server	B-AS-CPP	Ask	Ask	Ask	Ask	Ask

Miscellaneous (Annex L.7, combinable with any one family)

Profile	C++	Node.js	C#	Rust	Python	Go
B-BBMD Broadcast Management Device	B-BBMD-CPP	Ask	Ask	Ask	Ask	Ask
B-ACDC Access Control Door Controller	B-ACDC-CPP	Ask	Ask	Ask	Ask	Ask
B-ACCR Access Control Credential Reader	B-ACCR-CPP	Ask	Ask	Ask	Ask	Ask
B-RTR Router	B-RTR-CPP	Ask	Ask	Ask	Ask	Ask
B-GW Gateway	B-GW-CPP	Ask	Ask	Ask	Ask	Ask
B-DAP Device Address Proxy	B-DAP-CPP	Ask	Ask	Ask	Ask	Ask
B-SCHUB BACnet/SC Hub	B-SCHUB-CPP	Ask	Ask	Ask	Ask	Ask
B-GENERAL General device (Annex L.8)	(satisfied by every example above)	—	—	—	—	—

Operator interfaces and workstations (Annex L.1–L.3, L.9–L.10, L.12)

Client-side profiles.

Profile	C++	Node.js	C#	Rust	Python	Go
B-OD Operator Display	B-OD-CPP	Ask	Ask	Ask	Ask	Ask
B-OWS Operator Workstation	planned	—	—	—	—	—
B-AWS Advanced Operator Workstation	planned	—	—	—	—	—
B-XAWS Extended Advanced Operator Workstation	planned	—	—	—	—	—
B-LSAP Life Safety Annunciator Panel	planned	—	—	—	—	—
B-LSWS Life Safety Workstation	planned	—	—	—	—	—
B-ALSWS Advanced Life Safety Workstation	planned	—	—	—	—	—
B-ACSD Access Control Security Display	planned	—	—	—	—	—
B-ACWS Access Control Workstation	planned	—	—	—	—	—
B-AACWS Advanced Access Control Workstation	planned	—	—	—	—	—
B-LOD Lighting Operator Display	planned	—	—	—	—	—
B-ALWS Advanced Lighting Workstation	planned	—	—	—	—	—
B-LCS Lighting Control Station	planned	—	—	—	—	—
B-ALCS Advanced Lighting Control Station	planned	—	—	—	—	—
B-ED Elevator Display	planned	—	—	—	—	—
B-EWS Elevator Workstation	planned	—	—	—	—	—
B-AEWS Advanced Elevator Workstation	planned	—	—	—	—	—

🚧 = in progress. "Ask" = not yet built for that language; contact Chipkin if you need it. Profile definitions: ANSI/ASHRAE 135-2024 Annex L. BIBB definitions: Annex K. Get the stack: https://store.chipkin.com/services/stacks/bacnet-stack.

References

ANSI/ASHRAE Standard 135-2024, Annex A (PICS template), Annex K (BIBBs), Annex L (device profiles), Clause 12 (object types).
CAS BACnet Stack documentation.
TUTORIAL.md - how to extend this example.
docs/PICS.md - the formal conformance statement.
cas_bacnet_stack/README.md - the vendored adapter fixes.

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BACnet B-SS (Smart Sensor) - Go example

What is the B-SS (Smart Sensor) profile?

The device this example creates

What this example supports

BIBBs (BACnet Interoperability Building Blocks)

Services (executed / B-side)

Object types

Requires the CAS BACnet Stack (licensed product)

What's in this repository

Prerequisites

Build

1. Add the submodule

2. Build the native CAS BACnet Stack library

Why only a Release build

3. Build the Go binary

4. Put the native library where the built binary can find it

Run

Command-line options

Interactive commands

Verify

How the Go binding differs from the C++/C#/Python/Rust editions

The BACnet profile example series

Controllers (Annex L.4)

Life safety controllers (Annex L.5)

Access control controllers (Annex L.6)

Lighting controllers (Annex L.11)

Elevator controllers (Annex L.13)

Authentication and authorization (Annex L.14)

Miscellaneous (Annex L.7, combinable with any one family)

Operator interfaces and workstations (Annex L.1–L.3, L.9–L.10, L.12)

References

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Name		Name	Last commit message	Last commit date
.github/workflows		.github/workflows
cas_bacnet_stack		cas_bacnet_stack
common		common
docs		docs
lib		lib
submodules		submodules
.gitignore		.gitignore
.gitmodules		.gitmodules
AGENTS.md		AGENTS.md
CHANGELOG.md		CHANGELOG.md
LICENSE		LICENSE
README.md		README.md
TUTORIAL.md		TUTORIAL.md
go.mod		go.mod
main.go		main.go

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BACnet B-SS (Smart Sensor) - Go example

What is the B-SS (Smart Sensor) profile?

The device this example creates

What this example supports

BIBBs (BACnet Interoperability Building Blocks)

Services (executed / B-side)

Object types

Requires the CAS BACnet Stack (licensed product)

What's in this repository

Prerequisites

Build

1. Add the submodule

2. Build the native CAS BACnet Stack library

Why only a Release build

3. Build the Go binary

4. Put the native library where the built binary can find it

Run

Command-line options

Interactive commands

Verify

How the Go binding differs from the C++/C#/Python/Rust editions

The BACnet profile example series

Controllers (Annex L.4)

Life safety controllers (Annex L.5)

Access control controllers (Annex L.6)

Lighting controllers (Annex L.11)

Elevator controllers (Annex L.13)

Authentication and authorization (Annex L.14)

Miscellaneous (Annex L.7, combinable with any one family)

Operator interfaces and workstations (Annex L.1–L.3, L.9–L.10, L.12)

References

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