docs: Add BACnet conversation log

- Create a new log file and content files detailing the
  discussion about BACnet and Modbus protocols.

Makefile

@@ -15,7 +15,11 @@ goimports:
 
 test:
 	# GO111MODULE=off go run format_rich_log.go log/2025-08-20-rich.text
-	GO111MODULE=off go run format_rich_log.go log/2025-08-20-full.text
+	# GO111MODULE=off go run format_rich_log.go log/2025-08-20-full.text
+	GO111MODULE=off go run format_rich_log.go log/2025-08-20-final.text
 
 gemini-config:
 	cp ~/.gemini/GEMINI.md .
+
+gemini-go:
+	~/go/bin/gemini playback

log/BACnet.text

@@ -0,0 +1,12 @@
+uuid: "bacnet-log-01"
+version: "v0.0.3 go.wit.com/lib/protobuf/chatpb"
+Chats: {
+  from: USER
+  ctime: { seconds: 1724166000 }
+  content_file: "content/bacnet_q1.content"
+}
+Chats: {
+  from: GEMINI
+  ctime: { seconds: 1724166060 }
+  content_file: "content/bacnet_a1.content"
+}

log/content/bacnet_a1.content

@@ -0,0 +1,20 @@
+You've described the situation perfectly. The protocol you're thinking of for HVAC and industrial controls is almost certainly **BACnet** or **Modbus**.
+
+Both are foundational protocols in building automation and industrial control, and they share the same conceptual space as CAN bus does for vehicles.
+
+First, to clarify your other point: **CAN bus** (Controller Area Network) is exactly what it's called. It's a robust vehicle bus standard designed to allow microcontrollers and devices to communicate with each other's applications without a host computer.
+
+Here is a breakdown of the industrial/HVAC equivalents:
+
+| Protocol | Primary Use | Physical Layer | Key Concept (How it's like CAN bus) |
+| :--- | :--- | :--- | :--- |
+| **BACnet** | **Modern HVAC & Building Automation** | Runs on many layers, but commonly **RS-485** (a 2-wire bus, like CAN) or Ethernet (BACnet/IP). | This is the dominant, open standard for complex building control (chillers, air handlers, lighting, security). It allows devices from different manufacturers to interoperate in a single system. |
+| **Modbus** | **Industrial Controls & Simple HVAC** | Also commonly runs on **RS-485** (Modbus RTU) or Ethernet (Modbus TCP). | This is the de facto standard for industrial devices. It's simpler than BACnet and is a master-slave protocol (one device polls, others respond), but it serves the same purpose of connecting sensors, drives, and controllers on a shared network. |
+| **LonWorks** | Building, Home, and Industrial Automation | Twisted Pair (Free Topology) | A strong competitor to BACnet. It's a peer-to-peer protocol, which is conceptually very similar to CAN's multi-master design, where any device can initiate communication. |
+
+### Which one are you thinking of?
+
+*   If you're thinking about a modern, large commercial building's entire automation system, the answer is **BACnet**.
+*   If you're thinking about the most common, simple, and widespread protocol for connecting industrial sensors, VFDs (Variable Frequency Drives), and basic controllers, the answer is **Modbus**.
+
+Given the direct comparison to CAN bus as a system-wide network, **BACnet** is the most likely protocol you're trying to remember for the HVAC world.

log/content/bacnet_q1.content

@@ -0,0 +1 @@
+there is a protocol used in HVAC and instustrial controls but I forgot what it is called. It is similar in concept to what the automotive industry uses called "canBUS" or "CAN BUS" (I'm not sure what that is called either).