Add phased implementation roadmap

docs/implementation-roadmap.md

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+# Implementation Roadmap
+
+## Purpose
+
+This document defines the planned implementation order for the Xterra Overland Power & Monitoring Dashboard.
+
+The goal is to build the system incrementally, validating hardware and software at each stage before adding additional complexity.
+
+---
+
+# Current Status
+
+## Complete
+
+* Project architecture defined
+* Hardware architecture defined
+* UART protocol defined
+* Pico architecture defined
+* UI wireframes defined
+* ESP32 firmware compiles
+* Simulator exists and functions
+
+## In Progress
+
+* ESP32 controller firmware
+* Communication protocol implementation
+
+## Not Started
+
+* Pico firmware
+* Display integration
+* Touch integration
+* Buzzer integration
+* End-to-end communications
+
+---
+
+# Milestone 1: ESP32 Hardware Bring-Up
+
+## Goal
+
+Verify cargo-controller hardware.
+
+## Tasks
+
+* Flash ESP32 firmware
+* Verify boot process
+* Verify AP mode
+* Verify HTTP API
+* Verify relay outputs
+* Verify DS18B20 framework
+* Verify UART initialization
+
+## Success Criteria
+
+* ESP32 boots reliably
+* Relay outputs function correctly
+* Status API responds correctly
+* No crashes or watchdog resets
+
+---
+
+# Milestone 2: Pico Hardware Bring-Up
+
+## Goal
+
+Verify dashboard hardware.
+
+## Tasks
+
+* Verify Pico 2 W operation
+* Verify ST7796S display
+* Verify FT6336U touch controller
+* Verify buzzer operation
+
+## Success Criteria
+
+* Display initializes reliably
+* Touch events are detected
+* Buzzer can be activated
+
+---
+
+# Milestone 3: UART Communications
+
+## Goal
+
+Establish communications between Pico and ESP32.
+
+## Tasks
+
+* Wire UART over CAT5
+* Implement status requests
+* Implement status responses
+* Implement relay commands
+* Implement error handling
+* Implement communication timeout detection
+
+## Success Criteria
+
+* Pico receives live status
+* Pico can control relays
+* Communication loss is detected
+
+---
+
+# Milestone 4: Dashboard UI Foundation
+
+## Goal
+
+Render live data on the touchscreen.
+
+## Tasks
+
+* Create screen manager
+* Create app state
+* Create dashboard screen
+* Create navigation bar
+* Create communication status indicators
+
+## Success Criteria
+
+* Live battery data displayed
+* Live temperature data displayed
+* Navigation functional
+
+---
+
+# Milestone 5: Detailed Screens
+
+## Goal
+
+Implement all planned screens.
+
+## Tasks
+
+### Battery Screen
+
+* SOC
+* Voltage
+* Current
+* Runtime
+* Temperature
+
+### Temperature Screen
+
+* Fridge Zone 1
+* Fridge Zone 2
+* Rear Seat
+* Outside Air
+
+### Power Screen
+
+* Starlink control
+* Fridge control
+
+### System Screen
+
+* Communication status
+* Sensor status
+* Firmware information
+
+## Success Criteria
+
+* All screens functional
+* Navigation stable
+* Live updates working
+
+---
+
+# Milestone 6: Alarm System
+
+## Goal
+
+Implement alerting and warning system.
+
+## Tasks
+
+* Alarm manager
+* Alarm overlay
+* Communication alarms
+* Battery alarms
+* Temperature alarms
+* Sensor fault alarms
+* Buzzer manager
+
+## Success Criteria
+
+* Alarms trigger correctly
+* Alarm overlay displays correctly
+* Buzzer alerts function correctly
+
+---
+
+# Milestone 7: DS18B20 Integration
+
+## Goal
+
+Implement all production sensors.
+
+## Sensors
+
+### Fridge Zone 1
+
+Monitor refrigerator compartment.
+
+### Fridge Zone 2
+
+Monitor freezer compartment.
+
+### Rear Seat Area
+
+Monitor passenger compartment.
+
+### Outside Air
+
+Monitor ambient exterior temperature.
+
+## Success Criteria
+
+* All sensors report correctly
+* Sensor failures are detected
+
+---
+
+# Milestone 8: JBD/Xiaoxiang BMS Integration
+
+## Goal
+
+Replace simulated battery data with live battery data.
+
+## Tasks
+
+* BLE communication
+* Battery status retrieval
+* Runtime calculations
+* Health monitoring
+
+## Success Criteria
+
+* Live battery data displayed
+* No simulated battery values required
+
+---
+
+# Milestone 9: Vehicle Integration
+
+## Goal
+
+Add vehicle-specific information.
+
+## Potential Features
+
+* Ignition state
+* OBD-II integration
+* CAN bus integration
+* Engine information
+* Fuel information
+
+## Status
+
+Future planning only.
+
+---
+
+# Milestone 10: Future Expansion
+
+## Potential Features
+
+* Additional relays
+* Inverter control
+* Lighting control
+* Starlink diagnostics
+* GPS integration
+* Home Assistant integration
+
+## Status
+
+Future planning only.
+
+---
+
+# Explicitly Not Planned
+
+The following items are currently out of scope:
+
+* Cloud connectivity
+* Internet dependency
+* User accounts
+* Persistent logging
+* Historical graphing
+* Subscription services
+
+The system should remain fully functional offline.