# Phase 1 Development Plan: py-dvt-ate MVP

| Document ID | DEV-001 |
|-------------|---------|
| Version | 2.0.0 |
| Status | Approved |
| Author | Kai Chappell |
| Created | 2025-12-01 |
| Last Updated | 2025-12-01 |

---

## Purpose

This document defines **when** to build each component of py-dvt-ate Phase 1. It provides an iterative sprint breakdown with atomic tasks optimised for incremental development.

For **what** the system must do, see `01_requirements.md`.
For **how** to implement the system, see `02_technical_specification.md`.
For **why** decisions were made, see `03_architecture_decisions.md`.

---

## Design Principles

1. **Small, Focused Commits** - Each task = 1 commit, ~50-150 lines changed
2. **Stubs First** - Define interfaces/types before implementation
3. **Vertical Slice First** - Get something visual early, then build infrastructure
4. **Minimal Context** - Each task completable with knowledge of 1-3 files
5. **Test Alongside** - Write tests immediately after implementation
6. **Iterative Refinement** - Get something working, then improve

---

## Sprint Structure

Each sprint is ~1-2 days of work, producing demonstrable progress.

**Vertical Slice Strategy:**
- Sprints 1-3: Foundation + Physics Engine (the core simulation)
- Sprint 4: Dashboard (see the physics working!)
- Sprints 5-11: Infrastructure/Plumbing (SCPI, TCP, HAL)
- Sprints 12-17: Test Framework, CLI, Polish

---

## Sprint 1: Project Foundation

**Goal:** Establish project structure and build system.

### Task 1.1: Create pyproject.toml
- Create minimal pyproject.toml with project metadata
- Package name: `py_dvt_ate`
- Include only core dependencies initially
- **Commit:** "Add pyproject.toml with core dependencies"

### Task 1.2: Create directory structure (empty)
- Create src/py_dvt_ate/ with __init__.py and py.typed
- Create empty subpackage directories with __init__.py
- Create tests/ directory structure
- Create config/ directory
- **Commit:** "Add package directory structure"

### Task 1.3: Add development tooling config
- Add ruff configuration to pyproject.toml
- Add mypy configuration to pyproject.toml
- Add pytest configuration to pyproject.toml
- **Commit:** "Configure development tooling (ruff, mypy, pytest)"

### Task 1.4: Create basic CLI entry point
- Create src/py_dvt_ate/cli/__init__.py
- Create src/py_dvt_ate/cli/main.py with Typer app stub
- Add version command only
- **Commit:** "Add CLI entry point with version command"

---

## Sprint 2: Physics Engine Core (Stubs)

**Goal:** Define physics interfaces and data structures.

### Task 2.1: Define thermal state dataclasses
- Create src/py_dvt_ate/physics/__init__.py
- Create src/py_dvt_ate/physics/models.py
- Define ThermalState (frozen dataclass)
- Define ElectricalState (frozen dataclass)
- **Commit:** "Add physics state dataclasses"

### Task 2.2: Define DUT base protocol
- Create src/py_dvt_ate/physics/dut/__init__.py
- Create src/py_dvt_ate/physics/dut/base.py
- Define DUTModel Protocol with method signatures
- **Commit:** "Add DUT model protocol"

### Task 2.3: Create physics engine stub
- Create src/py_dvt_ate/physics/engine.py
- Define PhysicsEngine class with stub methods
- Methods return placeholder values
- **Commit:** "Add physics engine stub"

### Task 2.4: Add physics unit tests (for stubs)
- Create tests/unit/test_physics_models.py
- Test dataclass creation and immutability
- **Commit:** "Add physics model unit tests"

---

## Sprint 3: Physics Engine Implementation

**Goal:** Implement working physics simulation.

### Task 3.1: Implement thermal calculations
- Create src/py_dvt_ate/physics/thermal.py
- Implement first-order thermal response calculations
- Pure functions, no state
- **Commit:** "Implement thermal calculation functions"

### Task 3.2: Implement LDO DUT model
- Create src/py_dvt_ate/physics/dut/ldo.py
- Implement LDOModel class
- Temperature-dependent Vout, Iq calculations
- Power dissipation calculation
- **Commit:** "Implement LDO DUT model"

### Task 3.3: Implement physics engine step()
- Update engine.py with working step() method
- Integrate thermal calculations
- Integrate DUT model
- **Commit:** "Implement physics engine stepping"

### Task 3.4: Add physics integration tests
- Create tests/unit/test_physics_engine.py
- Test thermal settling behaviour
- Test self-heating effects
- **Commit:** "Add physics engine tests"

---

## Sprint 4: Streamlit Dashboard (Early Visual!)

**Goal:** Visualise physics engine directly - see something working!

### Task 4.1: Create dashboard app skeleton
- Create src/py_dvt_ate/dashboard/__init__.py
- Create src/py_dvt_ate/dashboard/app.py
- Basic Streamlit page with title
- **Commit:** "Add Streamlit dashboard skeleton"

### Task 4.2: Add physics visualisation panel
- Create direct connection to PhysicsEngine (no HAL yet)
- Display chamber temperature, DUT temperature
- Real-time updating chart
- **Commit:** "Add physics visualisation panel"

### Task 4.3: Add interactive controls
- Temperature setpoint slider
- Input voltage control
- Load current control
- Start/Stop simulation button
- **Commit:** "Add interactive physics controls"

### Task 4.4: Add self-heating demonstration
- Show junction temperature vs case temperature
- Demonstrate thermal coupling visually
- **Commit:** "Add self-heating visualisation"

**Milestone:** Working "Virtual Lab Bench" toy to play with!

---

## Sprint 5: SCPI Foundation

**Goal:** Create SCPI parsing infrastructure.

### Task 5.1: Define SCPI command dataclass
- Create src/py_dvt_ate/instruments/__init__.py
- Create src/py_dvt_ate/instruments/scpi_parser.py
- Define SCPICommand dataclass
- **Commit:** "Add SCPI command dataclass"

### Task 5.2: Implement SCPI parser
- Implement SCPIParser.parse() method
- Handle queries, commands with arguments
- Handle IEEE 488.2 common commands (*IDN?, *RST)
- **Commit:** "Implement SCPI parser"

### Task 5.3: Add SCPI parser tests
- Create tests/unit/test_scpi_parser.py
- Test various command formats
- Test edge cases
- **Commit:** "Add SCPI parser tests"

---

## Sprint 6: Instrument Base & Thermal Chamber Simulator

**Goal:** Create first virtual instrument.

### Task 6.1: Define instrument base class
- Create src/py_dvt_ate/instruments/base.py
- Define BaseInstrument with common functionality
- Command dispatch mechanism
- **Commit:** "Add base instrument class"

### Task 6.2: Create thermal chamber simulator stub
- Create src/py_dvt_ate/instruments/thermal_chamber.py
- Define ThermalChamberSim class
- Stub SCPI command handlers
- **Commit:** "Add thermal chamber simulator stub"

### Task 6.3: Implement thermal chamber commands
- Implement TEMP:SETPOINT, TEMP:ACTUAL?, TEMP:STAB?
- Connect to physics engine reference
- **Commit:** "Implement thermal chamber SCPI commands"

### Task 6.4: Add thermal chamber tests
- Create tests/unit/test_thermal_chamber.py
- Test SCPI command responses
- **Commit:** "Add thermal chamber simulator tests"

---

## Sprint 7: Power Supply & DMM Simulators

**Goal:** Complete instrument simulators.

### Task 7.1: Create power supply simulator
- Create src/py_dvt_ate/instruments/power_supply.py
- Implement PSU SCPI commands
- VOLT, CURR, OUTP, MEAS commands
- **Commit:** "Add power supply simulator"

### Task 7.2: Add power supply tests
- Create tests/unit/test_power_supply.py
- **Commit:** "Add power supply simulator tests"

### Task 7.3: Create DMM simulator
- Create src/py_dvt_ate/instruments/multimeter.py
- Implement DMM SCPI commands
- MEAS:VOLT:DC?, CONF commands
- **Commit:** "Add multimeter simulator"

### Task 7.4: Add DMM tests
- Create tests/unit/test_multimeter.py
- **Commit:** "Add multimeter simulator tests"

---

## Sprint 8: TCP Server

**Goal:** Expose instruments over network.

### Task 8.1: Create async TCP server foundation
- Create src/py_dvt_ate/server/__init__.py
- Create src/py_dvt_ate/server/tcp_server.py
- Define InstrumentServer class with asyncio
- **Commit:** "Add async TCP server foundation"

### Task 8.2: Implement client connection handling
- Handle multiple concurrent connections
- Line-based SCPI protocol (newline terminated)
- **Commit:** "Implement TCP client handling"

### Task 8.3: Create server main entry point
- Create src/py_dvt_ate/server/main.py
- Wire up physics engine and instruments
- Add CLI command to start server
- **Commit:** "Add simulation server entry point"

### Task 8.4: Add server integration tests
- Create tests/integration/test_tcp_server.py
- Test connection and basic commands
- **Commit:** "Add TCP server integration tests"

---

## Sprint 9: Transport Layer (Client Side)

**Goal:** Create client-side communication.

### Task 9.1: Define transport protocol
- Create src/py_dvt_ate/transport/__init__.py
- Create src/py_dvt_ate/transport/base.py
- Define Transport Protocol class
- **Commit:** "Add transport protocol definition"

### Task 9.2: Implement TCP transport
- Create src/py_dvt_ate/transport/tcp.py
- Implement TCPTransport class
- connect(), write(), read(), query() methods
- **Commit:** "Implement TCP transport"

### Task 9.3: Add transport tests
- Create tests/unit/test_transport.py
- Test with mock socket
- **Commit:** "Add transport layer tests"

---

## Sprint 10: SCPI Drivers

**Goal:** Create instrument drivers using transport.

### Task 10.1: Define driver base class
- Create src/py_dvt_ate/drivers/__init__.py
- Create src/py_dvt_ate/drivers/base.py
- Define BaseDriver with transport dependency
- **Commit:** "Add driver base class"

### Task 10.2: Implement thermal chamber driver
- Create src/py_dvt_ate/drivers/thermal_chamber.py
- Methods map to SCPI commands
- **Commit:** "Add thermal chamber driver"

### Task 10.3: Implement PSU and DMM drivers
- Create src/py_dvt_ate/drivers/power_supply.py
- Create src/py_dvt_ate/drivers/multimeter.py
- **Commit:** "Add PSU and DMM drivers"

### Task 10.4: Add driver tests
- Create tests/unit/test_drivers.py
- Test command formatting
- **Commit:** "Add driver unit tests"

---

## Sprint 11: Hardware Abstraction Layer

**Goal:** Create HAL interfaces and implementations.

### Task 11.1: Define HAL protocols
- Create src/py_dvt_ate/hal/__init__.py
- Create src/py_dvt_ate/hal/interfaces.py
- Define IThermalChamber, IPowerSupply, IMultimeter
- **Commit:** "Add HAL protocol definitions"

### Task 11.2: Implement HAL wrappers
- Create src/py_dvt_ate/hal/impl/__init__.py
- Create HAL implementation classes
- Wrap drivers with HAL interface
- **Commit:** "Add HAL implementations"

### Task 11.3: Create instrument factory
- Create src/py_dvt_ate/hal/factory.py
- InstrumentSet dataclass
- InstrumentFactory.create() method
- **Commit:** "Add instrument factory"

### Task 11.4: Add HAL tests
- Create tests/unit/test_hal.py
- Test factory creates correct types
- **Commit:** "Add HAL unit tests"

---

## Sprint 12: Configuration System

**Goal:** YAML-based configuration.

### Task 12.1: Define config models
- Create src/py_dvt_ate/config/__init__.py
- Create src/py_dvt_ate/config/models.py
- Pydantic models for all config sections
- **Commit:** "Add configuration Pydantic models"

### Task 12.2: Implement config loader
- Create src/py_dvt_ate/config/loader.py
- Load YAML, validate with Pydantic
- Environment variable overrides
- **Commit:** "Implement configuration loader"

### Task 12.3: Create default config file
- Create config/default.yaml
- Document all options
- **Commit:** "Add default configuration file"

### Task 12.4: Add config tests
- Create tests/unit/test_config.py
- **Commit:** "Add configuration tests"

---

## Sprint 13: Data Persistence

**Goal:** Store test results.

### Task 13.1: Define data models
- Create src/py_dvt_ate/data/__init__.py
- Create src/py_dvt_ate/data/models.py
- TestRun, TestResult, Measurement dataclasses
- **Commit:** "Add data persistence models"

### Task 13.2: Create SQLite repository
- Create src/py_dvt_ate/data/repository.py
- Implement test run and result storage
- **Commit:** "Implement SQLite repository"

### Task 13.3: Add Parquet measurement storage
- Extend repository for Parquet files
- Batch measurement writing
- **Commit:** "Add Parquet measurement storage"

### Task 13.4: Add data persistence tests
- Create tests/unit/test_repository.py
- **Commit:** "Add data persistence tests"

---

## Sprint 14: Test Executive Framework

**Goal:** Test execution orchestration.

### Task 14.1: Define test interface and models
- Create src/py_dvt_ate/executive/__init__.py
- Create src/py_dvt_ate/executive/models.py
- TestStatus enum, TestContext, ITest protocol
- **Commit:** "Add test executive models"

### Task 14.2: Implement test logger
- Create src/py_dvt_ate/executive/logger.py
- Log measurements and events
- **Commit:** "Implement test logger"

### Task 14.3: Implement limit checker
- Create src/py_dvt_ate/executive/limits.py
- Evaluate pass/fail against limits
- **Commit:** "Implement limit checker"

### Task 14.4: Implement test sequencer
- Create src/py_dvt_ate/executive/sequencer.py
- Run tests, collect results
- **Commit:** "Implement test sequencer"

---

## Sprint 15: TempCo Characterisation Test

**Goal:** First complete DVT test.

### Task 15.1: Define test base class
- Create src/py_dvt_ate/tests/__init__.py
- Create src/py_dvt_ate/tests/base.py
- Common test utilities
- **Commit:** "Add DVT test base class"

### Task 15.2: Implement TempCo test
- Create src/py_dvt_ate/tests/tempco.py
- Temperature sweep logic
- Vout measurement at each temperature
- TempCo calculation
- **Commit:** "Implement TempCo characterisation test"

### Task 15.3: Add TempCo test integration tests
- Create tests/integration/test_tempco.py
- Full end-to-end test with simulator
- **Commit:** "Add TempCo integration tests"

---

## Sprint 16: CLI Enhancement

**Goal:** Complete CLI for test execution.

### Task 16.1: Add server commands to CLI
- start-server command
- Configure ports via options
- **Commit:** "Add server CLI commands"

### Task 16.2: Add test execution commands
- run-test command
- List available tests
- **Commit:** "Add test execution CLI commands"

### Task 16.3: Add instrument query commands
- Direct instrument query/command
- Useful for debugging
- **Commit:** "Add instrument CLI commands"

---

## Sprint 17: Dashboard Enhancement & Polish

**Goal:** Connect dashboard to full stack + end-to-end verification.

### Task 17.1: Update dashboard to use HAL
- Replace direct physics connection with HAL
- Add instrument status panels
- **Commit:** "Update dashboard to use HAL"

### Task 17.2: Add test execution page
- Run tests from dashboard
- Progress display
- **Commit:** "Add test execution dashboard page"

### Task 17.3: Add results viewer page
- Historical results display
- Basic charts
- **Commit:** "Add results viewer dashboard page"

### Task 17.4: End-to-end integration test
- Create tests/integration/test_e2e.py
- Full workflow: start server, run test, check results
- **Commit:** "Add end-to-end integration test"

### Task 17.5: Update README with usage
- Quick start guide
- Example commands
- Screenshots
- **Commit:** "Update README with usage instructions"

### Task 17.6: Verify test coverage
- Run coverage report
- Add tests for gaps
- **Commit:** "Improve test coverage to 80%+"

---

## File Dependencies Map

```
physics/models.py          → (none)
physics/dut/base.py        → models.py
physics/dut/ldo.py         → base.py, models.py
physics/thermal.py         → models.py
physics/engine.py          → models.py, thermal.py, dut/base.py

dashboard/app.py           → physics/engine.py (Sprint 4, direct connection)

instruments/scpi_parser.py → (none)
instruments/base.py        → scpi_parser.py
instruments/*_sim.py       → base.py, physics/engine.py

transport/base.py          → (none)
transport/tcp.py           → base.py

drivers/base.py            → transport/base.py
drivers/*.py               → base.py

hal/interfaces.py          → (none)
hal/impl/*.py              → interfaces.py, drivers/*.py
hal/factory.py             → interfaces.py, impl/*.py

config/models.py           → (none)
config/loader.py           → models.py

data/models.py             → (none)
data/repository.py         → models.py

executive/models.py        → hal/interfaces.py
executive/*.py             → models.py, data/repository.py

tests/*.py                 → executive/models.py, hal/interfaces.py

dashboard/app.py           → hal/factory.py (Sprint 17, upgraded)
```

---

## Milestone Summary

| Sprint | Milestone | What You Can Demo |
|--------|-----------|-------------------|
| 3 | Physics Working | Unit tests prove thermal coupling |
| 4 | **Visual Demo!** | Interactive Streamlit showing physics |
| 7 | Instruments Done | SCPI simulators respond to commands |
| 8 | Network Ready | TCP server accepts connections |
| 11 | HAL Complete | Abstraction layer swappable |
| 15 | First Test | TempCo characterisation runs |
| 17 | **MVP Complete** | Full end-to-end workflow |

---

**End of Development Plan**