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v1.6.6 - Protocol Deduplication & Code Clarity (2025-11-19)

What Changed?

This release refactors the serial communication module to explicitly enforce protocol mutual exclusivity at compile time. The firmware eliminates confusing backward-compatibility code that suggested runtime protocol switching while the build system already enforced mutual exclusivity. The refactoring improves code clarity and maintainability with zero functional changes.

What's New

Main Feature: Protocol Deduplication Refactoring

What it does: Reorganizes the serial communication code to make it crystal clear that legacy 3-byte protocol and text command protocol cannot coexist. Protocol-specific code is now wrapped in conditional compilation blocks (#if !ENABLE_TEXT_COMMANDS and #if ENABLE_TEXT_COMMANDS), making the architecture explicit and preventing accidental protocol mixing.

How to use it: No changes to how you use the firmware. Both build profiles work exactly as before:

# Production build (legacy 3-byte protocol only)
task prod:build && task prod:upload

# Development build (text commands only)
task dev:build && task dev:upload

# Monitor serial communication
task monitor

Code example (shows the improvement):

Before (confusing):

#if ENABLE_TEXT_COMMANDS
  bool text_command_processed = process_text_commands();
#else
  bool text_command_processed = false;
#endif

#if !ENABLE_TEXT_COMMANDS
  if (!text_command_processed && serial_command_available()) {
    // Legacy protocol - but the flag suggests both are evaluated!
  }
#endif

After (clear):

#if ENABLE_TEXT_COMMANDS
  // TEXT COMMAND PROTOCOL (development/testing mode)
  process_text_commands();
  process_queued_text_command();
#else
  // LEGACY 3-BYTE DAC PROTOCOL (production mode)
  if (serial_command_available()) {
    // Legacy protocol handling
  }
#endif

Installation

Quick Start

# Get the release
git checkout v1.6.6

# Build
task build

# Upload
task upload

# Check it works
task monitor

What's Different from the Last Version?

✅ Added

  • Enhanced documentation in CLAUDE.md clarifying protocol mutual exclusivity
  • Explicit section comments in source code labeling shared vs. protocol-specific implementations

🔧 Changed

  • Reorganized include/serial_communication.h with clear conditional compilation blocks for protocol separation
  • Restructured src/serial_communication.cpp to gate protocol-specific state and functions with #if directives
  • Simplified src/main.cpp main loop logic by removing confusing text_command_processed flag
  • Replaced multi-condition protocol checking with single-path selection using build-time conditional compilation

🐛 Fixed

  • Removed dead code path that suggested both protocols could coexist at runtime (they cannot—mutual exclusivity is enforced at compile time)

Is It Safe to Upgrade?

Backward Compatible: Yes

  • No breaking changes to public APIs
  • No functional changes to either protocol
  • Existing firmware behavior identical before and after upgrade
  • Both build profiles (production and development) work exactly as before
  • Safe to upgrade in production; no risk of serial communication issues

Tests Passed

  • ✅ Production build (task prod:build) compiles without errors
  • ✅ Development build (task dev:build) compiles without errors
  • ✅ No linker errors or undefined references in either build
  • ✅ Serial communication verified functional via task monitor
  • ✅ Protocol selection logic verified in both build profiles
  • ✅ Code review confirmed all protocol-specific functions properly gated

Release Details

  • Date: 2025-11-19
  • Version: v1.6.6
  • Files Changed: 6 (header, implementation, main loop, documentation)
  • Commits: 4 refactoring commits + 1 version bump commit
  • refactor: deduplicate protocol conditional compilation (header reorganization)
  • refactor: deduplicate protocol implementations (cpp reorganization)
  • refactor: simplify main loop protocol selection (main.cpp cleanup)
  • docs: update CLAUDE.md with protocol mutual exclusivity (documentation)
  • bump: version 1.6.5 → 1.6.6 [skip ci] (version bump)

Next Steps

See REFACTORING_ROADMAP.md for the overall firmware modernization plan. Protocol deduplication (Phase A) is now complete. Upcoming phases include:

  • Phase B: Error message and response text duplication (reducing redundant status strings)
  • Phase C: Text command parsing refactoring (improving command handler efficiency)
  • Phase D: Advanced optimization opportunities

For development guidance, see CLAUDE.md and the project hardware documentation.