[DRSDavidSoft]

Closes #584.

Root cause

The firmware UART service had drained HardwareSerial until available() reached zero since the initial firmware commit. A removed or noisy USB-UART bridge can keep adding input, monopolizing the MCU loop and starving autonomous keys, relays, displays, LEDs, audio, telemetry, and completion of the watchdog-supervised loop.

Fix

• snapshot the ATmega328P UART ring occupancy on entry and drain only that bounded set
• leave bytes arriving during the pass for the next cooperative firmware loop
• preserve incremental framing across calls, including maximum-size frames
• add native regression coverage for sustained noise, delimiter recovery, and multi-pass frame processing

Verification

• focused UART protocol CTest: passed
• complete VirtualBoard/firmware CTest: 19/19 passed before the size-only refinement
• full AVR firmware compile through project Controller tooling: passed
• default full profile retained: hosted CI reports 32,248 / 32,384 application bytes
• optional EEPROM-menu-label profile compiles locally without disabling any feature; estimated SRAM margin 280 bytes
• live control case before code change: host serial closed for 8 seconds and reconnected without watchdog reset, distinguishing normal handle close from physical/noisy adapter loss

No Go build/test was run in this pass.

[Copilot]

Copilot review overview

🟢 Approval recommended

The bounded receive loop addresses UART starvation while retaining framing behavior and targeted regression coverage.

Review effort: Balanced
Findings: None

What changed in this PR

Bounds UART receive work to keep firmware services responsive during noisy or failed host connections.

Changes:

• Limits each UART service pass to 32 bytes and handles failed reads.
• Preserves incremental frame parsing across service calls.
• Adds regression coverage for noise, read failures, and recovery.

File	Description
Project/​UartProtocol.cpp	Implements bounded, failure-aware UART reads.
Project/​UartProtocol.h	Defines the receive-byte budget.
Tools/​VirtualBoard/​tests/​uart_protocol_test.cpp	Tests bounded processing and recovery.
Tools/​VirtualBoard/​tests/​arduino_mock/​Arduino.h	Adds simulated serial read failures.

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[Copilot]

Copilot review overview

🟢 Approval recommended

The bounded processing logic is consistent with AVR ring behavior and has focused regression coverage.

Review effort: Balanced
Findings: None