[DRSDavidSoft]

The host acknowledged strip frames while the physical strip remained dark. GCC assigned both the mutable next-bit operand and the constant low-port value to r24, preventing low transitions. Early-clobber constraints, a read/write pointer and a memory clobber correct the sender. A linked-AVR waveform gate checks all byte values, boundaries and full frames.

The user physically confirmed rainbow output with corrected firmware BC491357. They also reported low FPS: complete 100-pixel frame commands measured 66–76 ms, and the old 50 ms scheduling grid waited until 100 ms. Late frames now render current animation time immediately and rebase without stale-frame bursts.

Validation:

• Old linked image fails the register-alias regression; corrected image passes every waveform case.
• MiniCore compile: 32,280 bytes flash, 1,570 bytes static SRAM, 231-byte stack margin.
• Guarded firmware upload, complete flash readback, settings restore and authentication succeeded.
• Focused strip Go tests and all 94 build-tooling tests pass. Local Go testing used 1.27.1 with an external modfile because the pinned 1.27.2 download returned HTTP 403; repository pins are unchanged.
• All PR CI checks pass, including Windows host and AVR firmware.
• Rechecked 2026-10-20: board connection recovered. Installed the verified Windows CI host 0.0.0-ci.1631 from merge bff7a15, containing this branch and current main. Full 100-pixel rainbow is streaming, including successful dispatch through Pealayer's hardware.strip.rainbow RPC.
• Pealayer is connected to the physical board. Native visual connection, health, JSON-RPC, smoke exit 0 and no new crash events were verified. No media is currently decoded; synchronized playback/cues and physical motion are not accepted by this evidence. Physical smoothness after the pacing change remains unconfirmed.

Handoff: branch fix/strip-register-constraints, commit 7374de4, verified on GitHub. Relevant source worktrees are clean. Corrected firmware BC491357 remains installed. The updated installed host is streaming the full rainbow, and Pealayer is connected.

Remaining: rising framing errors with zero CRC errors and stable reset count (#696); helper-driven host self-update staging (#695); programmer adapter compatibility (#694). After self-update retained the original image, the verified candidate was activated with the old host stopped and rollback retained. Private backups, device/config state and screenshots remain local. Stop strip streaming before precise MCU recording/playback. No production timing guarantee is claimed.

Related: #71, #390, standalone FastLED comparison #692.