feat(spoolbuddy): scale auto-calibration and manual recalibrate button

[khaosdoctor]

Description

Adds automatic calibration for the NAU7802 + load cell scale to correct thermal and mechanical drift, plus a manual recalibration button in the SpoolBuddy settings UI.

Related Issue

N/A

Documentation

Pick one:

• No docs update required — reason: SpoolBuddy scale feature, no user-facing config changes

Type of Change

• New feature (non-breaking change that adds functionality)
• Test addition or update

Changes Made

• Auto-zero detection: when the scale reads within ±5g and is stable for 10s (with 60s cooldown), runs NAU7802 system offset calibration (mode=2) to re-tare the scale automatically
• Periodic AFE recalibration: runs internal offset calibration (mode=0) every 6 hours to compensate for thermal drift, safe to run with a spool on the scale
• Manual recalibrate button: new "Recalibrate Scale" button in SpoolBuddy settings (scale tab) that triggers both calibrations via the existing diagnostic queue/poll infrastructure and displays results in a terminal-style modal
• Tests: added test coverage for auto-zero detection, calibrate_zero, and AFE recalibration in scale_reader

Files changed

• spoolbuddy/daemon/scale_reader.py — auto-zero detection loop, calibrate_zero(), recalibrate_afe() methods
• spoolbuddy/daemon/main.py — run_recalibrate_diag command handler
• spoolbuddy/tests/test_scale_reader.py — new test file (176 lines)
• backend/app/api/routes/spoolbuddy.py — added "recalibrate" to diagnostic validation
• frontend/src/api/client.ts — extended diagnostic type unions
• frontend/src/components/SpoolBuddySettings.tsx — recalibrate button + modal
• frontend/src/components/spoolbuddy/DiagnosticModal.tsx — recalibrate type + title

Testing

• I have tested this on my local machine
• I have tested with my printer model: A1 Mini (SpoolBuddy with NAU7802 + load cell)

Checklist

• My code follows the project's coding style
• My changes generate no new warnings
• I have tested my changes thoroughly

Additional Notes

All 90 daemon tests pass. The auto-zero only triggers when the scale is genuinely empty and stable, with a 60s cooldown to avoid rapid re-calibration loops. The periodic internal recal (mode=0) is safe with a spool on the scale since it only recalibrates the ADC's internal analog front-end.

[Copilot]

🟡 Changes recommended

The new recalibration diagnostic currently relies on private ScaleReader internals and reports potentially misleading success/messaging, and there are unprofessional/unclear comment markers that should be cleaned up.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Adds scale drift-mitigation and user-triggered calibration flows for SpoolBuddy by introducing auto-zero detection, periodic NAU7802 AFE recalibration, and a new “recalibrate” diagnostic surfaced in the UI and API.

Changes:

• Implemented auto-zero detection and zero-point calibration logic in the scale reader, plus periodic AFE recalibration.
• Added a new recalibrate diagnostic command handler in the daemon and wired it through backend validation + frontend client/modal UI.
• Added test coverage for auto-zero detection, calibrate_zero(), and AFE recalibration behavior.

File summaries

File	Description
spoolbuddy/daemon/scale_reader.py	Adds auto-zero state machine, calibrate_zero(), and periodic recalibrate_afe() support.
spoolbuddy/daemon/main.py	Runs auto-zero + periodic recal in the scale poll loop and adds run_recalibrate_diag handler.
spoolbuddy/tests/test_scale_reader.py	New unit tests covering auto-zero detection, zero calibration, and AFE recalibration.
backend/app/api/routes/spoolbuddy.py	Allows recalibrate as a diagnostic type for queue/result endpoints.
frontend/src/api/client.ts	Extends diagnostics type unions to include recalibrate.
frontend/src/components/SpoolBuddySettings.tsx	Adds “Recalibrate Scale” button and opens diagnostic modal.
frontend/src/components/spoolbuddy/DiagnosticModal.tsx	Adds recalibrate type and title handling.

Review details

Suppressed comments (2)

spoolbuddy/daemon/main.py:354

• calibrate_zero() returns a tare offset even when it falls back to software adjustment after a hardware calibration failure, so reporting "System offset cal: OK" here can be misleading. Also, the else branch (skipped (not pending)) is effectively unreachable because _auto_zero_pending is set immediately before calling calibrate_zero(). Consider using neutral wording that reflects the fallback behavior and removing the dead branch.

                        lines.append(f"    System offset cal: OK (new tare={new_tare})")
                    else:
                        lines.append("    System offset cal: skipped (not pending)")

spoolbuddy/daemon/main.py:372

• The diagnostic success flag only reflects the internal offset calibration result (afe_ok) and ignores the outcome of the zero calibration step, so the UI may show overall success even if step [2] fails/throws. Track a separate zero_ok (even if just new_tare is not None) and combine them for the final success/exit_code.

                    success = afe_ok

• Files reviewed: 7/7 changed files
• Comments generated: 1
• Review effort level: Lite

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