29 lines
2.0 KiB
Markdown
29 lines
2.0 KiB
Markdown
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# Fix Idle Freeze: NTP Power Lock and Clock Refresh Hardening
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**Date**: 2026-03-09
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## Task Description
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Fix device freeze during idle, where the device stops responding to button presses after idling on the Home screen and requires a hard reset. Root cause was the mod-specific clock refresh logic in the main loop triggering a display render while the CPU is at reduced frequency (10 MHz low-power mode), combined with the background BootNtpSync task running WiFi/NTP operations without holding a power lock.
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## Root Cause
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The freeze coincides with the clock minute boundary. The mod's clock refresh code detects the minute change and calls `activityManager.requestUpdate()`, triggering a Home screen render while the CPU is at 10 MHz. SPI display operations at reduced APB frequency can deadlock the display communication. Additionally, `BootNtpSync` runs WiFi/NTP on a background task with no power lock, risking instability during WiFi teardown when the main loop may enter low-power mode.
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## Changes Made
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### 1. `src/util/BootNtpSync.cpp`
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- Added `#include <HalPowerManager.h>`
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- Added `HalPowerManager::Lock powerLock;` at the top of `taskFunc()` to keep the CPU at full speed for the entire duration of WiFi scanning, connection, NTP sync, and teardown
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### 2. `src/main.cpp` (clock refresh block, ~lines 408-428)
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- In the `sawInvalidTime` branch: added `lastActivityTime = millis()` and `powerManager.setPowerSaving(false)` before calling `requestUpdate()`
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- In the minute-change branch: added `lastActivityTime = millis()` and `powerManager.setPowerSaving(false)` before calling `requestUpdate()`
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- This ensures the CPU is restored to 160 MHz before any render-related code executes and prevents immediate re-entry into low-power mode
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## Follow-up Items
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- Verify on device that the freeze no longer occurs after idling for extended periods
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- Monitor heap usage to confirm the power lock doesn't introduce memory issues
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- Test that NTP sync still completes successfully with the power lock in place
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