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## Summary Continue my experiment from https://github.com/crosspoint-reader/crosspoint-reader/pull/801 This PR add the ability to lower the CPU frequency on extended idle period (currently set to 3 seconds). By default, the esp32c3 CPU is set to 160MHz, and now on idle, we can reduce it to just 10MHz. Note that while this functionality is already provided by [esp power management](https://docs.espressif.com/projects/esp-idf/en/v4.3/esp32c3/api-reference/system/power_management.html), the current Arduino build lacks of this, and enabling it is just too complicated (not worth the effort compared to this PR) Update: more info in https://github.com/crosspoint-reader/crosspoint-reader/pull/852#issuecomment-3904562827 ## Testing Pre-condition for each test case: the battery is charged to 100%, and is left plugged in after fully charged for an extra 1 hour. The table below shows how much battery is **used** for a given duration: | case / duration | 6 hrs | 12 hrs | | --- | --- | --- | | `delay(10)` | 26% | 48% | | `delay(50)`, PR https://github.com/crosspoint-reader/crosspoint-reader/pull/801 | 20% | Not tested | | `delay(50)` + low CPU freq (This PR) | Not tested | 25% | | `delay(10)` + low CPU freq (1) | Not tested | Not tested | (1) I decided not to test this case because it may not make sense. The problem is that CPU frequency vs power consumption do not follow a linear relationship, see [this](https://www.arrow.com/en/research-and-events/articles/esp32-power-consumption-can-be-reduced-with-sleep-modes) as an example. So, tight loop (10ms) + lower CPU freq significantly impact battery life, because the active CPU time is now much higher compared to the wall time. **So in conclusion, this PR improves ~150% to ~200% battery use time per charge.** The projected battery life is now: ~36-48 hrs of reading time (normal reading, no wifi) --- ### AI Usage While CrossPoint doesn't have restrictions on AI tools in contributing, please be transparent about their usage as it helps set the right context for reviewers. Did you use AI tools to help write this code? **NO**
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