feat: implement deep sleep for battery operation (#5)#8
feat: implement deep sleep for battery operation (#5)#8addidea wants to merge 1 commit intoClawland-AI:mainfrom
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Closes Clawland-AI#5 Complete deep sleep implementation with battery management: **Core Example (examples/deep_sleep/deep_sleep.ino)**: - Timer-based wakeup (configurable, default 5min) - Boot counter persists in RTC memory - Battery voltage monitoring via ADC - Low-battery protection (extends sleep interval) - Fast WiFi reconnect (~2s) - MQTT publish → disconnect → sleep cycle - Ultra-low power: ~30µA (vs ~160mA awake) **Battery Life Calculations**: - 1000mAh LiPo battery - 5-minute interval: 15.7 days - 15-minute interval: 1.5 months - 1-hour interval: 5.5 months - Detailed math included in code comments **Documentation (examples/deep_sleep/README.md)**: - Battery connection wiring (voltage divider for ADC) - Configuration guide (WiFi, MQTT, sleep interval) - Flashing instructions (PlatformIO + Arduino IDE) - Expected serial output example - Troubleshooting (won't wake, battery drain, ADC errors, boot loop) - Power optimization tips (static IP, TX power, sensor control) - Next steps for advanced features **Features**: - Production-ready with error handling - Graceful degradation on low battery - Safe ADC voltage divider design (2:1 ratio) - Multiple wakeup sources supported (timer, GPIO) - OTA update compatible (wake on demand) Expected battery life: 15 days to 5+ months depending on interval! 🔋
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| // Optional: Disable WiFi and BT power during sleep (default) | ||
| esp_sleep_pd_config(ESP_PD_DOMAIN_RTC_PERIPH, ESP_PD_OPTION_OFF); | ||
| esp_sleep_pd_config(ESP_PD_DOMAIN_RTC_SLOW_MEM, ESP_PD_OPTION_OFF); |
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Powering off RTC slow memory destroys persistent boot counter
High Severity
bootCount is declared with RTC_DATA_ATTR, which stores it in RTC slow memory so it persists across deep sleep cycles. However, enterDeepSleep() explicitly calls esp_sleep_pd_config(ESP_PD_DOMAIN_RTC_SLOW_MEM, ESP_PD_OPTION_OFF), which powers off RTC slow memory during sleep. This erases bootCount (and any other RTC_DATA_ATTR variables) every cycle, making the boot counter always read 1. This defeats one of the key advertised features.
Additional Locations (1)
| Serial.println("⚠️ MQTT connection failed, retrying..."); | ||
| delay(1000); | ||
| attempts++; | ||
| } |
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MQTT attempted without checking WiFi connection status
Medium Severity
setupWiFi() doesn't return a success/failure status, and the code proceeds to attempt MQTT connection regardless of WiFi state. When WiFi fails, the code wastes battery power on up to 4 futile connectMQTT() calls plus 3 seconds of delay. For a battery-powered deep sleep device, this unnecessary awake time significantly impacts battery life.
| if (batteryVoltage < LOW_BATTERY_THRESHOLD) { | ||
| Serial.println("⚠️ LOW BATTERY! Extending sleep interval..."); | ||
| esp_sleep_enable_timer_wakeup(SLEEP_INTERVAL_SECONDS * 2 * uS_TO_S_FACTOR); | ||
| esp_deep_sleep_start(); // Go to sleep immediately |
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Low-battery sleep path missing Serial.flush before sleep
Low Severity
The low-battery early sleep path calls esp_deep_sleep_start() immediately after printing the "LOW BATTERY!" message without calling Serial.flush() first. Since deep sleep resets the CPU, buffered UART data is lost. The normal sleep path in enterDeepSleep() correctly calls Serial.flush() before sleeping. This means the diagnostic message that would help a user debug unexpected sleep behavior may never appear on the serial monitor.
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Description
Complete deep sleep implementation for ultra-low-power battery operation.
Closes #5
What's Included
✅ Deep Sleep Example (
examples/deep_sleep/deep_sleep.ino)✅ Battery Life Calculations (included in code)
With 1000mAh LiPo:
✅ Complete Documentation (
examples/deep_sleep/README.md)Key Features
Battery Wiring
Power Consumption
Example Output
Next Steps
Ready for remote, battery-powered deployments! 🔋
Note
Low Risk
Low risk: adds a self-contained example and documentation only, with no changes to core library/runtime behavior.
Overview
Adds a new
examples/deep_sleepArduino sketch that cycles wake → WiFi connect → MQTT publish → disconnect → deep sleep, with timer-based wakeups, RTC-persisted boot counting, and ADC battery-voltage measurement.Includes low-battery behavior (auto-extends sleep interval and sleeps immediately), plus a companion README documenting wiring (voltage divider), configuration, flashing/monitoring, troubleshooting, and battery-life estimates.
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