PlantPal/soilProbeNode/README.md

PlantPal

Because knowing when to water your plants is hard

Probe node's features

Battery Monitoring:

• The probe node reads the battery voltage from the analog input (A0) using 10 samples and calculates an average.
• Using a resistor divider (220 kΩ resistors) and known voltage parameters, it converts the ADC reading into an estimated battery voltage.
• The voltage is then mapped to a percentage (for a typical 3.7V LiPo, for example, with 4.2 V as 100% and 3.0 V as 0%) so that you always know the current battery state.

Soil Moisture Sensing:

• The sensor on A3 is read using 20 samples spaced 0.1 seconds apart. This creates an average raw reading that is then mapped into a moisture percentage.
• Calibration values (dry and wet) are used to translate the raw sensor value into a meaningful moisture percentage.

Calibration Mode:

• A physical button on D1 is used to trigger calibration.

1. First press: Enters dry calibration mode. After a 10‑second delay, the device takes 20 samples and averages them to determine the "dry" value.
2. Second press: Enters wet calibration mode with the same process to record the "wet" value.
3. Third press: Finalizes calibration, saves the new calibration values to EEPROM, and exits calibration mode.

• If no user calibration has been performed (or if no valid calibration is present in EEPROM), the node falls back on predefined default calibration values so that it is still usable.

BLE Server & Advertising:

• The probe node sets up a BLE server using the predefined service and characteristic UUIDs.
• It advertises its data (both soil moisture and battery percentage) as BLE characteristics so that a reporter node can connect, read, and process the data.
• The BLE characteristics are updated periodically with the latest sensor readings and notify connected clients.

Deep Sleep for Energy Efficiency:

• For battery-powered operation, once data is reported (or if the device has been awake for a set period), the probe node enters deep sleep (for example, 6 hours). This helps to conserve battery life, yet the device can be woken up—by a button press—for calibration or other interactions.

Overall Integration:

• The node uses EEPROM to store calibration data so that values persist across power cycles.
• The code is structured to average multiple readings (to avoid outliers) and uses delay intervals that ensure stable sensor data.
• Debug output via Serial is available (and can be disabled for production) to assist during development and troubleshooting.