Solar-Powered Plant Watering

#include <Arduino.h>
#include <Wire.h>
#include <esp_sleep.h>
#include <Preferences.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>


// Forward declarations
int readAverage(int pin);
float readBatteryVoltage();
bool encoderPressed();
void drawStatus();
void drawSetting(uint8_t page);
void saveSettings();
void settingsMode();
void sleepUntilNextCheck();

constexpr int SOIL_PIN = 34;
constexpr int BATTERY_PIN = 35;
constexpr int PUMP_PIN = 25;
constexpr int ENCODER_CLK_PIN = 16;
constexpr int ENCODER_DT_PIN = 17;
constexpr int ENCODER_SW_PIN = 33;
constexpr int SDA_PIN = 21;
constexpr int SCL_PIN = 22;
constexpr uint8_t OLED_ADDRESS = 0x3C;
constexpr int SCREEN_WIDTH = 128;
constexpr int SCREEN_HEIGHT = 64;
constexpr float DIVIDER_RATIO = 127.0f / 27.0f;
constexpr uint32_t CHECK_SECONDS = 300;
constexpr int DEFAULT_DRY_THRESHOLD = 2500;
constexpr uint32_t DEFAULT_WATER_MS = 8000;
constexpr uint32_t DEFAULT_GAP_MINUTES = 60;

Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);
Preferences preferences;
int dryThreshold;
uint32_t waterTimeMs;
uint32_t gapMinutes;
RTC_DATA_ATTR uint32_t secondsSinceWater = DEFAULT_GAP_MINUTES * 60;
RTC_DATA_ATTR bool soilWasDry = false;

int readAverage(int pin) {
  uint32_t total = 0;
  for (int i = 0; i < 12; ++i) {
    total += analogRead(pin);
    delay(10);
  }
  return total / 12;
}

float readBatteryVoltage() {
  return (readAverage(BATTERY_PIN) / 4095.0f) * 3.3f * DIVIDER_RATIO;
}

bool encoderPressed() {
  if (digitalRead(ENCODER_SW_PIN) != LOW) return false;
  delay(25);
  if (digitalRead(ENCODER_SW_PIN) != LOW) return false;
  while (digitalRead(ENCODER_SW_PIN) == LOW) delay(5);
  return true;
}

void drawStatus() {
  const int soil = readAverage(SOIL_PIN);
  const float battery = readBatteryVoltage();
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0, 0);
  display.print("Hydroponics ready");
  display.setCursor(0, 18);
  display.print("Battery: ");
  display.print(battery, 1);
  display.println(" V");
  display.print("Sensor:  ");
  display.println(soil);
  display.setCursor(0, 52);
  display.print("Press knob: settings");
  display.display();
}

void drawSetting(uint8_t page) {
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0, 0);
  if (page == 0) {
    display.println("Dry threshold");
    display.setTextSize(2); display.println(dryThreshold);
  } else if (page == 1) {
    display.println("Pump seconds");
    display.setTextSize(2); display.println(waterTimeMs / 1000UL);
  } else {
    display.println("Minimum gap min");
    display.setTextSize(2); display.println(gapMinutes);
  }
  display.setTextSize(1);
  display.setCursor(0, 52);
  display.print("Turn=change Press=next");
  display.display();
}

void saveSettings() {
  preferences.putInt("dry", dryThreshold);
  preferences.putUInt("water", waterTimeMs);
  preferences.putUInt("gap", gapMinutes);
}

void settingsMode() {
  uint8_t page = 0;
  int lastClk = digitalRead(ENCODER_CLK_PIN);
  uint32_t lastAction = millis();
  drawSetting(page);

  while (millis() - lastAction < 60000UL) {
    const int clk = digitalRead(ENCODER_CLK_PIN);
    if (clk != lastClk && clk == LOW) {
      const bool clockwise = digitalRead(ENCODER_DT_PIN) != clk;
      if (page == 0) dryThreshold = constrain(dryThreshold + (clockwise ? 50 : -50), 0, 4000);
      if (page == 1) waterTimeMs = constrain(waterTimeMs + (clockwise ? 1000 : -1000), 1000, 60000);
      if (page == 2) gapMinutes = constrain(gapMinutes + (clockwise ? 5 : -5), 5, 720);
      drawSetting(page);
      lastAction = millis();
    }
    lastClk = clk;

    if (encoderPressed()) {
      lastAction = millis();
      if (page == 2) {
        saveSettings();
        display.clearDisplay();
        display.setTextSize(1); display.setTextColor(SSD1306_WHITE);
        display.setCursor(0, 24); display.print("Settings saved");
        display.display();
        delay(1000);
        return;
      }
      ++page;
      drawSetting(page);
    }
    delay(2);
  }
  saveSettings();
}

void sleepUntilNextCheck() {
  digitalWrite(PUMP_PIN, LOW);
  display.clearDisplay();
  display.display();
  display.ssd1306_command(SSD1306_DISPLAYOFF);
  esp_sleep_enable_timer_wakeup(static_cast<uint64_t>(CHECK_SECONDS) * 1000000ULL);
  esp_sleep_enable_ext0_wakeup(static_cast<gpio_num_t>(ENCODER_SW_PIN), LOW);
  esp_deep_sleep_start();
}

void setup() {
  pinMode(PUMP_PIN, OUTPUT);
  digitalWrite(PUMP_PIN, LOW);
  pinMode(ENCODER_CLK_PIN, INPUT_PULLUP);
  pinMode(ENCODER_DT_PIN, INPUT_PULLUP);
  pinMode(ENCODER_SW_PIN, INPUT_PULLUP);
  analogReadResolution(12);
  analogSetPinAttenuation(BATTERY_PIN, ADC_11db);
  Wire.begin(SDA_PIN, SCL_PIN);
  display.begin(SSD1306_SWITCHCAPVCC, OLED_ADDRESS);
  preferences.begin("hydro", false);
  dryThreshold = preferences.getInt("dry", DEFAULT_DRY_THRESHOLD);
  waterTimeMs = preferences.getUInt("water", DEFAULT_WATER_MS);
  gapMinutes = preferences.getUInt("gap", DEFAULT_GAP_MINUTES);

  if (esp_sleep_get_wakeup_cause() == ESP_SLEEP_WAKEUP_EXT0) {
    settingsMode();
    sleepUntilNextCheck();
  }

  const int soil = readAverage(SOIL_PIN);
  if (soil >= dryThreshold) soilWasDry = true;
  else if (soil <= dryThreshold - 100) soilWasDry = false;

  if (soilWasDry && secondsSinceWater >= gapMinutes * 60UL) {
    display.clearDisplay();
    display.setTextSize(1); display.setTextColor(SSD1306_WHITE);
    display.setCursor(0, 24); display.print("Pump running...");
    display.display();
    digitalWrite(PUMP_PIN, HIGH);
    delay(waterTimeMs);
    digitalWrite(PUMP_PIN, LOW);
    secondsSinceWater = 0;
  } else {
    secondsSinceWater = min(86400UL, secondsSinceWater + CHECK_SECONDS);
  }

  drawStatus();
  delay(3000);
  sleepUntilNextCheck();
}

void loop() {}