ESP32 Deep Sleep for Battery Sensor Nodes: Timer, Button and MQTT

#include <WiFi.h>
#include <PubSubClient.h>
#include <DHT.h>
#include "esp_sleep.h"

#define SLEEP_MINUTES 10
const uint64_t SLEEP_US = SLEEP_MINUTES * 60ULL * 1000000ULL;

const char* WIFI_SSID = "YourWiFi";
const char* WIFI_PASS = "YourWiFiPassword";
// A static IP skips DHCP and shortens the time Wi-Fi is on
IPAddress ip(192, 168, 1, 77), gw(192, 168, 1, 1), mask(255, 255, 255, 0);
const char* MQTT_HOST = "192.168.1.50";

const int SENSOR_PWR = 25, DHT_PIN = 4, BAT_PIN = 34;
const gpio_num_t WAKE_BTN = GPIO_NUM_33;

RTC_DATA_ATTR uint32_t bootCount = 0;   // survives deep sleep
RTC_DATA_ATTR uint32_t failCount = 0;

DHT dht(DHT_PIN, DHT22);
WiFiClient net;
PubSubClient mqtt(net);

void goToSleep() {
  mqtt.disconnect();
  WiFi.disconnect(true);                  // turn the radio off
  WiFi.mode(WIFI_OFF);
  digitalWrite(SENSOR_PWR, LOW);          // sensor off
  esp_sleep_enable_timer_wakeup(SLEEP_US);
  esp_sleep_enable_ext0_wakeup(WAKE_BTN, 0);  // wake when button pulls LOW
  Serial.println("Sleeping");
  Serial.flush();
  esp_deep_sleep_start();                 // never returns
}

void setup() {
  Serial.begin(115200);
  bootCount++;
  esp_sleep_wakeup_cause_t cause = esp_sleep_get_wakeup_cause();
  const char* why = (cause == ESP_SLEEP_WAKEUP_EXT0)  ? "button" :
                    (cause == ESP_SLEEP_WAKEUP_TIMER) ? "timer"  : "power-on";

  // 1. Power the sensor first; DHT22 needs time after power-up
  pinMode(SENSOR_PWR, OUTPUT);
  digitalWrite(SENSOR_PWR, HIGH);

  // 2. Start Wi-Fi in parallel with the sensor warm-up
  WiFi.mode(WIFI_STA);
  WiFi.config(ip, gw, mask, gw);
  WiFi.begin(WIFI_SSID, WIFI_PASS);

  // 3. Battery voltage: divider halves it, so multiply by 2
  analogSetPinAttenuation(BAT_PIN, ADC_11db);
  float vbat = analogReadMilliVolts(BAT_PIN) * 2 / 1000.0;

  delay(2000);                            // DHT22 warm-up
  dht.begin();
  float t = dht.readTemperature();

  // 4. Wait for Wi-Fi, but never longer than 10 s
  uint32_t start = millis();
  while (WiFi.status() != WL_CONNECTED && millis() - start < 10000) delay(50);
  if (WiFi.status() != WL_CONNECTED) { failCount++; goToSleep(); }

  // 5. Publish one message
  mqtt.setServer(MQTT_HOST, 1883);
  if (mqtt.connect("esp32-batnode", "iotuser", "secret")) {
    char msg[128];
    snprintf(msg, sizeof(msg),
      "{\"temp_c\":%.1f,\"vbat\":%.2f,\"boot\":%lu,\"fails\":%lu,\"wake\":\"%s\",\"ms\":%lu}",
      t, vbat, (unsigned long)bootCount, (unsigned long)failCount, why, millis());
    mqtt.publish("garden/batnode/telemetry", msg);
    mqtt.loop();
    delay(100);                           // let the TCP stack send it
  } else {
    failCount++;
  }
  goToSleep();
}

void loop() {
  // never reached
}