calculate voltage

src/main.cpp

@@ -84,14 +84,14 @@ struct __attribute__((packed)) sensor_readings_t {
   uint32_t voc = 0; // Ohm
   float pm10 = NAN; // µg/m³
   float pm25 = NAN; // µg/m³
-  float lux = NAN;
+  float lux = NAN; // lx
   float uvi = NAN;
   float uva = NAN;
   float uvb = NAN;
   float temperature_max = NAN; // °C
   float temperature_min = NAN; // °C
-  int battery = 0;
-  int8_t rssi = 0;
+  float voltage = NAN; // V
+  int8_t rssi = 0; // dBm
   time_t lastUpdate = 0;
 } sensor_readings;
 
@@ -371,11 +371,12 @@ void getSensorMeasurements() {
     }
   }
 
-  sensor_readings.battery = analogRead(_VBAT);
+  int battery = analogRead(_VBAT);
+  sensor_readings.voltage = (battery/4096.0)*2*3.42;
   sensor_readings.rssi = WiFi.RSSI();
 
   ESP_LOGI(TAG, "RSSI          : %5d    dBm", sensor_readings.rssi);
-  ESP_LOGI(TAG, "Battery       : %5d   ", sensor_readings.battery);
+  ESP_LOGI(TAG, "Battery       : %5d   ", battery);
   ESP_LOGI(TAG, "Heap          : %5lu", ESP.getFreeHeap());
 
   sensor_readings.lastUpdate = getTimestamp();
@@ -417,7 +418,7 @@ void receiveMqtt(const char* topic, const char* data, int data_len) {
           if (jsonDoc.containsKey("uvb")) sensor->uvb = jsonDoc["uvb"].as<float>();
           if (jsonDoc.containsKey("pm10")) sensor->pm10 = jsonDoc["pm10"].as<float>();
           if (jsonDoc.containsKey("pm2.5")) sensor->pm25 = jsonDoc["pm2.5"].as<float>();
-          if (jsonDoc.containsKey("voltage")) sensor->battery = jsonDoc["voltage"].as<int>();
+          if (jsonDoc.containsKey("voltage")) sensor->voltage = jsonDoc["voltage"].as<float>();
           if (jsonDoc.containsKey("rssi")) sensor->rssi = jsonDoc["rssi"].as<int8_t>();
           if (jsonDoc.containsKey("timestamp")) sensor->lastUpdate = jsonDoc["timestamp"].as<time_t>();
           ESP_LOGI(TAG, "got new values from %s, timestamp: %lu", topic, sensor->lastUpdate);
@@ -670,7 +671,7 @@ void sendValues() {
     jsonDoc["pm10"] = sensor_readings.pm10;
     jsonDoc["pm2.5"] = sensor_readings.pm25;
   }
-  jsonDoc["voltage"] = sensor_readings.battery;
+  jsonDoc["voltage"] = sensor_readings.voltage;
   jsonDoc["rssi"] = sensor_readings.rssi;
   jsonDoc["timestamp"] = sensor_readings.lastUpdate;
   serializeJson(jsonDoc, buf, JSON_BUF_LEN);