include battery voltage in current weather

src/battery.h

@@ -0,0 +1,19 @@
+#ifndef _UWEATHER_BATTERY_H_
+#define _UWEATHER_BATTERY_H_
+
+#include <Arduino.h>
+
+const int BATT_IN_PIN = A0;
+
+double battery_read_voltage()
+{
+  int acc = analogRead(BATT_IN_PIN);
+  int i = 0;
+  while (i < 10) {
+      acc += analogRead(BATT_IN_PIN);
+      i++;
+  }
+  return (double) acc * .00042; // TODO: check this against a multimeter
+}
+
+#endif /** _UWEATHER_BATTERY_H_ include guard */

src/web.cpp

@@ -6,6 +6,7 @@
 #include <QueryString.h>
 #include "config.h"
 #include "version.h"
+#include "battery.h"
 
 /**
  * How long to wait after the OK to shutdown before no longer
@@ -80,13 +81,19 @@ void handle_firmware(HttpRequest& req, HttpResponse& res)
 
 void handle_weather_current(HttpRequest& req, HttpResponse& res)
 {
-  char buff[3][10] = {};
+  char buff[4][10] = {};
   dtostrf(BME.readTemperature(), 2, 1, buff[0]);
   dtostrf(BME.readPressure(), 2, 1, buff[1]);
   dtostrf(BME.readHumidity(), 2, 1, buff[2]);
+  dtostrf(battery_read_voltage(), 2, 1, buff[3]);
   Serial.printf("temp= %s, pres= %s, hum=%s\r\n", buff[0], buff[1], buff[2]);
   res.headers.set("Content-Type", "application/json");
-  content.printf("{\"time\": null, \"temperature\": %s, \"pressure\": %s, \"humidity\": %s}", buff[0], buff[1], buff[2]);
+  content.printf("{\"time\": null, \"temperature\": %s, \"pressure\": %s, \"humidity\": %s, \"battery_voltage\": %s}",
+      buff[0], 
+      buff[1], 
+      buff[2],
+      buff[3]
+    );
 }
 
 // Handle WiFi Scan