slightly more sophisticated battery monitoring, with charge status

src/battery.h

@@ -4,16 +4,53 @@
 #include <Arduino.h>
 
 const int BATT_IN_PIN = A0;
+const int BATTERY_CHECK_INTERVAL = 5000;
 
-double battery_read_voltage()
+typedef struct battery_info_t
 {
-  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
+    uint last_raw = 0;
+    int last_delta = 0;
+    unsigned long last_millis = 0;
+    bool is_charging = false;
+};
+
+battery_info_t Battery;
+
+float battery_get_voltage()
+{
+    return (float) Battery.last_raw * .00042;
+}
+
+void uweather_handle_battery()
+{
+    unsigned long now = millis();
+    if (Battery.last_millis + BATTERY_CHECK_INTERVAL > now) {
+        return; // just checked, nothing to do
+    }
+
+    // Read voltage
+    unsigned int raw = 0;
+    int i = 0;
+    analogRead(BATT_IN_PIN); // throw away first reading
+    while (i < 10) {
+        raw += analogRead(BATT_IN_PIN);
+        i++;
+    }
+    
+    // Calculate delta
+    int delta = raw - Battery.last_raw;
+
+    // Determine if charging
+    if (delta > 0) {
+        Battery.is_charging = true;
+    } else if (delta < 0) {
+        Battery.is_charging = false;
+    }
+
+    // Save values
+    Battery.last_raw = raw;
+    Battery.last_delta = delta;
+    Battery.last_millis = now;
 }
 
 #endif /** _UWEATHER_BATTERY_H_ include guard */

src/web.cpp

@@ -85,14 +85,15 @@ void handle_weather_current(HttpRequest& req, HttpResponse& res)
   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]);
+  dtostrf(battery_get_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, \"battery_voltage\": %s}",
+  content.printf("{\"time\": null, \"temperature\": %s, \"pressure\": %s, \"humidity\": %s, \"battery\": { \"voltage\": %s, \"is_charging\": %s}}",
       buff[0], 
       buff[1], 
       buff[2],
-      buff[3]
+      buff[3],
+      (Battery.is_charging ? "true":"false")
     );
 }
 
@@ -287,6 +288,7 @@ void uweather_web_init(void)
 void uweather_web_handle(void)
 {
     if (web_is_shutdown) return;
+    uweather_handle_battery();
     if (web_shutdown_at) {
         unsigned long now = millis();
         if (now > web_shutdown_at) {