Implemented battery voltage measurement for Heltec WiFi LoRa 32 V3 (#16)

Added voltage divider and ADC input control pin for ARDUINO_heltec_wifi_lora_32_V3

BresserWeatherSensorLWCfg.h

@@ -40,7 +40,9 @@
 // 20240410 Removed obsolete defines
 // 20240413 Refactored ADC handling
 // 20240423 Added define ARDUINO_heltec_wifi_lora_32_V3
-// 20240427 Added BLE configuration/status via LoRaWAN
+// 20240427 Added voltage divider and ADC input control pin
+//          for ARDUINO_heltec_wifi_lora_32_V3
+//          Added BLE configuration/status via LoRaWAN
 // 20240430 Modified battery voltage measurement
 //
 // Note:
@@ -500,6 +502,10 @@ const uint8_t ADC3_SAMPLES = 10;
 // Voltage divider R1 / (R1 + R2) -> V_meas = V(R1 + R2); V_adc = V(R1)
 #if defined(ARDUINO_THINGPULSE_EPULSE_FEATHER)
 const float UBATT_DIV = 0.6812;
+#elif defined(ARDUINO_heltec_wifi_32_lora_V3) || defined(ARDUINO_heltec_wifi_lora_32_V3)
+#define ADC_CTRL 37
+// R17=100k, R14=390k => 100k / (100k + 390 k)
+const float UBATT_DIV = 0.2041;
 #else
 const float UBATT_DIV = 0.5;
 #endif

src/adc/adc.cpp

@@ -35,6 +35,8 @@
 // 20240414 Added ESP32-S3 PowerFeather
 //          Added getSupplyVoltage()
 // 20240423 Added define ARDUINO_heltec_wifi_lora_32_V3
+// 20240427 Added ADC input control and battery voltage measurement
+//          for ARDUINO_heltec_wifi_lora_32_V3
 // 20240430 Modified getBatteryVoltage()
 //
 // ToDo:
@@ -81,7 +83,15 @@ uint16_t getBatteryVoltage(void)
     defined(ARDUINO_THINGPULSE_EPULSE_FEATHER)
   // Here come the good guys...
   return getVoltage();
-
+#elif defined(ARDUINO_heltec_wifi_32_lora_V3) || defined(ARDUINO_heltec_wifi_lora_32_V3)
+     // Enable ADC input switch, measure voltage and disable ADC input switch
+    uint16_t voltage;
+    pinMode(ADC_CTRL, OUTPUT);
+    digitalWrite(ADC_CTRL, LOW);
+    delay(100);
+    voltage = getVoltage();
+    pinMode(ADC_CTRL, INPUT);
+    return voltage;
 #elif defined(ARDUINO_ARCH_RP2040)
   // Not implemented - no default VBAT input circuit (connect external divider to A0)
   return 0;