Proper battery sense fix (#225)

Fixing consistency + add board dependant battery resistor values

src/batterymonitor.h

@@ -45,6 +45,9 @@
     #define ADCVoltageMax 1.0
 #endif
 
+#ifndef BATTERY_SHIELD_RESISTANCE
+    #define BATTERY_SHIELD_RESISTANCE 180.0
+#endif
 #ifndef BATTERY_SHIELD_R1
     #define BATTERY_SHIELD_R1 100.0
 #endif
@@ -56,7 +59,7 @@
     #ifndef PIN_BATTERY_LEVEL
         #error Internal ADC enabled without pin! Please select a pin.
     #endif
-    // Wemos D1 Mini has an internal Voltage Divider with R1=220K and R2=100K > this means, 3.3V analogRead input voltage results in 1023.0
+    // Wemos D1 Mini has an internal Voltage Divider with R1=100K and R2=220K > this means, 3.3V analogRead input voltage results in 1023.0
     // Wemos D1 Mini with Wemos Battery Shield v1.2.0 or higher: Battery Shield with J2 closed, has an additional 130K resistor. So the resulting Voltage Divider is R1=220K+100K=320K and R2=100K > this means, 4.5V analogRead input voltage results in 1023.0
     // ESP32 Boards may have not the internal Voltage Divider. Also ESP32 has a 12bit ADC (0..4095). So R1 and R2 can be changed.
     // Diagramm: 

src/defines.h

@@ -38,12 +38,12 @@
 //   BAT_MCP3021 for external ADC connected over I2C
 #define BATTERY_MONITOR BAT_EXTERNAL
 
-// BAT_EXTERNAL definition
+// BAT_EXTERNAL definition override
 // D1 Mini boards with ESP8266 have internal resistors. For these boards you only have to adjust BATTERY_SHIELD_RESISTANCE.
 // For other boards you can now adjust the other resistor values.
 // The diagram looks like this:
 //   (Battery)--- [BATTERY_SHIELD_RESISTANCE] ---(INPUT_BOARD)---  [BATTERY_SHIELD_R2] ---(ESP32_INPUT)--- [BATTERY_SHIELD_R1] --- (GND)
-#define BATTERY_SHIELD_RESISTANCE 180 //130k BatteryShield, 180k SlimeVR or fill in external resistor value in kOhm
+// #define BATTERY_SHIELD_RESISTANCE 180 //130k BatteryShield, 180k SlimeVR or fill in external resistor value in kOhm
 // #define BATTERY_SHIELD_R1 100 // Board voltage divider resistor Ain to GND in kOhm
 // #define BATTERY_SHIELD_R2 220 // Board voltage divider resistor Ain to INPUT_BOARD in kOhm
 
@@ -68,6 +68,15 @@
   #define PIN_BATTERY_LEVEL 17
   #define LED_PIN 2
   #define LED_INVERTED true
+  #ifndef BATTERY_SHIELD_RESISTANCE
+    #define BATTERY_SHIELD_RESISTANCE 0
+  #endif
+  #ifndef BATTERY_SHIELD_R1 
+    #define BATTERY_SHIELD_R1 10
+  #endif
+  #ifndef BATTERY_SHIELD_R2
+    #define BATTERY_SHIELD_R2 40.2
+  #endif
 #elif BOARD == BOARD_SLIMEVR_LEGACY || BOARD == BOARD_SLIMEVR_DEV
   #define PIN_IMU_SDA 4
   #define PIN_IMU_SCL 5
@@ -76,6 +85,15 @@
   #define PIN_BATTERY_LEVEL 17
   #define LED_PIN 2
   #define LED_INVERTED true
+  #ifndef BATTERY_SHIELD_RESISTANCE
+    #define BATTERY_SHIELD_RESISTANCE 0
+  #endif
+  #ifndef BATTERY_SHIELD_R1 
+    #define BATTERY_SHIELD_R1 10
+  #endif
+  #ifndef BATTERY_SHIELD_R2
+    #define BATTERY_SHIELD_R2 40.2
+  #endif
 #elif BOARD == BOARD_NODEMCU || BOARD == BOARD_WEMOSD1MINI
   #define PIN_IMU_SDA D2
   #define PIN_IMU_SCL D1
@@ -84,6 +102,15 @@
   #define PIN_BATTERY_LEVEL A0
 //  #define LED_PIN 2
 //  #define LED_INVERTED true
+  #ifndef BATTERY_SHIELD_RESISTANCE
+    #define BATTERY_SHIELD_RESISTANCE 180
+  #endif
+  #ifndef BATTERY_SHIELD_R1 
+    #define BATTERY_SHIELD_R1 100
+  #endif
+  #ifndef BATTERY_SHIELD_R2
+    #define BATTERY_SHIELD_R2 220
+  #endif
 #elif BOARD == BOARD_ESP01
   #define PIN_IMU_SDA 2
   #define PIN_IMU_SCL 0