Merge pull request #823 from claesg/master

Fix for reading battery level on RAK-4631

src/Power.cpp

@@ -43,6 +43,7 @@ Power *power;
 
 using namespace meshtastic;
 
+#ifndef AREF_VOLTAGE
 #if defined(NRF52_SERIES)
 /*
  * Internal Reference is +/-0.6V, with an adjustable gain of 1/6, 1/5, 1/4,
@@ -57,6 +58,7 @@ using namespace meshtastic;
 #else
 #define AREF_VOLTAGE 3.3
 #endif
+#endif
 
 /**
  * If this board has a battery level sensor, set this to a valid implementation
@@ -102,8 +104,12 @@ class AnalogBatteryLevel : public HasBatteryLevel
         if (millis() - last_read_time_ms > min_read_interval) {
             last_read_time_ms = millis();
             uint32_t raw = analogRead(BATTERY_PIN);
-            float scaled = 1000.0 * ADC_MULTIPLIER * (AREF_VOLTAGE / 1024.0) * raw;
-            
+            float scaled;
+            #ifndef VBAT_RAW_TO_SCALED
+            scaled = 1000.0 * ADC_MULTIPLIER * (AREF_VOLTAGE / 1024.0) * raw;
+            #else
+            scaled = VBAT_RAW_TO_SCALED(raw); //defined in variant.h
+            #endif
             // DEBUG_MSG("battery gpio %d raw val=%u scaled=%u\n", BATTERY_PIN, raw, (uint32_t)(scaled));
             last_read_value = scaled;
             return scaled;
@@ -136,7 +142,9 @@ class AnalogBatteryLevel : public HasBatteryLevel
     const float fullVolt = 4200, emptyVolt = 3270, chargingVolt = 4210, noBatVolt = 2230;
     float last_read_value = 0.0;
     uint32_t last_read_time_ms = 0;
-} analogLevel;
+};
+
+AnalogBatteryLevel analogLevel;
 
 Power::Power() : OSThread("Power") {}
 
@@ -153,11 +161,19 @@ bool Power::analogInit()
     adcAttachPin(BATTERY_PIN);
 #endif
 #ifdef NRF52_SERIES
+#ifdef VBAT_AR_INTERNAL
+     analogReference(VBAT_AR_INTERNAL);
+#else
     analogReference(AR_INTERNAL); // 3.6V
 #endif
+#endif
 
+#ifndef BATTERY_SENSE_RESOLUTION_BITS
+#define BATTERY_SENSE_RESOLUTION_BITS 10
+#endif
+    
     // adcStart(BATTERY_PIN);
-    analogReadResolution(10); // Default of 12 is not very linear. Recommended to use 10 or 11 depending on needed resolution.
+    analogReadResolution(BATTERY_SENSE_RESOLUTION_BITS); // Default of 12 is not very linear. Recommended to use 10 or 11 depending on needed resolution.
     batteryLevel = &analogLevel;
     return true;
 #else

variants/WisCore_RAK4631_Board/variant.h

@@ -171,8 +171,25 @@ static const uint8_t SCK = PIN_SPI_SCK;
 #define GPS_RX_PIN PIN_SERIAL1_RX
 #define GPS_TX_PIN PIN_SERIAL1_TX
 
-// The battery sense is hooked to pin A0
+// Battery
+// The battery sense is hooked to pin A0 (5)
 #define BATTERY_PIN PIN_A0
+// and has 12 bit resolution
+#define BATTERY_SENSE_RESOLUTION_BITS 12
+#define BATTERY_SENSE_RESOLUTION 4096.0
+// Definition of milliVolt per LSB => 3.0V ADC range and 12-bit ADC resolution = 3000mV/4096
+#define VBAT_MV_PER_LSB (0.73242188F)
+// Voltage divider value => 1.5M + 1M voltage divider on VBAT = (1.5M / (1M + 1.5M))
+#define VBAT_DIVIDER (0.4F)
+// Compensation factor for the VBAT divider
+#define VBAT_DIVIDER_COMP (1.73)
+// Fixed calculation of milliVolt from compensation value
+#define REAL_VBAT_MV_PER_LSB (VBAT_DIVIDER_COMP * VBAT_MV_PER_LSB)
+#undef AREF_VOLTAGE
+#define AREF_VOLTAGE 3.0
+#define VBAT_AR_INTERNAL AR_INTERNAL_3_0
+#define ADC_MULTIPLIER VBAT_DIVIDER_COMP //REAL_VBAT_MV_PER_LSB
+#define VBAT_RAW_TO_SCALED(x) (REAL_VBAT_MV_PER_LSB * x)
 
 #ifdef __cplusplus
 }