Update adc_vbat.ino to also work with nrf52840

Author: pyro9

libraries/Bluefruit52Lib/examples/Hardware/adc_vbat/adc_vbat.ino

@@ -1,10 +1,21 @@
-#define VBAT_PIN          (A7)
+
 #define VBAT_MV_PER_LSB   (0.73242188F)   // 3.0V ADC range and 12-bit ADC resolution = 3000mV/4096
+
+#ifdef NRF52840_XXAA    // if this is for nrf52840
+#define VBAT_PIN (A6)
+#define VBAT_DIVIDER (0.5F)               // 150K + 150K voltage divider on VBAT
+#define VBAT_DIVIDER_COMP (2.0F)          // Compensation factor for the VBAT divider
+#else
+#define VBAT_PIN          (A7)
 #define VBAT_DIVIDER      (0.71275837F)   // 2M + 0.806M voltage divider on VBAT = (2M / (0.806M + 2M))
 #define VBAT_DIVIDER_COMP (1.403F)        // Compensation factor for the VBAT divider
+#endif
 
-int readVBAT(void) {
-  int raw;
+#define REAL_VBAT_MV_PER_LSB (VBAT_DIVIDER_COMP * VBAT_MV_PER_LSB)
+
+
+float readVBAT(void) {
+  float raw;
 
   // Set the analog reference to 3.0V (default = 3.6V)
   analogReference(AR_INTERNAL_3_0);
@@ -22,38 +33,23 @@ int readVBAT(void) {
   analogReference(AR_DEFAULT);
   analogReadResolution(10);
 
-  return raw;
+  // Convert the raw value to compensated mv, taking the resistor-
+  // divider into account (providing the actual LIPO voltage)
+  // ADC range is 0..3000mV and resolution is 12-bit (0..4095)
+  return raw * REAL_VBAT_MV_PER_LSB;
 }
 
 uint8_t mvToPercent(float mvolts) {
-    uint8_t battery_level;
-
-    if (mvolts >= 3000)
-    {
-        battery_level = 100;
-    }
-    else if (mvolts > 2900)
-    {
-        battery_level = 100 - ((3000 - mvolts) * 58) / 100;
-    }
-    else if (mvolts > 2740)
-    {
-        battery_level = 42 - ((2900 - mvolts) * 24) / 160;
-    }
-    else if (mvolts > 2440)
-    {
-        battery_level = 18 - ((2740 - mvolts) * 12) / 300;
-    }
-    else if (mvolts > 2100)
-    {
-        battery_level = 6 - ((2440 - mvolts) * 6) / 340;
-    }
-    else
-    {
-        battery_level = 0;
-    }
-
-    return battery_level;
+  if(mvolts<3300)
+    return 0;
+
+  if(mvolts <3600) {
+    mvolts -= 3300;
+    return mvolts/30;
+  }
+
+  mvolts -= 3600;
+  return 10 + (mvolts * 0.15F );  // thats mvolts /6.66666666
 }
 
 void setup() {
@@ -66,23 +62,13 @@ void setup() {
 
 void loop() {
   // Get a raw ADC reading
-  int vbat_raw = readVBAT();
+  float vbat_mv = readVBAT();
 
   // Convert from raw mv to percentage (based on LIPO chemistry)
-  uint8_t vbat_per = mvToPercent(vbat_raw * VBAT_MV_PER_LSB);
-
-  // Convert the raw value to compensated mv, taking the resistor-
-  // divider into account (providing the actual LIPO voltage)
-  // ADC range is 0..3000mV and resolution is 12-bit (0..4095),
-  // VBAT voltage divider is 2M + 0.806M, which needs to be added back
-  float vbat_mv = (float)vbat_raw * VBAT_MV_PER_LSB * VBAT_DIVIDER_COMP;
+  uint8_t vbat_per = mvToPercent(vbat_mv);
 
   // Display the results
-  Serial.print("ADC = ");
-  Serial.print(vbat_raw * VBAT_MV_PER_LSB);
-  Serial.print(" mV (");
-  Serial.print(vbat_raw);
-  Serial.print(") ");
+
   Serial.print("LIPO = ");
   Serial.print(vbat_mv);
   Serial.print(" mV (");