Fix misconfigured ADC and remove now unnecessary filtering

src/components/battery/BatteryController.cpp

@@ -23,7 +23,6 @@ void Battery::Update() {
     return;
   }
   // Non blocking read
-  samples = 0;
   isReading = true;
   SaadcInit();
 
@@ -40,9 +39,9 @@ void Battery::SaadcInit() {
 
   nrf_saadc_channel_config_t adcChannelConfig = {.resistor_p = NRF_SAADC_RESISTOR_DISABLED,
                                                  .resistor_n = NRF_SAADC_RESISTOR_DISABLED,
-                                                 .gain = NRF_SAADC_GAIN1_5,
+                                                 .gain = NRF_SAADC_GAIN1_4,
                                                  .reference = NRF_SAADC_REFERENCE_INTERNAL,
-                                                 .acq_time = NRF_SAADC_ACQTIME_3US,
+                                                 .acq_time = NRF_SAADC_ACQTIME_40US,
                                                  .mode = NRF_SAADC_MODE_SINGLE_ENDED,
                                                  .burst = NRF_SAADC_BURST_ENABLED,
                                                  .pin_p = batteryVoltageAdcInput,
@@ -60,22 +59,21 @@ void Battery::SaadcEventHandler(nrfx_saadc_evt_t const* p_event) {
     APP_ERROR_CHECK(nrfx_saadc_buffer_convert(&saadc_value, 1));
 
     // A hardware voltage divider divides the battery voltage by 2
-    // ADC gain is 1/5
-    // thus adc_voltage = battery_voltage / 2 * gain = battery_voltage / 10
-    // reference_voltage is 0.6V
+    // ADC gain is 1/4
+    // thus adc_voltage = battery_voltage / 2 * gain = battery_voltage / 8
+    // reference_voltage is 600mV
     // p_event->data.done.p_buffer[0] = (adc_voltage / reference_voltage) * 1024
-    voltage = p_event->data.done.p_buffer[0] * 6000 / 1024;
-    percentRemaining = (voltage - battery_min) * 100 / (battery_max - battery_min);
-    percentRemaining = std::max(percentRemaining, 0);
-    percentRemaining = std::min(percentRemaining, 100);
-    percentRemainingBuffer.Insert(percentRemaining);
-
-    samples++;
-    if (samples > percentRemainingSamples) {
-      nrfx_saadc_uninit();
-      isReading = false;
+    voltage = p_event->data.done.p_buffer[0] * (8 * 600) / 1024;
+
+    if (voltage > battery_max) {
+      percentRemaining = 100;
+    } else if (voltage < battery_min) {
+      percentRemaining = 0;
     } else {
-      nrfx_saadc_sample();
+      percentRemaining = (voltage - battery_min) * 100 / (battery_max - battery_min);
     }
+
+    nrfx_saadc_uninit();
+    isReading = false;
   }
 }

src/components/battery/BatteryController.h

@@ -7,38 +7,6 @@
 namespace Pinetime {
   namespace Controllers {
 
-    /** A simple circular buffer that can be used to average
-     out the sensor values. The total capacity of the CircBuffer
-    is given as the template parameter N.
-    */
-    template <int N> class CircBuffer {
-    public:
-      CircBuffer() : arr {}, sz {}, cap {N}, head {} {
-      }
-      /**
-     insert member function overwrites the next data to the current
-    HEAD and moves the HEAD to the newly inserted value.
-    */
-      void Insert(const uint8_t num) {
-        head %= cap;
-        arr[head++] = num;
-        if (sz != cap) {
-          sz++;
-        }
-      }
-
-      uint8_t GetAverage() const {
-        int sum = std::accumulate(arr.begin(), arr.end(), 0);
-        return static_cast<uint8_t>(sum / sz);
-      }
-
-    private:
-      std::array<uint8_t, N> arr; /**< internal array used to store the values*/
-      uint8_t sz;             /**< The current size of the array.*/
-      uint8_t cap;            /**< Total capacity of the CircBuffer.*/
-      uint8_t head;           /**< The current head of the CircBuffer*/
-    };
-
     class Battery {
     public:
       Battery();
@@ -47,10 +15,7 @@ namespace Pinetime {
       void Update();
 
       uint8_t PercentRemaining() const {
-        auto avg = percentRemainingBuffer.GetAverage();
-        avg = std::min(avg, static_cast<uint8_t>(100));
-        avg = std::max(avg, static_cast<uint8_t>(0));
-        return avg;
+        return percentRemaining;
       }
 
       uint16_t Voltage() const {
@@ -69,14 +34,11 @@ namespace Pinetime {
       static Battery* instance;
       nrf_saadc_value_t saadc_value;
 
-      static constexpr uint8_t percentRemainingSamples = 5;
-      CircBuffer<percentRemainingSamples> percentRemainingBuffer {};
-
       static constexpr uint32_t chargingPin = 12;
       static constexpr uint32_t powerPresentPin = 19;
       static constexpr nrf_saadc_input_t batteryVoltageAdcInput = NRF_SAADC_INPUT_AIN7;
       uint16_t voltage = 0;
-      int percentRemaining = -1;
+      uint8_t percentRemaining = 0;
 
       bool isCharging = false;
       bool isPowerPresent = false;
@@ -87,7 +49,6 @@ namespace Pinetime {
       static void AdcCallbackStatic(nrfx_saadc_evt_t const* event);
 
       bool isReading = false;
-      uint8_t samples = 0;
     };
   }
 }