Low battery warning

src/components/battery/BatteryController.cpp

@@ -86,10 +86,20 @@ void Battery::SaadcEventHandler(nrfx_saadc_evt_t const* p_event) {
       newPercent = std::min(aprox.GetValue(voltage), isCharging ? uint8_t {99} : uint8_t {100});
     }
 
+    if (isPowerPresent) {
+      batteryLowNotified = false;
+    }
+
     if ((isPowerPresent && newPercent > percentRemaining) || (!isPowerPresent && newPercent < percentRemaining) || firstMeasurement) {
       firstMeasurement = false;
       percentRemaining = newPercent;
       systemTask->PushMessage(System::Messages::BatteryPercentageUpdated);
+
+      // warn about low battery when not charging and below threshold
+      if (BatteryIsLow() && !isPowerPresent && !batteryLowNotified) {
+        systemTask->PushMessage(System::Messages::LowBattery);
+        batteryLowNotified = true;
+      }
     }
 
     nrfx_saadc_uninit();

src/components/battery/BatteryController.h

@@ -17,6 +17,9 @@ namespace Pinetime {
       uint8_t PercentRemaining() const {
         return percentRemaining;
       }
+      bool BatteryIsLow() const {
+        return percentRemaining <= lowBatteryThreshold;
+      }
 
       uint16_t Voltage() const {
         return voltage;
@@ -39,6 +42,7 @@ namespace Pinetime {
       static constexpr nrf_saadc_input_t batteryVoltageAdcInput = NRF_SAADC_INPUT_AIN7;
       uint16_t voltage = 0;
       uint8_t percentRemaining = 0;
+      bool batteryLowNotified = false;
 
       bool isFull = false;
       bool isCharging = false;
@@ -50,6 +54,8 @@ namespace Pinetime {
       void SaadcEventHandler(nrfx_saadc_evt_t const* p_event);
       static void AdcCallbackStatic(nrfx_saadc_evt_t const* event);
 
+      static constexpr uint8_t lowBatteryThreshold {15};
+
       bool isReading = false;
 
       Pinetime::System::SystemTask* systemTask = nullptr;

src/displayapp/screens/BatteryInfo.cpp

@@ -59,7 +59,7 @@ void BatteryInfo::Refresh() {
   } else if (batteryPercent == 100) {
     lv_obj_set_style_local_bg_color(charging_bar, LV_BAR_PART_INDIC, LV_STATE_DEFAULT, LV_COLOR_BLUE);
     lv_label_set_text_static(status, "Fully charged");
-  } else if (batteryPercent < 10) {
+  } else if (batteryController.BatteryIsLow()) {
     lv_obj_set_style_local_bg_color(charging_bar, LV_BAR_PART_INDIC, LV_STATE_DEFAULT, LV_COLOR_YELLOW);
     lv_label_set_text_static(status, "Battery low");
   } else {

src/systemtask/Messages.h

@@ -29,6 +29,7 @@ namespace Pinetime {
       StopRinging,
       MeasureBatteryTimerExpired,
       BatteryPercentageUpdated,
+      LowBattery,
       StartFileTransfer,
       StopFileTransfer,
       BleRadioEnableToggle

src/systemtask/SystemTask.cpp

@@ -18,6 +18,8 @@
 #include "BootErrors.h"
 
 #include <memory>
+#include <algorithm>
+#include <cstring>
 
 using namespace Pinetime::System;
 
@@ -424,6 +426,16 @@ void SystemTask::Work() {
         case Messages::BatteryPercentageUpdated:
           nimbleController.NotifyBatteryLevel(batteryController.PercentRemaining());
           break;
+        case Messages::LowBattery: {
+          Pinetime::Controllers::NotificationManager::Notification notif;
+          constexpr char message[] = "Low Battery\0Charge your watch to prevent data loss.\0";
+          constexpr size_t messageSize = std::min(sizeof(message), Pinetime::Controllers::NotificationManager::MaximumMessageSize());
+          std::memcpy(notif.message.data(), message, messageSize);
+          notif.size = messageSize;
+          notif.category = Pinetime::Controllers::NotificationManager::Categories::SimpleAlert;
+          notificationManager.Push(std::move(notif));
+          PushMessage(Messages::OnNewNotification);
+        } break;
         case Messages::OnPairing:
           if (state == SystemTaskState::Sleeping) {
             GoToRunning();