Deduplicate DC/DC regulator enable for NRF52 boards

Some NRF52 boards are able to use the internal power-efficient DC/DC
regulator. Add a new class that can be inherited by board classes to
enable this feature and reduce the power consumption.

Signed-off-by: Frieder Schrempf <frieder@fris.de>

src/helpers/NRF52Board.cpp

@@ -1,6 +1,23 @@
 #if defined(NRF52_PLATFORM)
 #include "NRF52Board.h"
 
+void NRF52Board::begin() {
+  startup_reason = BD_STARTUP_NORMAL;
+}
+
+void NRF52BoardDCDC::begin() {
+  NRF52Board::begin();
+
+  // Enable DC/DC converter for improved power efficiency
+  uint8_t sd_enabled = 0;
+  sd_softdevice_is_enabled(&sd_enabled);
+  if (sd_enabled) {
+    sd_power_dcdc_mode_set(NRF_POWER_DCDC_ENABLE);
+  } else {
+    NRF_POWER->DCDCEN = 1;
+  }
+}
+
 // Temperature from NRF52 MCU
 float NRF52Board::getMCUTemperature() {
   NRF_TEMP->TASKS_START = 1; // Start temperature measurement

src/helpers/NRF52Board.h

@@ -10,9 +10,21 @@ protected:
   uint8_t startup_reason;
 
 public:
-  virtual void begin() { startup_reason = BD_STARTUP_NORMAL; }
+  virtual void begin();
   virtual uint8_t getStartupReason() const override { return startup_reason; }
   float getMCUTemperature() override;
   virtual void reboot() override { NVIC_SystemReset(); }
 };
+
+/*
+ * The NRF52 has an internal DC/DC regulator that allows increased efficiency
+ * compared to the LDO regulator. For being able to use it, the module/board
+ * needs to have the required inductors and and capacitors populated. If the
+ * hardware requirements are met, this subclass can be used to enable the DC/DC
+ * regulator.
+ */
+class NRF52BoardDCDC : virtual public NRF52Board {
+public:
+  virtual void begin() override;
+};
 #endif