add power off to nano g2

variants/nano_g2_ultra/nano-g2.h

@@ -1,7 +1,9 @@
 #pragma once
 
-#include <MeshCore.h>
+#include "variant.h"
+
 #include <Arduino.h>
+#include <MeshCore.h>
 
 // LoRa radio module pins
 #define P_LORA_DIO_1             (32 + 10)
@@ -32,8 +34,7 @@
 #define PIN_VBAT_READ            (0 + 2)
 #define REAL_VBAT_MV_PER_LSB     (VBAT_DIVIDER_COMP * VBAT_MV_PER_LSB)
 
-class NanoG2Ultra : public mesh::MainBoard
-{
+class NanoG2Ultra : public mesh::MainBoard {
 protected:
   uint8_t startup_reason;
 
@@ -42,18 +43,21 @@ public:
   uint16_t getBattMilliVolts() override;
   bool startOTAUpdate(const char *id, char reply[]) override;
 
-  uint8_t getStartupReason() const override
-  {
-    return startup_reason;
-  }
+  uint8_t getStartupReason() const override { return startup_reason; }
 
-  const char *getManufacturerName() const override
-  {
-    return "Nano G2 Ultra";
-  }
+  const char *getManufacturerName() const override { return "Nano G2 Ultra"; }
+
+  void reboot() override { NVIC_SystemReset(); }
+
+  void powerOff() override {
+    // put GPS chip to sleep
+    digitalWrite(PIN_GPS_STANDBY, LOW);
+// unset buzzer to prevent notification circuit activating on hibernate
+#undef PIN_BUZZER
+
+    nrf_gpio_cfg_sense_input(digitalPinToInterrupt(PIN_USER_BTN), NRF_GPIO_PIN_NOPULL,
+                             NRF_GPIO_PIN_SENSE_LOW);
 
-  void reboot() override
-  {
-    NVIC_SystemReset();
+    sd_power_system_off();
   }
 };