Implement proper shutdown procedure for R1 neo

fixes #2361

variants/muziworks_r1_neo/R1NeoBoard.cpp

@@ -14,9 +14,12 @@ const PowerMgtConfig power_config = {
 
 void R1NeoBoard::initiateShutdown(uint8_t reason) {
   // Disable LoRa module power before shutdown
-  MESH_DEBUG_PRINTLN("R1Neo: shutting down");
   digitalWrite(SX126X_POWER_EN, LOW);
 
+  // Signal IO controller that MCU is off, then release DCDC latch
+  digitalWrite(PIN_SOFT_SHUTDOWN, LOW);
+  digitalWrite(PIN_DCDC_EN_MCU_HOLD, LOW);
+
   if (reason == SHUTDOWN_REASON_LOW_VOLTAGE ||
       reason == SHUTDOWN_REASON_BOOT_PROTECT) {
     configureVoltageWake(power_config.lpcomp_ain_channel, power_config.lpcomp_refsel);

variants/muziworks_r1_neo/R1NeoBoard.h

@@ -18,6 +18,12 @@ public:
   R1NeoBoard() : NRF52Board("R1NEO_OTA") {}
   void begin();
 
+#ifdef NRF52_POWER_MANAGEMENT
+  void powerOff() override {
+    initiateShutdown(SHUTDOWN_REASON_USER);
+  }
+#endif
+
 #if defined(P_LORA_TX_LED)
   void onBeforeTransmit() override {
     digitalWrite(P_LORA_TX_LED, HIGH);   // turn TX LED on