Fix RAK4631 hang when I2C WisBlock modules are present

examples/companion_radio/main.cpp

@@ -218,6 +218,11 @@ void setup() {
 #endif
 
 #ifdef DISPLAY_CLASS
+#ifdef RAK_BOARD
+  // sensors.begin() GPS probe may power-cycle 3V3_S rail (via WB_IO2),
+  // which resets the SSD1306. Re-init the display before starting UI.
+  if (disp) display.begin();
+#endif
   ui_task.begin(disp, &sensors, the_mesh.getNodePrefs());  // still want to pass this in as dependency, as prefs might be moved
 #endif
 }

src/helpers/ArduinoSerialInterface.h

@@ -14,11 +14,8 @@ class ArduinoSerialInterface : public BaseSerialInterface {
 public:
   ArduinoSerialInterface() { _isEnabled = false; _state = 0; }
 
-  void begin(Stream& serial) { 
-    _serial = &serial; 
-  #ifdef RAK_4631
-    pinMode(WB_IO2, OUTPUT);
-  #endif  
+  void begin(Stream& serial) {
+    _serial = &serial;
   }
 
   // BaseSerialInterface methods

src/helpers/sensors/EnvironmentSensorManager.cpp

@@ -655,7 +655,14 @@ void EnvironmentSensorManager::rakGPSInit(){
   //  MESH_DEBUG_PRINTLN("RAK base board is RAK19007/10");
   //  MESH_DEBUG_PRINTLN("GPS is installed on Socket A");
   }
-  else if(gpsIsAwake(WB_IO4)){
+
+  // WB_IO2 controls the 3V3_S switched peripheral rail on RAK these boards.
+  // gpsIsAwake() leaves the pin as INPUT on failure, killing the rail.
+  // Restore it now, before probing other sockets.
+  pinMode(WB_IO2, OUTPUT);
+  digitalWrite(WB_IO2, HIGH);
+
+  if(gpsIsAwake(WB_IO4)){
   //  MESH_DEBUG_PRINTLN("RAK base board is RAK19003/9");
   //  MESH_DEBUG_PRINTLN("GPS is installed on Socket C");
   }

variants/rak4631/RAK4631Board.cpp

@@ -16,6 +16,9 @@ void RAK4631Board::initiateShutdown(uint8_t reason) {
   // Disable LoRa module power before shutdown
   digitalWrite(SX126X_POWER_EN, LOW);
 
+  // Disable 3V3 switched peripherals
+  digitalWrite(PIN_3V3_EN, LOW);
+
   if (reason == SHUTDOWN_REASON_LOW_VOLTAGE ||
       reason == SHUTDOWN_REASON_BOOT_PROTECT) {
     configureVoltageWake(power_config.lpcomp_ain_channel, power_config.lpcomp_refsel);

variants/rak4631/variant.cpp

@@ -44,6 +44,9 @@ void initVariant()
   ledOff(PIN_LED1);
 
   pinMode(PIN_LED2, OUTPUT);
-  ledOff(PIN_LED2);;
-}
+  ledOff(PIN_LED2);
 
+  // 3V3 Power Rail
+  pinMode(PIN_3V3_EN, OUTPUT);
+  digitalWrite(PIN_3V3_EN, HIGH);
+}

variants/rak4631/variant.h

@@ -59,6 +59,8 @@ extern "C"
 	static const uint8_t WB_SPI_MISO = 29; // IO_SLOT
 	static const uint8_t WB_SPI_MOSI = 30; // IO_SLOT
 
+#define PIN_3V3_EN WB_IO2                  // 3V3_S switched peripheral rail control
+
 // Number of pins defined in PinDescription array
 #define PINS_COUNT (48)
 #define NUM_DIGITAL_PINS (48)