Fix pin mapping & TX switch (it's DIO2)

variants/rak3401/RAK3401Board.cpp

@@ -20,37 +20,27 @@ void RAK3401Board::begin() {
 
   Wire.begin();
 
+  // PIN_3V3_EN (WB_IO2, P0.34) controls the 3V3_S switched peripheral rail
+  // AND the 5V boost regulator (U5) on the RAK13302 that powers the SKY66122 PA.
+  // Must stay HIGH during radio operation — do not toggle for power saving.
   pinMode(PIN_3V3_EN, OUTPUT);
   digitalWrite(PIN_3V3_EN, HIGH);
 
-  // Initialize SKY66122-11 FEM on the RAK13302 module.
-  // CSD (P0.24) and CPS (P0.21) must be HIGH for both TX and RX modes.
-  // CTX (P0.31) selects TX(HIGH) vs RX(LOW) and also enables the 5V boost
-  // converter that powers the PA section (VCC1/VCC2).
-  // The LNA section (VSUP1/VCC0) runs on 3.3V and works with boost off.
-  //
-  // Drive CTX LOW first to prevent transient TX mode (Mode 2) while CSD/CPS
-  // are being enabled — the RAK13302 has no pull-downs on these pins.
-  pinMode(P_LORA_PA_EN, OUTPUT);
-  digitalWrite(P_LORA_PA_EN, LOW);         // CTX=0: RX mode, boost off
-
-  pinMode(P_LORA_PA_CSD, OUTPUT);
-  digitalWrite(P_LORA_PA_CSD, HIGH);       // CSD=1: enable FEM
-
+  // Enable SKY66122-11 FEM on the RAK13302 module.
+  // CSD and CPS are tied together on the RAK13302 PCB, routed to IO3 (P0.21).
+  // HIGH = FEM active (LNA for RX, PA path available for TX).
+  // TX/RX switching (CTX) is handled by SX1262 DIO2 via SetDIO2AsRfSwitchCtrl.
   pinMode(SX126X_POWER_EN, OUTPUT);
-  digitalWrite(SX126X_POWER_EN, HIGH);     // CPS=1: enable TX/RX paths
-
-  delay(1);  // SKY66122 turn-on settling time
+  digitalWrite(SX126X_POWER_EN, HIGH);
+  delay(1);  // SKY66122 turn-on settling time (tON = 3us typ)
 }
 
 #ifdef NRF52_POWER_MANAGEMENT
 void RAK3401Board::initiateShutdown(uint8_t reason) {
-  // Put SKY66122 in guaranteed <1 uA shutdown (Mode 4: CSD=0, CTX=0, CPS=0)
-  digitalWrite(P_LORA_PA_EN, LOW);         // CTX=0, boost off
-  digitalWrite(SX126X_POWER_EN, LOW);      // CPS=0
-  digitalWrite(P_LORA_PA_CSD, LOW);        // CSD=0
+  // Disable SKY66122 FEM (CSD+CPS LOW = shutdown, <1 uA)
+  digitalWrite(SX126X_POWER_EN, LOW);
 
-  // Disable 3V3 switched peripherals
+  // Disable 3V3 switched peripherals and 5V boost
   digitalWrite(PIN_3V3_EN, LOW);
 
   enterSystemOff(reason);

variants/rak3401/RAK3401Board.h

@@ -38,14 +38,6 @@ public:
     return "RAK 3401";
   }
 
-  // SKY66122 FEM TX/RX switching via CTX pin.
-  // CTX=HIGH: TX mode + 5V boost ON (PA powered from VCC1/VCC2)
-  // CTX=LOW:  RX mode + 5V boost OFF (LNA powered from VSUP1 at 3.3V)
-  void onBeforeTransmit() override {
-    digitalWrite(P_LORA_PA_EN, HIGH);  // CTX=1: TX mode, boost on
-  }
-
-  void onAfterTransmit() override {
-    digitalWrite(P_LORA_PA_EN, LOW);   // CTX=0: RX mode, boost off
-  }
+  // TX/RX switching is handled by SX1262 DIO2 -> SKY66122 CTX (hardware-timed).
+  // No onBeforeTransmit/onAfterTransmit overrides needed.
 };

variants/rak3401/variant.h

@@ -147,14 +147,15 @@ static const uint8_t AREF = PIN_AREF;
 #define SX126X_BUSY (9)
 #define SX126X_RESET (4)
 
-// SKY66122-11 FEM control pins (active HIGH, active LOW = shutdown <1uA)
-// CSD+CPS must be HIGH for TX and RX; CTX selects TX(HIGH) vs RX(LOW)
-// CTX also enables the 5V boost converter for the PA during TX
-#define P_LORA_PA_CSD (24)          // P0.24 -> SKY66122 CSD (pin 11) - FEM enable
-#define SX126X_POWER_EN (21)        // P0.21 -> SKY66122 CPS (pin 1) - path select
-#define P_LORA_PA_EN  (31)          // P0.31 -> SKY66122 CTX (pin 2) - TX/RX + boost EN
-
-// DIO2 has a NC 0R footprint (R25) to CTX; not connected by default
+// SKY66122-11 FEM control on the RAK13302 module:
+//   CSD + CPS are tied together on the PCB, routed to WisBlock IO3 (P0.21).
+//   Setting IO3 HIGH enables the FEM (LNA for RX, PA path for TX).
+//   CTX is connected to SX1262 DIO2 — the radio handles TX/RX switching
+//   in hardware via SetDIO2AsRfSwitchCtrl (microsecond-accurate, no GPIO needed).
+//   The 5V boost for the PA is enabled by WB_IO2 (P0.34 = PIN_3V3_EN).
+#define SX126X_POWER_EN (21)        // P0.21 = IO3 -> SKY66122 CSD+CPS (FEM enable)
+
+// CTX is driven by SX1262 DIO2, not a GPIO
 #define SX126X_DIO2_AS_RF_SWITCH
 #define SX126X_DIO3_TCXO_VOLTAGE 1.8