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

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This commit is contained in:
Wessel Nieboer
2026-02-27 11:30:46 +01:00
parent 5a5568ed56
commit 49d8313501
3 changed files with 22 additions and 39 deletions
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34
variants/rak3401/RAK3401Board.cpp
View File

@@ -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);

12
variants/rak3401/RAK3401Board.h
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@@ -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.
};

15
variants/rak3401/variant.h
View File

@@ -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
// 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)
// DIO2 has a NC 0R footprint (R25) to CTX; not connected by default
// CTX is driven by SX1262 DIO2, not a GPIO
#define SX126X_DIO2_AS_RF_SWITCH
#define SX126X_DIO3_TCXO_VOLTAGE 1.8