Heltec v4 PA detection

Boards.h

@@ -399,7 +399,7 @@
       #define HAS_LORA_LNA true
       #define PIN_WAKEUP GPIO_NUM_0
       #define WAKEUP_LEVEL 0
-      #define OCP_TUNED 0x18
+      #define OCP_TUNED 0x38
       #define Vext GPIO_NUM_36
 
       const int pin_btn_usr1 = 0;
@@ -422,14 +422,17 @@
 
       #define LORA_LNA_GAIN  17
       #define LORA_LNA_GVT   12
-      #define LORA_PA_GC1109 true
+      #define LORA_PA_AUTO_DETECT true
       #define LORA_PA_PWR_EN  7
-      #define LORA_PA_CSD     2
-      #define LORA_PA_CPS    46
-
-      #define PA_MAX_OUTPUT  28
-      #define PA_GAIN_POINTS 22
-      #define PA_GAIN_VALUES 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 10, 10, 9, 9, 8, 7
+      #define LORA_PA_CSD     2  // GC1109: PA_EN | KCT8103L: CSD (same pin, different pull resistor)
+      #define LORA_PA_CTX     5  // KCT8103L: TX/LNA select (CTX=LOW=LNA, CTX=HIGH=PA)
+      #define LORA_PA_CPS    46  // GC1109: TX_EN
+
+      #define PA_MAX_OUTPUT          28
+      #define PA_GAIN_POINTS         22
+      #define PA_GC1109_GAIN_VALUES   11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 10, 10, 9, 9, 8, 7
+      #define PA_KCT8103L_GAIN_VALUES 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 12, 12, 11, 11, 10, 9, 8, 7
+      #define PA_GAIN_VALUES PA_KCT8103L_GAIN_VALUES // compile-time fallback; runtime detection selects correct table
 
       const int pin_cs = 8;
       const int pin_busy = 13;

RNode_Firmware.ino

@@ -1767,7 +1767,13 @@ void sleep_now() {
         #endif
       #endif
       #if BOARD_MODEL == BOARD_HELTEC32_V4
-          digitalWrite(LORA_PA_CPS, LOW);
+          #if LORA_PA_AUTO_DETECT
+            if (sx126x_modem.isKCT8103L()) {
+              digitalWrite(LORA_PA_CTX, LOW);
+            } else {
+              digitalWrite(LORA_PA_CPS, LOW);
+            }
+          #endif
           digitalWrite(LORA_PA_CSD, LOW);
           digitalWrite(LORA_PA_PWR_EN, LOW);
           digitalWrite(Vext, HIGH);

Utilities.h

@@ -1287,7 +1287,13 @@ int getTxPower() {
 }
 
 #if HAS_LORA_PA
-	const int tx_gain[PA_GAIN_POINTS] = {PA_GAIN_VALUES};
+  #if LORA_PA_AUTO_DETECT
+    static const int gc1109_tx_gain[PA_GAIN_POINTS]   = {PA_GC1109_GAIN_VALUES};
+    static const int kct8103l_tx_gain[PA_GAIN_POINTS] = {PA_KCT8103L_GAIN_VALUES};
+    const int* tx_gain = sx126x_modem.isKCT8103L() ? kct8103l_tx_gain : gc1109_tx_gain;
+  #else
+    const int tx_gain[PA_GAIN_POINTS] = {PA_GAIN_VALUES};
+  #endif
 #endif
 
 int map_target_power_to_modem_output(int target_tx_power) {

arduino-cli.yaml

@@ -4,4 +4,3 @@ board_manager:
   - https://raw.githubusercontent.com/RAKwireless/RAKwireless-Arduino-BSP-Index/main/package_rakwireless_index.json
   - https://github.com/HelTecAutomation/Heltec_nRF52/releases/download/1.7.0/package_heltec_nrf_index.json
   - https://adafruit.github.io/arduino-board-index/package_adafruit_index.json
-  - http://unsigned.io/arduino/package_unsignedio_UnsignedBoards_index.json

sx126x.cpp

@@ -335,39 +335,39 @@ int sx126x::begin(long frequency) {
   setFrequency(frequency);
   setTxPower(2);
   enableCrc();
-  writeRegister(REG_LNA_6X, 0x96); // Set LNA boost
+  writeRegister(REG_LNA_6X, 0x96); // Set LNA boosted gain mode
+  // Undocumented SX1262 register patch recommended by Heltec/Semtech for improved RX sensitivity.
+  writeRegister(0x08B5, readRegister(0x08B5) | 0x01);
   uint8_t basebuf[2] = {0}; // Set base addresses
   executeOpcode(OP_BUFFER_BASE_ADDR_6X, basebuf, 2);
 
   setModulationParams(_sf, _bw, _cr, _ldro);
   setPacketParams(_preambleLength, _implicitHeaderMode, _payloadLength, _crcMode);
 
   #if HAS_LORA_PA
-    #if LORA_PA_GC1109
-      // Enable Vfem_ctl for supply to
-      // PA power net.
+    #if LORA_PA_AUTO_DETECT
+      // Power up the FEM, then read GPIO LORA_PA_CSD as input.
+      // The V4.2 (GC1109) board pulls it LOW; V4.3 (KCT8103L) pulls it HIGH.
       pinMode(LORA_PA_PWR_EN, OUTPUT);
       digitalWrite(LORA_PA_PWR_EN, HIGH);
-
-      // Enable PA LNA and TX standby
-      pinMode(LORA_PA_CSD, OUTPUT);
-      digitalWrite(LORA_PA_CSD, HIGH);
-
-      // Keep PA CPS low until actual
-      // transmit. Does it save power?
-      // Who knows? Will have to measure.
-      // Note from the future: Nope.
-      // Power consumption is the same,
-      // and turning it on and off is
-      // not something that it likes.
-      // Keeping it high for now.
-      pinMode(LORA_PA_CPS, OUTPUT);
-      digitalWrite(LORA_PA_CPS, HIGH);
-
-      // On Heltec V4, the PA CTX pin
-      // is driven by the SX1262 DIO2
-      // pin directly, so we do not
-      // need to manually raise this.
+      delay(1);
+      pinMode(LORA_PA_CSD, INPUT);
+      delay(1);
+      _kct8103l = (digitalRead(LORA_PA_CSD) == HIGH);
+
+      if (_kct8103l) {
+        // KCT8103L (V4.3): CSD=HIGH enables chip, CTX=LOW=LNA/RX, CTX=HIGH=PA/TX
+        pinMode(LORA_PA_CSD, OUTPUT);
+        digitalWrite(LORA_PA_CSD, HIGH);
+        pinMode(LORA_PA_CTX, OUTPUT);
+        digitalWrite(LORA_PA_CTX, LOW); // LNA enabled by default
+      } else {
+        // GC1109 (V4.2): PA_EN=HIGH enables chip, CPS=HIGH=full PA mode
+        pinMode(LORA_PA_CSD, OUTPUT);
+        digitalWrite(LORA_PA_CSD, HIGH);
+        pinMode(LORA_PA_CPS, OUTPUT);
+        digitalWrite(LORA_PA_CPS, HIGH);
+      }
     #endif
   #endif
 
@@ -378,12 +378,12 @@ void sx126x::end() { sleep(); SPI.end(); _preinit_done = false; }
 
 int sx126x::beginPacket(int implicitHeader) {
   #if HAS_LORA_PA
-    #if LORA_PA_GC1109
-      // Enable PA CPS for transmit
-      // digitalWrite(LORA_PA_CPS, HIGH);
-      // Disabled since we're keeping it
-      // on permanently as long as the
-      // radio is powered up.
+    #if LORA_PA_AUTO_DETECT
+      if (_kct8103l) {
+        // CTX=HIGH: switch KCT8103L to PA/TX mode.
+        digitalWrite(LORA_PA_CTX, HIGH);
+      }
+      // GC1109: CPS kept HIGH permanently, no action needed.
     #endif
   #endif
 
@@ -595,14 +595,12 @@ void sx126x::onReceive(void(*callback)(int)){
 
 void sx126x::receive(int size) {
   #if HAS_LORA_PA
-    #if LORA_PA_GC1109
-      // Disable PA CPS for receive
-      // digitalWrite(LORA_PA_CPS, LOW);
-      // That turned out to be a bad idea.
-      // The LNA goes wonky if it's toggled
-      // on and off too quickly. We'll keep
-      // it on permanently, as long as the
-      // radio is powered up.
+    #if LORA_PA_AUTO_DETECT
+      if (_kct8103l) {
+        // CTX=LOW: switch KCT8103L to LNA/RX mode.
+        digitalWrite(LORA_PA_CTX, LOW);
+      }
+      // GC1109: CPS kept HIGH permanently, no action needed.
     #endif
   #endif
 

sx126x.h

@@ -97,6 +97,8 @@ class sx126x : public Stream {
 
   void dumpRegisters(Stream& out);
 
+  bool isKCT8103L() { return _kct8103l; }
+
 private:
   void explicitHeaderMode();
   void implicitHeaderMode();
@@ -137,6 +139,7 @@ class sx126x : public Stream {
   int _fifo_rx_addr_ptr;
   uint8_t _packet[255];
   bool _preinit_done;
+  bool _kct8103l;
   void (*_onReceive)(int);
 };