🔧 Fix GC1109 FEM LNA being used for Heltec v4 RX

variants/heltec_tracker_v2/HeltecTrackerV2Board.cpp

@@ -6,37 +6,52 @@ void HeltecTrackerV2Board::begin() {
     pinMode(PIN_ADC_CTRL, OUTPUT);
     digitalWrite(PIN_ADC_CTRL, LOW); // Initially inactive
 
-    pinMode(P_LORA_PA_POWER, OUTPUT);
-    digitalWrite(P_LORA_PA_POWER,HIGH);
-
-    rtc_gpio_hold_dis((gpio_num_t)P_LORA_PA_EN);
-    pinMode(P_LORA_PA_EN, OUTPUT);
-    digitalWrite(P_LORA_PA_EN,HIGH);
-    pinMode(P_LORA_PA_TX_EN, OUTPUT);
-    digitalWrite(P_LORA_PA_TX_EN,LOW);
-
-    periph_power.begin();
-
+    // Check if waking from deep sleep
     esp_reset_reason_t reason = esp_reset_reason();
     if (reason == ESP_RST_DEEPSLEEP) {
       long wakeup_source = esp_sleep_get_ext1_wakeup_status();
       if (wakeup_source & (1 << P_LORA_DIO_1)) {  // received a LoRa packet (while in deep sleep)
         startup_reason = BD_STARTUP_RX_PACKET;
       }
 
+      // Release RTC holds - pins retain their state, no need to reconfigure
       rtc_gpio_hold_dis((gpio_num_t)P_LORA_NSS);
+      rtc_gpio_hold_dis((gpio_num_t)P_LORA_PA_POWER);
+      rtc_gpio_hold_dis((gpio_num_t)P_LORA_PA_EN);
       rtc_gpio_deinit((gpio_num_t)P_LORA_DIO_1);
+    } else {
+      // Cold boot: Configure GC1109 FEM pins
+      // Control logic (from GC1109 datasheet):
+      //   Receive LNA:  CSD=1, CTX=0, CPS=X  (17dB gain, 2dB NF)
+      //   Transmit PA:  CSD=1, CTX=1, CPS=1  (full PA enabled)
+      // Pin mapping: CTX->DIO2 (auto), CSD->GPIO4, CPS->GPIO46, VFEM->GPIO7
+
+      // VFEM_Ctrl (GPIO7): Power enable for GC1109 LDO
+      pinMode(P_LORA_PA_POWER, OUTPUT);
+      digitalWrite(P_LORA_PA_POWER, HIGH);
+
+      // CSD (GPIO4): Chip enable - must be HIGH for GC1109 to work
+      pinMode(P_LORA_PA_EN, OUTPUT);
+      digitalWrite(P_LORA_PA_EN, HIGH);
     }
+
+    periph_power.begin();
+
+    // Note: GPIO46 (CPS) is a strapping pin - do NOT configure it here.
+    // TX handlers are fully responsible for GPIO46 (see onBeforeTransmit/onAfterTransmit)
   }
 
   void HeltecTrackerV2Board::onBeforeTransmit(void) {
-    digitalWrite(P_LORA_TX_LED, HIGH);   // turn TX LED on
-    digitalWrite(P_LORA_PA_TX_EN,HIGH);
+    // GPIO46 is a strapping pin - only drive it when actively transmitting
+    pinMode(P_LORA_PA_TX_EN, OUTPUT);
+    digitalWrite(P_LORA_PA_TX_EN, HIGH);   // CPS=1: Enable full PA mode
+    digitalWrite(P_LORA_TX_LED, HIGH);
   }
 
   void HeltecTrackerV2Board::onAfterTransmit(void) {
-    digitalWrite(P_LORA_TX_LED, LOW);   // turn TX LED off
-    digitalWrite(P_LORA_PA_TX_EN,LOW);
+    digitalWrite(P_LORA_PA_TX_EN, LOW);
+    pinMode(P_LORA_PA_TX_EN, INPUT);       // Release strapping pin
+    digitalWrite(P_LORA_TX_LED, LOW);
   }
 
   void HeltecTrackerV2Board::enterDeepSleep(uint32_t secs, int pin_wake_btn) {
@@ -48,7 +63,11 @@ void HeltecTrackerV2Board::begin() {
 
     rtc_gpio_hold_en((gpio_num_t)P_LORA_NSS);
 
-    rtc_gpio_hold_en((gpio_num_t)P_LORA_PA_EN); //It also needs to be enabled in receive mode
+    // Hold GC1109 FEM pins during sleep for RX wake capability
+    // State: CSD=1, CTX=0 (DIO2), CPS=X -> Receive LNA mode
+    rtc_gpio_hold_en((gpio_num_t)P_LORA_PA_POWER);   // VFEM_Ctrl - keep LDO powered
+    rtc_gpio_hold_en((gpio_num_t)P_LORA_PA_EN);      // CSD=1 - chip enabled
+    // Note: GPIO46 (CPS) is NOT an RTC GPIO, cannot hold - but CPS is don't care for RX
 
     if (pin_wake_btn < 0) {
       esp_sleep_enable_ext1_wakeup( (1L << P_LORA_DIO_1), ESP_EXT1_WAKEUP_ANY_HIGH);  // wake up on: recv LoRa packet

variants/heltec_tracker_v2/platformio.ini

@@ -17,15 +17,17 @@ build_flags =
   -D P_LORA_SCLK=9
   -D P_LORA_MISO=11
   -D P_LORA_MOSI=10
-  -D P_LORA_PA_POWER=7 ;power en
-  -D P_LORA_PA_EN=4
-  -D P_LORA_PA_TX_EN=46  ;enable tx
-  -D LORA_TX_POWER=10 ;If it is configured as 10 here, the final output will be 22 dbm.
-  -D MAX_LORA_TX_POWER=22 ;Max SX1262 output
+  -D P_LORA_PA_POWER=7   ; VFEM_Ctrl - GC1109 LDO power enable
+  -D P_LORA_PA_EN=4      ; CSD - GC1109 chip enable (HIGH=on)
+  -D P_LORA_PA_TX_EN=46  ; CPS - GC1109 PA mode (HIGH=full PA, LOW=bypass)
+  -D LORA_TX_POWER=10    ; 10dBm + 11dB gain = ~21dBm output (see gain curve above)
+  -D MAX_LORA_TX_POWER=22 ; Max SX1262 output -> ~28dBm at antenna
   -D SX126X_DIO2_AS_RF_SWITCH=true
   -D SX126X_DIO3_TCXO_VOLTAGE=1.8
   -D SX126X_CURRENT_LIMIT=140
   -D SX126X_RX_BOOSTED_GAIN=1
+  ; GC1109 FEM: TX/RX switching is handled by DIO2 -> CTX pin (via SX126X_DIO2_AS_RF_SWITCH)
+  ; GPIO46 is CPS (PA mode), not TX control - do not use for RF switching
   -D PIN_BOARD_SDA=5
   -D PIN_BOARD_SCL=6
   -D PIN_USER_BTN=0

variants/heltec_v4/HeltecV4Board.cpp

@@ -3,42 +3,55 @@
 void HeltecV4Board::begin() {
     ESP32Board::begin();
 
-
     pinMode(PIN_ADC_CTRL, OUTPUT);
     digitalWrite(PIN_ADC_CTRL, LOW); // Initially inactive
 
-    pinMode(P_LORA_PA_POWER, OUTPUT);
-    digitalWrite(P_LORA_PA_POWER,HIGH);
-
-    rtc_gpio_hold_dis((gpio_num_t)P_LORA_PA_EN);
-    pinMode(P_LORA_PA_EN, OUTPUT);
-    digitalWrite(P_LORA_PA_EN,HIGH);
-    pinMode(P_LORA_PA_TX_EN, OUTPUT);
-    digitalWrite(P_LORA_PA_TX_EN,LOW);
-
-
-    periph_power.begin();
-
+    // Check if waking from deep sleep
     esp_reset_reason_t reason = esp_reset_reason();
     if (reason == ESP_RST_DEEPSLEEP) {
       long wakeup_source = esp_sleep_get_ext1_wakeup_status();
       if (wakeup_source & (1 << P_LORA_DIO_1)) {  // received a LoRa packet (while in deep sleep)
         startup_reason = BD_STARTUP_RX_PACKET;
       }
 
+      // Release RTC holds - pins retain their state, no need to reconfigure
       rtc_gpio_hold_dis((gpio_num_t)P_LORA_NSS);
+      rtc_gpio_hold_dis((gpio_num_t)P_LORA_PA_POWER);
+      rtc_gpio_hold_dis((gpio_num_t)P_LORA_PA_EN);
       rtc_gpio_deinit((gpio_num_t)P_LORA_DIO_1);
+    } else {
+      // Cold boot: Configure GC1109 FEM pins
+      // Control logic (from GC1109 datasheet):
+      //   Receive LNA:  CSD=1, CTX=0, CPS=X  (17dB gain, 2dB NF)
+      //   Transmit PA:  CSD=1, CTX=1, CPS=1  (full PA enabled)
+      // Pin mapping: CTX->DIO2 (auto), CSD->GPIO2, CPS->GPIO46, VFEM->GPIO7
+
+      // VFEM_Ctrl (GPIO7): Power enable for GC1109 LDO
+      pinMode(P_LORA_PA_POWER, OUTPUT);
+      digitalWrite(P_LORA_PA_POWER, HIGH);
+
+      // CSD (GPIO2): Chip enable - must be HIGH for GC1109 to work
+      pinMode(P_LORA_PA_EN, OUTPUT);
+      digitalWrite(P_LORA_PA_EN, HIGH);
     }
+
+    periph_power.begin();
+
+    // Note: GPIO46 (CPS) is a strapping pin - do NOT configure it here.
+    // TX handlers are fully responsible for GPIO46 (see onBeforeTransmit/onAfterTransmit)
   }
 
   void HeltecV4Board::onBeforeTransmit(void) {
-    digitalWrite(P_LORA_TX_LED, HIGH);   // turn TX LED on
-    digitalWrite(P_LORA_PA_TX_EN,HIGH);
+    // GPIO46 is a strapping pin - only drive it when actively transmitting
+    pinMode(P_LORA_PA_TX_EN, OUTPUT);
+    digitalWrite(P_LORA_PA_TX_EN, HIGH);   // CPS=1: Enable full PA mode
+    digitalWrite(P_LORA_TX_LED, HIGH);
   }
 
   void HeltecV4Board::onAfterTransmit(void) {
-    digitalWrite(P_LORA_TX_LED, LOW);   // turn TX LED off
-    digitalWrite(P_LORA_PA_TX_EN,LOW);
+    digitalWrite(P_LORA_PA_TX_EN, LOW);
+    pinMode(P_LORA_PA_TX_EN, INPUT);       // Release strapping pin
+    digitalWrite(P_LORA_TX_LED, LOW);
   }
 
   void HeltecV4Board::enterDeepSleep(uint32_t secs, int pin_wake_btn) {
@@ -50,7 +63,11 @@ void HeltecV4Board::begin() {
 
     rtc_gpio_hold_en((gpio_num_t)P_LORA_NSS);
 
-    rtc_gpio_hold_en((gpio_num_t)P_LORA_PA_EN); //It also needs to be enabled in receive mode
+    // Hold GC1109 FEM pins during sleep for RX wake capability
+    // State: CSD=1, CTX=0 (DIO2), CPS=X -> Receive LNA mode
+    rtc_gpio_hold_en((gpio_num_t)P_LORA_PA_POWER);   // VFEM_Ctrl - keep LDO powered
+    rtc_gpio_hold_en((gpio_num_t)P_LORA_PA_EN);      // CSD=1 - chip enabled
+    // Note: GPIO46 (CPS) is NOT an RTC GPIO, cannot hold - but CPS is don't care for RX
 
     if (pin_wake_btn < 0) {
       esp_sleep_enable_ext1_wakeup( (1L << P_LORA_DIO_1), ESP_EXT1_WAKEUP_ANY_HIGH);  // wake up on: recv LoRa packet

variants/heltec_v4/platformio.ini

@@ -17,9 +17,9 @@ build_flags =
   -D P_LORA_SCLK=9
   -D P_LORA_MISO=11
   -D P_LORA_MOSI=10
-  -D P_LORA_PA_POWER=7   ;power en
-  -D P_LORA_PA_EN=2
-  -D P_LORA_PA_TX_EN=46  ;enable tx
+  -D P_LORA_PA_POWER=7   ; VFEM_Ctrl - GC1109 LDO power enable
+  -D P_LORA_PA_EN=2      ; CSD - GC1109 chip enable (HIGH=on)
+  -D P_LORA_PA_TX_EN=46  ; CPS - GC1109 PA mode (HIGH=full PA, LOW=bypass)
   -D PIN_BOARD_SDA=17
   -D PIN_BOARD_SCL=18
   -D PIN_USER_BTN=0
@@ -31,6 +31,8 @@ build_flags =
   -D SX126X_DIO3_TCXO_VOLTAGE=1.8
   -D SX126X_CURRENT_LIMIT=140
   -D SX126X_RX_BOOSTED_GAIN=1
+  ; GC1109 FEM: TX/RX switching is handled by DIO2 -> CTX pin (via SX126X_DIO2_AS_RF_SWITCH)
+  ; GPIO46 is CPS (power save), not TX control - do not use for RF switching
   -D PIN_GPS_RX=38
   -D PIN_GPS_TX=39
   -D PIN_GPS_RESET=42