Hold GC1109 PA_POWER during deep sleep for LNA RX wake

The GC1109 FEM needs its VFEM_Ctrl pin held HIGH during deep sleep
to keep the LNA active, enabling proper RX sensitivity for
wake-on-packet. Without this, the LNA is unpowered during sleep
and RX wake sensitivity is degraded by ~17dB.

Release RTC holds in begin() after configuring GPIO registers
(not before) to ensure glitch-free pin transitions on wake.

Trade-off: ~6.5mA additional sleep current for significantly
improved wake-on-packet range.

Author: weebl2000

variants/heltec_tracker_v2/HeltecTrackerV2Board.cpp

@@ -6,12 +6,17 @@ void HeltecTrackerV2Board::begin() {
     pinMode(PIN_ADC_CTRL, OUTPUT);
     digitalWrite(PIN_ADC_CTRL, LOW); // Initially inactive
 
+    // Set up digital GPIO registers before releasing RTC hold. The hold latches
+    // the pad state including function select, so register writes accumulate
+    // without affecting the pad. On hold release, all changes apply atomically
+    // (IO MUX switches to digital GPIO with output already HIGH — no glitch).
     pinMode(P_LORA_PA_POWER, OUTPUT);
     digitalWrite(P_LORA_PA_POWER,HIGH);
+    rtc_gpio_hold_dis((gpio_num_t)P_LORA_PA_POWER);
 
-    rtc_gpio_hold_dis((gpio_num_t)P_LORA_PA_EN);
     pinMode(P_LORA_PA_EN, OUTPUT);
     digitalWrite(P_LORA_PA_EN,HIGH);
+    rtc_gpio_hold_dis((gpio_num_t)P_LORA_PA_EN);
     pinMode(P_LORA_PA_TX_EN, OUTPUT);
     digitalWrite(P_LORA_PA_TX_EN,LOW);
 
@@ -48,7 +53,9 @@ 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 to keep LNA active for RX wake
+    rtc_gpio_hold_en((gpio_num_t)P_LORA_PA_POWER);
+    rtc_gpio_hold_en((gpio_num_t)P_LORA_PA_EN);
 
     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

@@ -17,11 +17,11 @@ 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 GC1109 gain = ~21dBm output
+  -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

variants/heltec_v4/HeltecV4Board.cpp

@@ -7,12 +7,17 @@ void HeltecV4Board::begin() {
     pinMode(PIN_ADC_CTRL, OUTPUT);
     digitalWrite(PIN_ADC_CTRL, LOW); // Initially inactive
 
+    // Set up digital GPIO registers before releasing RTC hold. The hold latches
+    // the pad state including function select, so register writes accumulate
+    // without affecting the pad. On hold release, all changes apply atomically
+    // (IO MUX switches to digital GPIO with output already HIGH — no glitch).
     pinMode(P_LORA_PA_POWER, OUTPUT);
     digitalWrite(P_LORA_PA_POWER,HIGH);
+    rtc_gpio_hold_dis((gpio_num_t)P_LORA_PA_POWER);
 
-    rtc_gpio_hold_dis((gpio_num_t)P_LORA_PA_EN);
     pinMode(P_LORA_PA_EN, OUTPUT);
     digitalWrite(P_LORA_PA_EN,HIGH);
+    rtc_gpio_hold_dis((gpio_num_t)P_LORA_PA_EN);
     pinMode(P_LORA_PA_TX_EN, OUTPUT);
     digitalWrite(P_LORA_PA_TX_EN,LOW);
 
@@ -50,7 +55,9 @@ 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 to keep LNA active for RX wake
+    rtc_gpio_hold_en((gpio_num_t)P_LORA_PA_POWER);
+    rtc_gpio_hold_en((gpio_num_t)P_LORA_PA_EN);
 
     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