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Fix GC1109 FEM LNA being used for Heltec v4 RX #1249

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Fix GC1109 FEM LNA being used for Heltec v4 RX #1249

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28 changes: 19 additions & 9 deletions variants/heltec_v4/HeltecV4Board.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -7,15 +7,23 @@ void HeltecV4Board::begin() {
pinMode(PIN_ADC_CTRL, OUTPUT);
digitalWrite(PIN_ADC_CTRL, LOW); // Initially inactive

// ---- GC1109 RF FRONT END CONFIGURATION ----
// The Heltec V4 uses a GC1109 FEM chip with integrated PA and LNA
// RF switch control: PA_TX_EN LOW = RX path (LNA), HIGH = TX path (PA)

// PA_POWER: Power enable for GC1109 chip (always on)
pinMode(P_LORA_PA_POWER, OUTPUT);
digitalWrite(P_LORA_PA_POWER,HIGH);
digitalWrite(P_LORA_PA_POWER, HIGH);

// PA_EN: Main enable for GC1109 (must be HIGH for both RX and TX)
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);
digitalWrite(P_LORA_PA_EN, HIGH);

// PA_TX_EN: RF switch control (LOW=RX/LNA, HIGH=TX/PA)
pinMode(P_LORA_PA_TX_EN, OUTPUT);
digitalWrite(P_LORA_PA_TX_EN, LOW); // Default to RX mode
// -------------------------------------------

periph_power.begin();

Expand All @@ -32,13 +40,13 @@ void HeltecV4Board::begin() {
}

void HeltecV4Board::onBeforeTransmit(void) {
digitalWrite(P_LORA_TX_LED, HIGH); // turn TX LED on
digitalWrite(P_LORA_PA_TX_EN,HIGH);
digitalWrite(P_LORA_TX_LED, HIGH); // Turn TX LED on
digitalWrite(P_LORA_PA_TX_EN, HIGH); // Switch to TX path (PA)
}

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); // Switch back to RX path (LNA)
digitalWrite(P_LORA_TX_LED, LOW); // Turn TX LED off
}

void HeltecV4Board::enterDeepSleep(uint32_t secs, int pin_wake_btn) {
Expand All @@ -50,7 +58,9 @@ 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 (PA_EN=HIGH, PA_TX_EN=LOW for RX mode)
rtc_gpio_hold_en((gpio_num_t)P_LORA_PA_EN);
rtc_gpio_hold_en((gpio_num_t)P_LORA_PA_TX_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
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2 changes: 2 additions & 0 deletions variants/heltec_v4/platformio.ini
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,8 @@ build_flags =
-D SX126X_DIO3_TCXO_VOLTAGE=1.8
-D SX126X_CURRENT_LIMIT=140
-D SX126X_RX_BOOSTED_GAIN=1
-D SX126X_RXEN=RADIOLIB_NC ; No separate RX enable pin
-D SX126X_TXEN=46 ; TX enable pin (P_LORA_PA_TX_EN) controls RF switch
-D PIN_GPS_RX=38
-D PIN_GPS_TX=39
-D PIN_GPS_RESET=42
Expand Down