Fix M5Stack Unit C6L: RX, flash size, pin conflicts

- Initialize PI4IOE5V6408 I2C GPIO expander for RF switch/LNA control
- Fix I2C bus pins (SDA=10, SCL=8) - ESP32-C6 only has one I2C peripheral
- Remove SX126X_RXEN=5 (RF switch is on expander, not ESP32 GPIO)
- Set flash size to 16MB (actual hardware, was defaulting to 4MB)
- Remove P_LORA_TX_LED=15 (GPIO15 is OLED reset, not TX LED)
- Fix TCXO voltage 1.8V -> 3.0V
- Remove unused GPS_RX/GPS_TX defines
- Add esp_mac.h include for ESP32-C6 BLE builds
- Add WiFi companion radio build target

src/helpers/esp32/SerialBLEInterface.cpp

@@ -1,3 +1,4 @@
+#include <esp_mac.h>
 #include "SerialBLEInterface.h"
 #include "esp_mac.h"
 

variants/m5stack_unit_c6l/UnitC6LBoard.h

@@ -1,15 +1,111 @@
+
 #pragma once
 
 #include <Arduino.h>
+#include <Wire.h>
 #include <helpers/ESP32Board.h>
 
+// PI4IOE5V6408 I2C GPIO expander - controls RF switch, LNA, and LoRa reset
+// Sits on the internal I2C bus (SDA=10, SCL=8), which is configured as
+// the primary Wire bus via PIN_BOARD_SDA/SCL in platformio.ini.
+// ESP32-C6 only has ONE I2C hardware peripheral - do NOT use TwoWire(1).
+
+#define PI4IO_ADDR            0x43
+#define PI4IO_REG_CHIP_RESET  0x01
+#define PI4IO_REG_IO_DIR      0x03
+#define PI4IO_REG_OUT_SET     0x05
+#define PI4IO_REG_OUT_H_IM    0x07
+#define PI4IO_REG_IN_DEF_STA  0x09
+#define PI4IO_REG_PULL_EN     0x0B
+#define PI4IO_REG_PULL_SEL    0x0D
+#define PI4IO_REG_INT_MASK    0x11
+#define PI4IO_REG_IRQ_STA     0x13
+
 class UnitC6LBoard : public ESP32Board {
 public:
   void begin() {
-    ESP32Board::begin();
+    ESP32Board::begin();  // This calls Wire.begin(10, 8) via PIN_BOARD_SDA/SCL
+    initGPIOExpander();
   }
 
   const char* getManufacturerName() const override {
     return "Unit C6L";
   }
+
+private:
+  void i2cWrite(uint8_t reg, uint8_t value) {
+    Wire.beginTransmission(PI4IO_ADDR);
+    Wire.write(reg);
+    Wire.write(value);
+    Wire.endTransmission();
+  }
+
+  uint8_t i2cRead(uint8_t reg) {
+    Wire.beginTransmission(PI4IO_ADDR);
+    Wire.write(reg);
+    Wire.endTransmission();
+    Wire.requestFrom((uint8_t)PI4IO_ADDR, (uint8_t)1);
+    return Wire.read();
+  }
+
+  bool i2cProbe() {
+    Wire.beginTransmission(PI4IO_ADDR);
+    return Wire.endTransmission() == 0;
+  }
+
+  void initGPIOExpander() {
+    // Matches Meshtastic's c6l_init() in variant.cpp
+    // Uses Wire (already on SDA=10, SCL=8 from ESP32Board::begin)
+
+    if (!i2cProbe()) {
+      Serial.printf("C6L: ERROR - PI4IOE5V6408 not found at 0x%02X\n", PI4IO_ADDR);
+      return;
+    }
+    Serial.println("C6L: PI4IOE5V6408 found, initializing...");
+
+    // Reset expander
+    i2cWrite(PI4IO_REG_CHIP_RESET, 0xFF);
+    delay(10);
+    i2cRead(PI4IO_REG_CHIP_RESET);
+    delay(10);
+
+    // P6 (RF switch) and P7 (LoRa reset) as outputs
+    i2cWrite(PI4IO_REG_IO_DIR, 0b11000000);
+    delay(10);
+
+    // Disable high-impedance on P2-P5
+    i2cWrite(PI4IO_REG_OUT_H_IM, 0b00111100);
+    delay(10);
+
+    // Pull-up on P0, P1, P6, P7; pull-down on others
+    i2cWrite(PI4IO_REG_PULL_SEL, 0b11000011);
+    delay(10);
+    i2cWrite(PI4IO_REG_PULL_EN, 0b11000011);
+    delay(10);
+
+    // Button defaults (P0, P1 default HIGH - active low buttons)
+    i2cWrite(PI4IO_REG_IN_DEF_STA, 0b00000011);
+    delay(10);
+
+    // Interrupt mask: only P0, P1 generate interrupts
+    i2cWrite(PI4IO_REG_INT_MASK, 0b11111100);
+    delay(10);
+
+    // Set P7 HIGH (LoRa out of reset)
+    i2cWrite(PI4IO_REG_OUT_SET, 0b10000000);
+    delay(10);
+
+    // Clear pending IRQ
+    i2cRead(PI4IO_REG_IRQ_STA);
+
+    // Set P6 HIGH (RF switch -> routes antenna to LoRa)
+    uint8_t out = i2cRead(PI4IO_REG_OUT_SET);
+    out |= (1 << 6);
+    i2cWrite(PI4IO_REG_OUT_SET, out);
+
+    // Verify
+    uint8_t verify = i2cRead(PI4IO_REG_OUT_SET);
+    Serial.printf("C6L: OUT_SET=0x%02X (expect 0xC0: P6=RF_SW, P7=LORA_RST)\n", verify);
+    Serial.printf("C6L: IO_DIR=0x%02X (expect 0xC0: P6,P7 outputs)\n", i2cRead(PI4IO_REG_IO_DIR));
+  }
 };

variants/m5stack_unit_c6l/platformio.ini

@@ -1,12 +1,15 @@
 [M5Stack_Unit_C6L]
 extends = esp32c6_base
 board = esp32-c6-devkitm-1
+board_upload.flash_size = 16MB
+board_build.flash_size = 16MB
 board_build.partitions = min_spiffs.csv ; get around 4mb flash limit
 build_flags =
   ${esp32c6_base.build_flags}
   ${sensor_base.build_flags}
   -I variants/m5stack_unit_c6l
-  -D P_LORA_TX_LED=15
+  ; P_LORA_TX_LED removed - GPIO15 is SSD1306 OLED reset pin, not a TX LED
+  ; (C6L has WS2812C RGB LED on GPIO2, no discrete TX LED)
   -D P_LORA_SCLK=20
   -D P_LORA_MISO=22
   -D P_LORA_MOSI=21
@@ -15,19 +18,19 @@ build_flags =
   -D P_LORA_BUSY=19
   -D P_LORA_RESET=-1
   -D PIN_BUZZER=11
-  -D PIN_BOARD_SDA=16
-  -D PIN_BOARD_SCL=17
-  -D SX126X_RXEN=5
+  ; I2C bus: primary bus goes to PI4IOE5V6408 GPIO expander (internal)
+  ; ESP32-C6 only has ONE I2C hardware peripheral, so Wire must be on these pins.
+  -D PIN_BOARD_SDA=10
+  -D PIN_BOARD_SCL=8
+  ; SX126X_RXEN removed - RF switch is on I2C expander (PI4IOE5V6408), not ESP32 GPIO
   -D SX126X_DIO2_AS_RF_SWITCH=true
-  -D SX126X_DIO3_TCXO_VOLTAGE=1.8
+  -D SX126X_DIO3_TCXO_VOLTAGE=3.0
   -D SX126X_CURRENT_LIMIT=140
   -D SX126X_RX_BOOSTED_GAIN=1
   -D RADIO_CLASS=CustomSX1262
   -D WRAPPER_CLASS=CustomSX1262Wrapper
   -D LORA_TX_POWER=22
   -D DISABLE_WIFI_OTA=1
-  -D GPS_RX=4
-  -D GPS_TX=5
 build_src_filter = ${esp32c6_base.build_src_filter}
   +<../variants/m5stack_unit_c6l>
   +<UnitC6LBoard.cpp>
@@ -88,6 +91,26 @@ lib_deps =
   densaugeo/base64 @ ~1.4.0
   end2endzone/NonBlockingRTTTL@^1.3.0
 
+[env:M5Stack_Unit_C6L_companion_radio_wifi]
+extends = M5Stack_Unit_C6L
+build_flags = ${M5Stack_Unit_C6L.build_flags}
+  -D MAX_CONTACTS=350
+  -D MAX_GROUP_CHANNELS=40
+  -D WIFI_DEBUG_LOGGING=1
+  -D WIFI_SSID='"myssid"'
+  -D WIFI_PWD='"mypwd"'
+  -D OFFLINE_QUEUE_SIZE=256
+;  -D MESH_PACKET_LOGGING=1
+;  -D MESH_DEBUG=1
+build_src_filter = ${M5Stack_Unit_C6L.build_src_filter}
+  +<helpers/esp32/*.cpp>
+  -<helpers/esp32/ESPNOWRadio.cpp>
+  +<../examples/companion_radio/*.cpp>
+lib_deps =
+  ${M5Stack_Unit_C6L.lib_deps}
+  densaugeo/base64 @ ~1.4.0
+  end2endzone/NonBlockingRTTTL@^1.3.0
+
 [env:M5Stack_Unit_C6L_companion_radio_usb]
 extends = M5Stack_Unit_C6L
 build_flags = ${M5Stack_Unit_C6L.build_flags}