Initial commit: RNodeTHV4 boundary mode firmware for Heltec V4

Bridges LoRa mesh and TCP/WiFi backbone networks using microReticulum.
Based on microReticulum_Firmware with boundary mode additions:
- BoundaryMode.h: State management and EEPROM persistence
- BoundaryConfig.h: WiFi captive portal for configuration
- TcpInterface.h: TCP backbone interface with HDLC framing
- Display.h: Custom OLED layout with network status indicators
- Transport/Identity library patches for embedded memory constraints

sx127x.h

@@ -0,0 +1,114 @@
+// Copyright Sandeep Mistry, Mark Qvist and Jacob Eva.
+// Licensed under the MIT license.
+
+#ifndef SX1276_H
+#define SX1276_H
+
+#include <Arduino.h>
+#include <SPI.h>
+#include "Modem.h"
+
+#define LORA_DEFAULT_SS_PIN    10
+#define LORA_DEFAULT_RESET_PIN 9
+#define LORA_DEFAULT_DIO0_PIN  2
+#define LORA_DEFAULT_BUSY_PIN  -1
+
+#define PA_OUTPUT_RFO_PIN      0
+#define PA_OUTPUT_PA_BOOST_PIN 1
+
+#define RSSI_OFFSET 157
+
+// Modem status flags
+#define SIG_DETECT 0x01
+#define SIG_SYNCED 0x02
+#define RX_ONGOING 0x04
+
+class sx127x : public Stream {
+public:
+  sx127x();
+
+  int begin(long frequency);
+  void end();
+
+  int beginPacket(int implicitHeader = false);
+  int endPacket();
+
+  int parsePacket(int size = 0);
+  int packetRssi();
+  int packetRssi(uint8_t pkt_snr_raw);
+  int currentRssi();
+  uint8_t packetRssiRaw();
+  uint8_t currentRssiRaw();
+  uint8_t packetSnrRaw();
+  float packetSnr();
+  long packetFrequencyError();
+
+  // from Print
+  virtual size_t write(uint8_t byte);
+  virtual size_t write(const uint8_t *buffer, size_t size);
+
+  // from Stream
+  virtual int available();
+  virtual int read();
+  virtual int peek();
+  virtual void flush();
+
+  void onReceive(void(*callback)(int));
+
+  void receive(int size = 0);
+  void standby();
+  void sleep();
+
+  bool preInit();
+  uint8_t getTxPower();
+  void setTxPower(int level, int outputPin = PA_OUTPUT_PA_BOOST_PIN);
+  uint32_t getFrequency();
+  void setFrequency(unsigned long frequency);
+  void setSpreadingFactor(int sf);
+  long getSignalBandwidth();
+  void setSignalBandwidth(long sbw);
+  void setCodingRate4(int denominator);
+  void setPreambleLength(long preamble_symbols);
+  void setSyncWord(uint8_t sw);
+  bool dcd();
+  void enableCrc();
+  void disableCrc();
+  void enableTCXO();
+  void disableTCXO();
+
+  byte random();
+
+  void setPins(int ss = LORA_DEFAULT_SS_PIN, int reset = LORA_DEFAULT_RESET_PIN, int dio0 = LORA_DEFAULT_DIO0_PIN, int busy = LORA_DEFAULT_BUSY_PIN);
+  void setSPIFrequency(uint32_t frequency);
+
+private:
+  void explicitHeaderMode();
+  void implicitHeaderMode();
+
+  void handleDio0Rise();
+
+  uint8_t readRegister(uint8_t address);
+  void writeRegister(uint8_t address, uint8_t value);
+  uint8_t singleTransfer(uint8_t address, uint8_t value);
+
+  static void onDio0Rise();
+
+  void handleLowDataRate();
+  void optimizeModemSensitivity();
+
+private:
+  SPISettings _spiSettings;
+  int _ss;
+  int _reset;
+  int _dio0;
+  int _busy;
+  long _frequency;
+  int _packetIndex;
+  int _implicitHeaderMode;
+  bool _preinit_done;
+  void (*_onReceive)(int);
+};
+
+extern sx127x sx127x_modem;
+
+#endif