Initial commit: Simple Sensor firmware for Heltec T114 with BME280

- MeshCore-based Simple Sensor firmware
- Heltec T114 without display
- BME280 sensor support (temp/humidity/pressure)
- Radio: 868.856018 MHz, SF7, BW62.5 kHz, CR4/7
- 2-byte path hash
- PlatformIO project

variants/rak4631/RAK4631Board.cpp

@@ -0,0 +1,53 @@
+#include <Arduino.h>
+#include <Wire.h>
+
+#include "RAK4631Board.h"
+
+#ifdef NRF52_POWER_MANAGEMENT
+// Static configuration for power management
+// Values set in variant.h defines
+const PowerMgtConfig power_config = {
+  .lpcomp_ain_channel = PWRMGT_LPCOMP_AIN,
+  .lpcomp_refsel = PWRMGT_LPCOMP_REFSEL,
+  .voltage_bootlock = PWRMGT_VOLTAGE_BOOTLOCK
+};
+
+void RAK4631Board::initiateShutdown(uint8_t reason) {
+  // Disable LoRa module power before shutdown
+  digitalWrite(SX126X_POWER_EN, LOW);
+
+  if (reason == SHUTDOWN_REASON_LOW_VOLTAGE ||
+      reason == SHUTDOWN_REASON_BOOT_PROTECT) {
+    configureVoltageWake(power_config.lpcomp_ain_channel, power_config.lpcomp_refsel);
+  }
+
+  enterSystemOff(reason);
+}
+#endif // NRF52_POWER_MANAGEMENT
+
+void RAK4631Board::begin() {
+  NRF52BoardDCDC::begin();
+  pinMode(PIN_VBAT_READ, INPUT);
+#ifdef PIN_USER_BTN
+  pinMode(PIN_USER_BTN, INPUT_PULLUP);
+#endif
+
+#ifdef PIN_USER_BTN_ANA
+  pinMode(PIN_USER_BTN_ANA, INPUT_PULLUP);
+#endif
+
+#if defined(PIN_BOARD_SDA) && defined(PIN_BOARD_SCL)
+  Wire.setPins(PIN_BOARD_SDA, PIN_BOARD_SCL);
+#endif
+
+  Wire.begin();
+
+  pinMode(SX126X_POWER_EN, OUTPUT);
+#ifdef NRF52_POWER_MANAGEMENT
+  // Boot voltage protection check (may not return if voltage too low)
+  // We need to call this after we configure SX126X_POWER_EN as output but before we pull high
+  checkBootVoltage(&power_config);
+#endif
+  digitalWrite(SX126X_POWER_EN, HIGH);
+  delay(10);   // give sx1262 some time to power up
+}