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/xiao_nrf52/XiaoNrf52Board.h

@@ -0,0 +1,57 @@
+#pragma once
+
+#include <MeshCore.h>
+#include <Arduino.h>
+#include <helpers/NRF52Board.h>
+
+#ifndef USER_BTN_PRESSED
+#define USER_BTN_PRESSED LOW
+#endif
+
+#ifdef XIAO_NRF52
+
+class XiaoNrf52Board : public NRF52BoardDCDC {
+protected:
+#if NRF52_POWER_MANAGEMENT
+  void initiateShutdown(uint8_t reason) override;
+#endif
+
+public:
+  XiaoNrf52Board() : NRF52Board("XIAO_NRF52_OTA") {}
+  void begin();
+
+#if defined(P_LORA_TX_LED)
+  void onBeforeTransmit() override {
+    digitalWrite(P_LORA_TX_LED, LOW);   // turn TX LED on
+  }
+  void onAfterTransmit() override {
+    digitalWrite(P_LORA_TX_LED, HIGH);   // turn TX LED off
+  }
+#endif
+
+  uint16_t getBattMilliVolts() override;
+
+  const char* getManufacturerName() const override {
+    return "Seeed Xiao-nrf52";
+  }
+
+  void powerOff() override {
+    // set led on and wait for button release before poweroff
+    digitalWrite(PIN_LED, LOW);
+#ifdef PIN_USER_BTN
+    while(digitalRead(PIN_USER_BTN) == USER_BTN_PRESSED);
+#endif
+    digitalWrite(LED_GREEN, HIGH);
+    digitalWrite(LED_BLUE, HIGH);
+    digitalWrite(PIN_LED, HIGH);
+
+#ifdef PIN_USER_BTN
+    // configure button press to wake up when in powered off state
+    nrf_gpio_cfg_sense_input(digitalPinToInterrupt(g_ADigitalPinMap[PIN_USER_BTN]), NRF_GPIO_PIN_NOPULL, NRF_GPIO_PIN_SENSE_LOW);
+#endif
+
+    sd_power_system_off();
+  }
+};
+
+#endif