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/lilygo_techo_lite/TechoBoard.cpp

@@ -0,0 +1,31 @@
+#include <Arduino.h>
+#include <Wire.h>
+
+#include "TechoBoard.h"
+
+#ifdef LILYGO_TECHO
+
+void TechoBoard::begin() {
+  NRF52Board::begin();
+
+  Wire.begin();
+
+  pinMode(SX126X_POWER_EN, OUTPUT);
+  digitalWrite(SX126X_POWER_EN, HIGH);
+  delay(10);   // give sx1262 some time to power up
+}
+
+uint16_t TechoBoard::getBattMilliVolts() {
+  int adcvalue = 0;
+
+  analogReference(AR_INTERNAL_3_0);
+  analogReadResolution(12);
+  delay(10);
+
+  // ADC range is 0..3000mV and resolution is 12-bit (0..4095)
+  adcvalue = analogRead(PIN_VBAT_READ);
+  // Convert the raw value to compensated mv, taking the resistor-
+  // divider into account (providing the actual LIPO voltage)
+  return (uint16_t)((float)adcvalue * REAL_VBAT_MV_PER_LSB);
+}
+#endif