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/thinknode_m6/ThinkNodeM6Board.h

@@ -0,0 +1,49 @@
+#pragma once
+
+#include <Arduino.h>
+#include <MeshCore.h>
+#include <helpers/NRF52Board.h>
+
+// built-ins
+#define VBAT_MV_PER_LSB   (0.73242188F)   // 3.0V ADC range and 12-bit ADC resolution = 3000mV/4096
+
+#define VBAT_DIVIDER_COMP ADC_MULTIPLIER          // Compensation factor for the VBAT divider
+
+#define PIN_VBAT_READ     BATTERY_PIN
+#define REAL_VBAT_MV_PER_LSB (VBAT_DIVIDER_COMP * VBAT_MV_PER_LSB)
+
+class ThinkNodeM6Board : public NRF52BoardDCDC {
+protected:
+#if NRF52_POWER_MANAGEMENT
+  void initiateShutdown(uint8_t reason) override;
+#endif
+
+public:
+  ThinkNodeM6Board() : NRF52Board("THINKNODE_M6_OTA") {}
+  void begin();
+  uint16_t getBattMilliVolts() override;
+
+#if defined(P_LORA_TX_LED)
+  void onBeforeTransmit() override {
+    digitalWrite(P_LORA_TX_LED, HIGH);   // turn TX LED on
+  }
+  void onAfterTransmit() override {
+    digitalWrite(P_LORA_TX_LED, LOW);   // turn TX LED off
+  }
+#endif
+
+  const char* getManufacturerName() const override {
+    return "Elecrow ThinkNode M6";
+  }
+
+  void powerOff() override {
+
+    // turn off all leds, sd_power_system_off will not do this for us
+    #ifdef P_LORA_TX_LED
+    digitalWrite(P_LORA_TX_LED, LOW);
+    #endif
+
+    // power off board
+    sd_power_system_off();
+  }
+};