clean up xiao nrf52

move variant specific code out of src/helpers
redefine RXEN for alternate radio pinout

variants/xiao_nrf52/XiaoNrf52Board.h

@@ -0,0 +1,66 @@
+#pragma once
+
+#include <MeshCore.h>
+#include <Arduino.h>
+
+#ifdef XIAO_NRF52
+
+// redefine lora pins if using the S3 variant of SX1262 board
+#ifdef SX1262_XIAO_S3_VARIANT
+  #undef P_LORA_DIO_1
+  #undef P_LORA_BUSY
+  #undef P_LORA_RESET
+  #undef P_LORA_NSS
+  #undef SX126X_RXEN
+  #define  P_LORA_DIO_1       D0
+  #define  P_LORA_BUSY        D1
+  #define  P_LORA_RESET       D2
+  #define  P_LORA_NSS         D3
+  #define  SX126X_RXEN        D4
+#endif
+
+class XiaoNrf52Board : public mesh::MainBoard {
+protected:
+  uint8_t startup_reason;
+
+public:
+  void begin();
+  uint8_t getStartupReason() const override { return startup_reason; }
+
+#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 {
+    // Please read befor going further ;)
+    // https://wiki.seeedstudio.com/XIAO_BLE#q3-what-are-the-considerations-when-using-xiao-nrf52840-sense-for-battery-charging
+
+    // We can't drive VBAT_ENABLE to HIGH as long 
+    // as we don't know wether we are charging or not ...
+    // this is a 3mA loss (4/1500)
+    digitalWrite(VBAT_ENABLE, LOW);
+    int adcvalue = 0;
+    analogReadResolution(12);
+    analogReference(AR_INTERNAL_3_0);  
+    delay(10);
+    adcvalue = analogRead(PIN_VBAT);
+    return (adcvalue * ADC_MULTIPLIER * AREF_VOLTAGE) / 4.096;
+  }
+
+  const char* getManufacturerName() const override {
+    return "Seeed Xiao-nrf52";
+  }
+
+  void reboot() override {
+    NVIC_SystemReset();
+  }
+
+  bool startOTAUpdate(const char* id, char reply[]) override;
+};
+
+#endif