feat(xiao_s3_wio): add battery read with voltage divider

variants/xiao_s3_wio/XiaoS3WIOBoard.h

@@ -10,4 +10,24 @@ class XiaoS3WIOBoard : public ESP32Board {
   const char* getManufacturerName() const override {
     return "Xiao S3 WIO";
   }
+  #ifdef PIN_VBAT_READ
+    // battery read support
+    pinMode(PIN_VBAT_READ, INPUT);
+  #endif
+
+  #define BATTERY_SAMPLES 8
+
+  uint16_t getBattMilliVolts() override {
+  #ifdef PIN_VBAT_READ
+    analogReadResolution(ADC_RESOLUTION);
+    uint32_t raw = 0;
+    for (int i = 0; i < 8; i++) {
+      raw += analogRead(PIN_VBAT_READ);
+    }
+    raw = raw / 8;
+    return (uint16_t)((float)raw * REAL_VBAT_MV_PER_LSB);
+  #else
+    return 0;  // not supported
+  #endif
+  }
 };

variants/xiao_s3_wio/platformio.ini

@@ -42,6 +42,7 @@ build_src_filter = ${Xiao_S3_WIO.build_src_filter}
   +<../examples/simple_repeater/*.cpp>
 build_flags =
   ${Xiao_S3_WIO.build_flags}
+  -D PIN_VBAT_READ=D1 ; optionnal voltage divider VBAT
   -D ADVERT_NAME='"XiaoS3 Repeater"'
   -D ADVERT_LAT=0.0
   -D ADVERT_LON=0.0

variants/xiao_s3_wio/variant.h

@@ -0,0 +1,26 @@
+#ifndef _VARIANT_Xiao_S3_WIO_
+#define _VARIANT_Xiao_S3_WIO_
+
+#include "WVariant.h"
+
+// Number of pins defined in PinDescription array
+#define PINS_COUNT (48)
+#define NUM_DIGITAL_PINS (48)
+#define NUM_ANALOG_INPUTS (1)
+#define NUM_ANALOG_OUTPUTS (0)
+
+// Setup for the voltage divider measurement :
+// Label: D1, Analog, GPIO2	
+// 20k resistor wired from battery to D1 
+// and 20k resistor wired from D1 to ground  
+#define ADC_RESOLUTION 14
+
+// built-ins
+#define VBAT_MV_PER_LSB   (0.73242188F)   // 3.0V ADC range and 12-bit ADC resolution = 3000mV/4096
+
+#define VBAT_DIVIDER      (0.5F)          // 200K + 200K voltage divider on VBAT
+#define VBAT_DIVIDER_COMP (2.0F)          // Compensation factor for the VBAT divider
+
+#define REAL_VBAT_MV_PER_LSB (VBAT_DIVIDER_COMP * VBAT_MV_PER_LSB)
+
+#endif