From e8a564b1cf1d1c91c7aba7f6ba39dc16c9d4b9ae Mon Sep 17 00:00:00 2001
From: Arthur Lutz <arthur@lutz.im>
Date: Wed, 17 Jun 2026 12:33:49 +0200
Subject: [PATCH] feat(xiao_s3_wio): add battery read with voltage divider

---
 variants/xiao_s3_wio/XiaoS3WIOBoard.h | 36 +++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/variants/xiao_s3_wio/XiaoS3WIOBoard.h b/variants/xiao_s3_wio/XiaoS3WIOBoard.h
index 7ae06a359b..98283c2c91 100644
--- a/variants/xiao_s3_wio/XiaoS3WIOBoard.h
+++ b/variants/xiao_s3_wio/XiaoS3WIOBoard.h
@@ -3,6 +3,25 @@
 #include <Arduino.h>
 #include <helpers/ESP32Board.h>
 
+/*
+ * This board has no built-in way to read battery voltage.
+ * Nevertheless it's very easy to make it work, you only require two 1% resistors.
+ * If your using the WIO SX1262 Addon for xaio, make sure you dont connect D1!
+ *
+ *    BAT+ -----+
+ *              |
+ *       VSYS --+ -/\/\/\/\- --+
+ *                   200k      |
+ *                             +-- D1
+ *                             |
+ *        GND --+ -/\/\/\/\- --+
+ *              |    100k
+ *    BAT- -----+
+ */
+#define PIN_VBAT_READ     2 // D1
+#define BATTERY_SAMPLES   8
+#define ADC_MULTIPLIER    (3.0f * 3.3f * 1000)
+
 class XiaoS3WIOBoard : public ESP32Board {
 public:
   XiaoS3WIOBoard() { }
@@ -10,4 +29,21 @@ class XiaoS3WIOBoard : public ESP32Board {
   const char* getManufacturerName() const override {
     return "Xiao S3 WIO";
   }
+
+  uint16_t getBattMilliVolts() override {
+#if defined(PIN_VBAT_READ) && defined(ADC_MULTIPLIER)
+    analogReadResolution(12);
+
+    uint32_t raw = 0;
+    for (int i = 0; i < BATTERY_SAMPLES; i++) {
+      raw += analogRead(PIN_VBAT_READ);
+    }
+    raw = raw / BATTERY_SAMPLES;
+
+    return (ADC_MULTIPLIER * raw) / 4096;
+#else
+    return 0;
+#endif
+  }
+
 };