diff --git a/firmware/sdkconfig.xiao b/firmware/sdkconfig.xiao
index 49c1af4..9885989 100644
--- a/firmware/sdkconfig.xiao
+++ b/firmware/sdkconfig.xiao
@@ -22,3 +22,11 @@ CONFIG_FRAME_XIAO_ANTENNA_INIT=y
 CONFIG_EPD_PIN_DC=16
 CONFIG_EPD_PIN_RST=17
 CONFIG_EPD_PIN_BUSY=21
+
+# Battery reporting: shares GPIO0/D0/A0 with the back button (a
+# high-impedance divider coexists fine with the button's pull-up and
+# deep-sleep wake -- the firmware time-shares the pin). Requires the
+# 2x200k divider from BAT+ to GND, midpoint to this pin, described in
+# docs/hardware.md. Off by default project-wide since most builds (the
+# DevKitC-1 dev board) have no battery wired at all.
+CONFIG_FRAME_BATTERY_ADC_GPIO=0