Implement battery level interface (#24666)

Co-authored-by: Nick Brassel <nick@tzarc.org>

keyboards/handwired/onekey/keymaps/battery/config.h

@@ -0,0 +1,6 @@
+// Copyright 2024 QMK
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#define BATTERY_PIN ADC_PIN

keyboards/handwired/onekey/keymaps/battery/keymap.c

@@ -0,0 +1,28 @@
+// Copyright 2024 QMK
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include QMK_KEYBOARD_H
+#include "battery.h"
+
+const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
+    LAYOUT_ortho_1x1(KC_A)
+};
+
+void keyboard_post_init_user(void) {
+  // Customise these values to desired behaviour
+  debug_enable=true;
+//   debug_matrix=false;
+//   debug_keyboard=true;
+//   debug_mouse=false;
+
+  battery_init();
+}
+
+void housekeeping_task_user(void) {
+    static uint32_t last = 0;
+    if (timer_elapsed32(last) > 2000) {
+        uprintf("Bat: %d!\n", battery_get_percent());
+
+        last = timer_read32();
+    }
+}

keyboards/handwired/onekey/keymaps/battery/keymap.json

@@ -0,0 +1,7 @@
+{
+    "config": {
+        "features": {
+            "console": true
+        }
+    }
+}

keyboards/handwired/onekey/keymaps/battery/rules.mk

@@ -0,0 +1 @@
+BATTERY_DRIVER_REQUIRED = yes