Implement battery level interface

builddefs/common_features.mk

@@ -923,6 +923,26 @@ ifeq ($(strip $(DIP_SWITCH_ENABLE)), yes)
     endif
 endif
 
+VALID_BATTERY_DRIVER_TYPES := adc custom
+
+BATTERY_DRIVER ?= adc
+ifeq ($(strip $(BATTERY_DRIVER_REQUIRED)), yes)
+    ifeq ($(filter $(BATTERY_DRIVER),$(VALID_BATTERY_DRIVER_TYPES)),)
+        $(call CATASTROPHIC_ERROR,Invalid BATTERY_DRIVER,BATTERY_DRIVER="$(BATTERY_DRIVER)" is not a valid battery driver)
+    endif
+
+    OPT_DEFS += -DBATTERY_$(strip $(shell echo $(BATTERY_DRIVER) | tr '[:lower:]' '[:upper:]'))
+
+    COMMON_VPATH += $(DRIVER_PATH)/battery
+
+    SRC += battery_$(strip $(BATTERY_DRIVER)).c
+
+    # add extra deps
+    ifeq ($(strip $(BATTERY_DRIVER)), adc)
+        ANALOG_DRIVER_REQUIRED = yes
+    endif
+endif
+
 VALID_WS2812_DRIVER_TYPES := bitbang custom i2c pwm spi vendor
 
 WS2812_DRIVER ?= bitbang

drivers/battery/battery.h

@@ -0,0 +1,10 @@
+// Copyright 2024 QMK
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <stdint.h>
+
+void battery_init(void);
+
+uint8_t battery_get_percent(void);

drivers/battery/battery_adc.c

@@ -0,0 +1,55 @@
+// Copyright 2024 QMK
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "analog.h"
+#include "gpio.h"
+
+#ifndef BATTERY_PIN
+#    error("BATTERY_PIN not configured!")
+#endif
+
+#ifndef BATTERY_REF_VOLTAGE_MV
+#    define BATTERY_REF_VOLTAGE_MV 3300
+#endif
+
+#ifndef BATTERY_VOLTAGE_DIVIDER_R1
+#    define BATTERY_VOLTAGE_DIVIDER_R1 100000
+#endif
+
+#ifndef BATTERY_VOLTAGE_DIVIDER_R2
+#    define BATTERY_VOLTAGE_DIVIDER_R2 100000
+#endif
+
+// TODO: infer from adc config?
+#ifndef BATTERY_ADC_RESOLUTION
+#    define BATTERY_ADC_RESOLUTION 10
+#endif
+
+void battery_init(void) {
+    gpio_set_pin_input(BATTERY_PIN);
+}
+
+uint16_t battery_get_mv(void) {
+    uint32_t raw = analogReadPin(BATTERY_PIN);
+
+    uint32_t bat_mv = raw * BATTERY_REF_VOLTAGE_MV / (1 << BATTERY_ADC_RESOLUTION);
+
+#if BATTERY_VOLTAGE_DIVIDER_R1 > 0 && BATTERY_VOLTAGE_DIVIDER_R2 > 0
+    bat_mv = bat_mv * (BATTERY_VOLTAGE_DIVIDER_R1 + BATTERY_VOLTAGE_DIVIDER_R2) / BATTERY_VOLTAGE_DIVIDER_R2;
+#endif
+
+    return bat_mv;
+}
+
+uint8_t battery_get_percent(void) {
+    uint16_t bat_mv = battery_get_mv();
+
+    // https://github.com/zmkfirmware/zmk/blob/3f7c9d7cc4f46617faad288421025ea2a6b0bd28/app/module/drivers/sensor/battery/battery_common.c#L33
+    if (bat_mv >= 4200) {
+        return 100;
+    } else if (bat_mv <= 3450) {
+        return 0;
+    }
+
+    return bat_mv * 2 / 15 - 459;
+}

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