feat(battery): Add BAS GATT reporting

app/CMakeLists.txt

@@ -54,6 +54,7 @@ endif()
 target_sources_ifdef(CONFIG_ZMK_RGB_UNDERGLOW app PRIVATE src/behaviors/behavior_rgb_underglow.c)
 target_sources_ifdef(CONFIG_ZMK_BLE app PRIVATE src/behaviors/behavior_bt.c)
 target_sources_ifdef(CONFIG_ZMK_BLE app PRIVATE src/ble.c)
+target_sources_ifdef(CONFIG_ZMK_BLE app PRIVATE src/battery.c)
 target_sources_ifdef(CONFIG_ZMK_SPLIT_BLE_ROLE_PERIPHERAL app PRIVATE src/split_listener.c)
 target_sources_ifdef(CONFIG_ZMK_SPLIT_BLE_ROLE_PERIPHERAL app PRIVATE src/split/bluetooth/service.c)
 target_sources_ifdef(CONFIG_ZMK_SPLIT_BLE_ROLE_CENTRAL app PRIVATE src/split/bluetooth/central.c)

app/src/battery.c

@@ -0,0 +1,77 @@
+/*
+ * Copyright (c) 2020 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#include <device.h>
+#include <init.h>
+#include <kernel.h>
+#include <drivers/sensor.h>
+#include <bluetooth/services/bas.h>
+
+#include <logging/log.h>
+
+LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);
+
+struct device *battery;
+
+static int zmk_battery_update(struct device *battery) {
+    struct sensor_value state_of_charge;
+
+    int rc = sensor_sample_fetch_chan(battery, SENSOR_CHAN_GAUGE_STATE_OF_CHARGE);
+
+    if (rc != 0) {
+        LOG_DBG("Failed to fetch battery values: %d", rc);
+        return rc;
+    }
+
+    rc = sensor_channel_get(battery, SENSOR_CHAN_GAUGE_STATE_OF_CHARGE, &state_of_charge);
+
+    if (rc != 0) {
+        LOG_DBG("Failed to get battery state of charge: %d", rc);
+        return rc;
+    }
+
+    LOG_DBG("Setting BAS GATT battery level to %d.", state_of_charge.val1);
+
+    return bt_gatt_bas_set_battery_level(state_of_charge.val1);
+}
+
+static void zmk_battery_work(struct k_work *work) {
+    int rc = zmk_battery_update(battery);
+
+    if (rc != 0) {
+        LOG_DBG("Failed to update battery value: %d.", rc);
+    }
+}
+
+K_WORK_DEFINE(battery_work, zmk_battery_work);
+
+static void zmk_battery_timer(struct k_timer *timer) { k_work_submit(&battery_work); }
+
+K_TIMER_DEFINE(battery_timer, zmk_battery_timer, NULL);
+
+static int zmk_battery_init(struct device *_arg) {
+    battery = device_get_binding("BATTERY");
+
+    if (battery) {
+        LOG_DBG("Found battery reporting device.");
+    } else {
+        LOG_DBG("No battery device labelled BATTERY found.");
+        return -ENODEV;
+    }
+
+    int rc = zmk_battery_update(battery);
+
+    if (rc != 0) {
+        LOG_DBG("Failed to update battery value: %d.", rc);
+        return rc;
+    }
+
+    k_timer_start(&battery_timer, K_MINUTES(1), K_MINUTES(1));
+
+    return 0;
+}
+
+SYS_INIT(zmk_battery_init, APPLICATION, CONFIG_APPLICATION_INIT_PRIORITY);