fix(ble): add ble hid change battery level api

Close #385

Author: loop233

examples/bluetooth/ble_remote_control/main/hidd.c

@@ -23,7 +23,7 @@ client_info_t client;
 extern bool is_connected; // Need this here in the case of disconnection
 
 // Characteristic Values
-static const uint8_t val_batt_level = 0;
+static uint8_t val_batt_level = 0;
 // 0% battery level (assume battery not present, for user to modify if need)
 static uint8_t val_bat_cccd[] = {0x01, 0x00};
 // CCCD allows the Central Device to enable/disable notifications/indications
@@ -479,6 +479,7 @@ esp_err_t copy_attribute_handles(int instance_id, uint16_t *handles, int num_han
     switch (instance_id) {
     case INST_ID_BAT_SVC:
         memcpy(handle_table.handles_bat_svc, handles, num_handle * sizeof(uint16_t));
+        client.bat_attr_handle = handles[IDX_BAT_LVL_VAL];
         return ESP_OK;
     case INST_ID_HID:
         memcpy(handle_table.handles_hid_svc, handles, num_handle * sizeof(uint16_t));
@@ -558,3 +559,21 @@ esp_err_t send_user_input(void)
                false   // need_confirm
            );
 }
+
+esp_err_t set_hid_battery_level(uint8_t value)
+{
+    if (value > 100) {
+        value = 100;
+    }
+
+    val_batt_level = value;
+
+    return esp_ble_gatts_send_indicate(
+               client.gatt_if, // gatts_if
+               client.connection_id,   // conn_id
+               client.bat_attr_handle,     // attr_handle
+               1, // value_len
+               &val_batt_level, // value
+               false   // need_confirm
+           );
+}

examples/bluetooth/ble_remote_control/main/hidd.h

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2023 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2023-2024 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -140,6 +140,7 @@ typedef struct {
     esp_gatt_if_t gatt_if;
     uint16_t connection_id;
     uint16_t attr_handle;
+    uint16_t bat_attr_handle;
 } client_info_t;
 
 /**
@@ -164,3 +165,11 @@ void set_hid_report_values(uint8_t joystick_x, uint8_t joystick_y, uint8_t butto
  * @brief Send the HID Report to the client (notification)
 */
 esp_err_t send_user_input(void);
+
+/**
+ * @brief Set the hid battery level value to be sent
+ *
+ * @note Values to be set depends on the device specification
+ * @note The value is capped at 100
+*/
+esp_err_t set_hid_battery_level(uint8_t value);

examples/bluetooth/ble_remote_control/main/main.c

@@ -76,7 +76,7 @@ void joystick_task()
     uint8_t hat_switch = 0; // unused in this example
     uint8_t button_in = 0;
     uint8_t throttle = 0;   // unused in this example
-
+    uint8_t battery_level = 0;
     while (true) {
         DELAY(HID_LATENCY);
 
@@ -121,6 +121,8 @@ void joystick_task()
             set_hid_report_values(x_axis, y_axis, button_in, hat_switch, throttle);
             print_user_input_report(x_axis, y_axis, hat_switch, button_in, throttle);
             ret = send_user_input();
+            battery_level = (battery_level + 1) % 100;
+            set_hid_battery_level(battery_level);
         }
 
         // Alternatively, to simply poll user input can do: