micropython blehid

### MicroPython 实现 BLE HID 的示例代码及实现细节

#### 使用 `pyboard` 或兼容板卡作为基础硬件平台，在 MicroPython 中可以利用内置库来创建 BLE HID 设备。

为了构建一个简单的 BLE HID 键盘设备，以下是具体实现方法：

1. **初始化 BLE 并设置服务**

需要先导入必要的模块并配置基本参数。这包括定义用于报告按键状态的数据结构以及初始化 BLE 接口[^3]。

from ubluetooth import UUID, FLAG_READ | FLAG_WRITE, FLAG_NOTIFY
import bluetooth

hid_service_uuid = UUID(0x1812)  # HID Service UUID
report_char_uuid = UUID(0x2A4D)  # Report Characteristic UUID

# 初始化蓝牙对象
ble = bluetooth.BLE()

2. **注册 HID 服务和特征**

创建 HID 服务并将相应的特性（如输入报告）添加到该服务中。这里使用的是标准的 HID over GATT 协议中的 Input Report 特性[^3]。

def register_services():
    service = (
        hid_service_uuid,
        [
            (report_char_uuid, FLAG_WRITE),
        ],
    )
    
    services = (service,)
    return services

3. **处理连接事件**

当有客户端尝试连接时触发此回调函数。在此处可执行一些额外的操作，比如准备发送初始数据给主机端应用[^3]。

connected_clients = set()

def on_connect(conn_handle):
    global connected_clients
    
    print('New connection')
    connected_clients.add(conn_handle)

def on_disconnect(conn_handle):
    global connected_clients
    
    print('Disconnected')
    try:
        connected_clients.remove(conn_handle)
    except KeyError:
        pass

4. **编写 HID 数据包格式化器**

定义如何打包键盘扫描码成符合 HID 规范的数据帧。对于大多数情况来说，只需关注键按下/释放两种状态即可[^3]。

KEYBOARD_REPORT_ID = const(1)

def make_keyboard_report(keycode=0, modifiers=0):
    report = bytearray([modifiers, 0])  # Modifiers byte followed by reserved zero-byte.
    if keycode != 0:
        report.append(KEYBOARD_REPORT_ID)
        report.extend((keycode,))
        
    while len(report) < 8:  # Ensure the length of keyboard report is always 8 bytes long.
        report.append(0)
        
    return report

5. **发送按键命令至配对设备**

将构造好的 HID 报告通过已建立的 BLE 连接传输给远程设备。注意每次只应传送单个完整的报告单元[^3]。

async def send_keypress(characteristic, key_code):
    characteristic.write(make_keyboard_report(key_code))
    await asyncio.sleep_ms(50)  # Simulate key press duration.
    characteristic.write(make_keyboard_report())  # Release all keys.

6. **启动 BLE HID 应用程序逻辑**

综合上述组件形成完整的工作流程。监听来自用户的输入指令并通过 BLE 发送对应的 HID 命令[^3]。

if __name__ == '__main__':
    ble.active(True)
    ble.config(gap_name="MPY_HID")

    ((input_characteristic,),) = ble.gatts_register_services(register_services())
    
    ble.irq(handler=lambda event, data: {
        1: lambda d: on_connect(d[0]),
        2: lambda d: on_disconnect(d[0])
    }.get(event)(data))

    loop = asyncio.get_event_loop()
    while True:
        if not connected_clients:
            continue
        
        user_input = input("Enter a character to type via BLE:")
        char_to_send = ord(user_input[:1].upper())

        loop.run_until_complete(send_keypress(input_characteristic, char_to_send))

以上就是基于 MicroPython 构建简单 BLE HID 设备的方法概述及其核心部分的源代码片段。实际开发过程中可能还需要考虑更多因素，例如安全性、电源管理等。