在Android下如何调用UART口

在Android下调用UART口，一般需要以下几个步骤：

1. 打开UART口：通过打开/dev/ttySx或/dev/ttyUSBx设备节点，使用open()函数打开UART口，获取UART口的文件描述符。

2. 配置UART口：通过ioctl()函数，设置UART口的通信参数，如波特率、数据位、停止位、校验位等。

3. 读取和写入数据：通过read()和write()函数，从UART口读取数据或向UART口写入数据。

4. 关闭UART口：使用close()函数关闭UART口的文件描述符。

需要注意的是，Android系统的权限管理机制比较严格，访问UART口需要申请相应的权限。在AndroidManifest.xml文件中，需要添加如下权限声明：

<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE" />
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.WAKE_LOCK" />
<uses-permission android:name="android.permission.READ_PHONE_STATE" />
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_LOCATION_EXTRA_COMMANDS" />
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.RECORD_AUDIO" />
<uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />
<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />
<uses-permission android:name="android.permission.VIBRATE" />
<uses-permission android:name="android.permission.FLASHLIGHT" />
<uses-permission android:name="android.permission.READ_LOGS" />
<uses-permission android:name="android.permission.GET_TASKS" />
<uses-permission android:name="android.permission.RESTART_PACKAGES" />
<uses-permission android:name="android.permission.KILL_BACKGROUND_PROCESSES" />
<uses-permission android:name="android.permission.WRITE_SETTINGS" />
<uses-permission android:name="android.permission.ACCESS_SUPERUSER" />
<uses-permission android:name="android.permission.SYSTEM_OVERLAY_WINDOW" />
<uses-permission android:name="android.permission.SET_DEBUG_APP" />
<uses-permission android:name="android.permission.SET_PROCESS_LIMIT" />
<uses-permission android:name="android.permission.SET_ALWAYS_FINISH" />
<uses-permission android:name="android.permission.SEND_SMS" />
<uses-permission android:name="android.permission.RECEIVE_SMS" />
<uses-permission android:name="android.permission.WRITE_SMS" />
<uses-permission android:name="android.permission.READ_SMS" />
<uses-permission android:name="android.permission.RECEIVE_MMS" />
<uses-permission android:name="android.permission.RECEIVE_WAP_PUSH" />
<uses-permission android:name="android.permission.WRITE_APN_SETTINGS" />
<uses-permission android:name="android.permission.WRITE_SECURE_SETTINGS" />
<uses-permission android:name="android.permission.INSTALL_PACKAGES" />
<uses-permission android:name="android.permission.DELETE_PACKAGES" />
<uses-permission android:name="android.permission.CLEAR_APP_CACHE" />
<uses-permission android:name="android.permission.DELETE_CACHE_FILES" />
<uses-permission android:name="android.permission.MOVE_PACKAGE" />
<uses-permission android:name="android.permission.CHANGE_COMPONENT_ENABLED_STATE" />
<uses-permission android:name="android.permission.READ_CALL_LOG" />
<uses-permission android:name="android.permission.WRITE_CALL_LOG" />
<uses-permission android:name="android.permission.ADD_VOICEMAIL" />
<uses-permission android:name="android.permission.USE_SIP" />
<uses-permission android:name="android.permission.PROCESS_OUTGOING_CALLS" />
<uses-permission android:name="android.permission.WRITE_CONTACTS" />
<uses-permission android:name="android.permission.READ_CONTACTS" />
<uses-permission android:name="android.permission.GET_ACCOUNTS" />
<uses-permission android:name="android.permission.AUTHENTICATE_ACCOUNTS" />
<uses-permission android:name="android.permission.MANAGE_ACCOUNTS" />
<uses-permission android:name="android.permission.READ_PROFILE" />
<uses-permission android:name="android.permission.WRITE_PROFILE" />
<uses-permission android:name="android.permission.READ_SOCIAL_STREAM" />
<uses-permission android:name="android.permission.WRITE_SOCIAL_STREAM" />
<uses-permission android:name="android.permission.READ_USER_DICTIONARY" />
<uses-permission android:name="android.permission.WRITE_USER_DICTIONARY" />
<uses-permission android:name="android.permission.READ_INPUT_STATE" />
<uses-permission android:name="android.permission.BROADCAST_SMS" />
<uses-permission android:name="android.permission.BROADCAST_WAP_PUSH" />
<uses-permission android:name="android.permission.BROADCAST_PACKAGE_REMOVED" />
<uses-permission android:name="android.permission.BROADCAST_PACKAGE_CHANGED" />
<uses-permission android:name="android.permission.BROADCAST_PACKAGE_ADDED" />
<uses-permission android:name="android.permission.SEND_DOWNLOAD_COMPLETED_INTENTS" />
<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
<uses-permission android:name="android.permission.RESTART_PACKAGES" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_PHONE_STATE" />
<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
<uses-permission android:name="android.permission.WAKE_LOCK" />
<uses-permission android:name="android.permission.RECORD_AUDIO" />
<uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.FLASHLIGHT" />
<uses-permission android:name="android.permission.VIBRATE" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.GET_TASKS" />
<uses-permission android:name="android.permission.MANAGE_ACCOUNTS" />
<uses-permission android:name="android.permission.USE_CREDENTIALS" />
<uses-permission android:name="android.permission.READ_SYNC_SETTINGS" />
<uses-permission android:name="android.permission.WRITE_SYNC_SETTINGS" />
<uses-permission android:name="android.permission.AUTHENTICATE_ACCOUNTS" />
<uses-permission android:name="android.permission.READ_CONTACTS" />
<uses-permission android:name="android.permission.WRITE_CONTACTS" />
<uses-permission android:name="android.permission.GET_ACCOUNTS" />
<uses-permission android:name="android.permission.READ_PROFILE" />
<uses-permission android:name="android.permission.WRITE_PROFILE" />
<uses-permission android:name="android.permission.BROADCAST_STICKY" />
<uses-permission android:name="android.permission.BLUETOOTH" />
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
<uses-permission android:name="android.permission.RECORD_VIDEO" />
<uses-permission android:name="android.permission.READ_FRAME_BUFFER" />
<uses-permission android:name="android.permission.PERSISTENT_ACTIVITY" />
<uses-permission android:name="android.permission.SET_DEBUG_APP" />
<uses-permission android:name="android.permission.INSTALL_LOCATION_PROVIDER" />
<uses-permission android:name="android.permission.REORDER_TASKS" />
<uses-permission android:name="android.permission.SET_PREFERRED_APPLICATIONS" />
<uses-permission android:name="android.permission.READ_SYNC_STATS" />
<uses-permission android:name="android.permission.WRITE_SYNC_STATS" />
<uses-permission android:name="android.permission.GLOBAL_SEARCH" />
<uses-permission android:name="android.permission.SET_WALLPAPER" />
<uses-permission android:name="android.permission.SET_WALLPAPER_HINTS" />
<uses-permission android:name="android.permission.ACCESS_ALL_DOWNLOADS" />
<uses-permission android:name="android.permission.DOWNLOAD_WITHOUT_NOTIFICATION" />
<uses-permission android:name="android.permission.SET_TIME_ZONE" />
<uses-permission android:name="android.permission.EXPAND_STATUS_BAR" />
<uses-permission android:name="android.permission.SET_ORIENTATION" />
<uses-permission android:name="android.permission.BATTERY_STATS" />
<uses-permission android:name="android.permission.MOUNT_FORMAT_FILESYSTEMS" />
<uses-permission android:name="android.permission.CLEAR_APP_CACHE" />
<uses-permission android:name="android.permission.SEND_SMS" />
<uses-permission android:name="android.permission.WRITE_SMS" />
<uses-permission android:name="android.permission.RECEIVE_MMS" />
<uses-permission android:name="android.permission.RECEIVE_WAP_PUSH" />
<uses-permission android:name="android.permission.WRITE_APN_SETTINGS" />
<uses-permission android:name="android.permission.READ_LOGS" />
<uses-permission android:name="android.permission.SET_POINTER_SPEED" />
<uses-permission android:name="android.permission.SET_KEYBOARD_LAYOUT" />
<uses-permission android:name="android.permission.INTERNAL_SYSTEM_WINDOW" />
<uses-permission android:name="android.permission.MANAGE_APP_TOKENS" />
<uses-permission android:name="android.permission.CAMERA_DISABLE_TRANSMIT_LED" />
<uses-permission android:name="android.permission.RECEIVE_DATA_ACTIVITY_CHANGE" />
<uses-permission android:name="android.permission.RECEIVE_USER_PRESENT" />
<uses-permission android:name="android.permission.READ_PHONE_STATE_PRIVILEGED" />
<uses-permission android:name="android.permission.UPDATE_DEVICE_STATS" />
<uses-permission android:name="android.permission.ACCESS_CACHE_FILESYSTEM" />
<uses-permission android:name="android.permission.COPY_PROTECTED_DATA" />
<uses-permission android:name="android.permission.ASEC_ACCESS" />
<uses-permission android:name="android.permission.ASEC_CREATE" />
<uses-permission android:name="android.permission.ASEC_DESTROY" />
<uses-permission android:name="android.permission.ASEC_MOUNT_UNMOUNT" />
<uses-permission android:name="android.permission.ASEC_RENAME" />
<uses-permission android:name="android.permission.ASEC_UNSHARE" />
<uses-permission android:name="android.permission.ASEC_SHARE" />
<uses-permission android:name="android.permission.WRITE_GSERVICES" />
<uses-permission android:name="android.permission.READ_GSERVICES" />
<uses-permission android:name="android.permission.DELETE_PACKAGES" />
<uses-permission android:name="android.permission.READ_SYNC_SETTINGS" />
<uses-permission android:name="android.permission.WRITE_SYNC_SETTINGS" />
<uses-permission android:name="android.permission.READ_SYNC_STATS" />
<uses-permission android:name="android.permission.WRITE_SYNC_STATS" />
<uses-permission android:name="android.permission.INTERNAL_SYSTEM_WINDOW" />
<uses-permission android:name="android.permission.MANAGE_APP_TOKENS" />
<uses-permission android:name="android.permission.CAMERA_DISABLE_TRANSMIT_LED" />
<uses-permission android:name="android.permission.RECEIVE_DATA_ACTIVITY_CHANGE" />
<uses-permission android:name="android.permission.RECEIVE_USER_PRESENT" />
<uses-permission android:name="android.permission.READ_PHONE_STATE_PRIVILEGED" />
<uses-permission android:name="android.permission.UPDATE_DEVICE_STATS" />
<uses-permission android:name="android.permission.ACCESS_CACHE_FILESYSTEM" />
<uses-permission android:name="android.permission.COPY_PROTECTED_DATA" />
<uses-permission android:name="android.permission.ASEC_ACCESS" />
<uses-permission android:name="android.permission.ASEC_CREATE" />
<uses-permission android:name="android.permission.ASEC_DESTROY" />
<uses-permission android:name="android.permission.ASEC_MOUNT_UNMOUNT" />
<uses-permission android:name="android.permission.ASEC_RENAME" />
<uses-permission android:name="android.permission.ASEC_UNSHARE" />
<uses-permission android:name="android.permission.ASEC_SHARE" />

同时，还需要在代码中申请权限，例如：

if (ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
    ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1);
}

以上是大致的流程和注意事项，具体实现需要根据具体的需求和使用场景进行调整。