NAK没有通讯错误。它只是指出该设备还没有准备好发送回复或者说有没有数据在这一刻发送。据我所知，在此功能的NAK限制将只是确保有该功能的定义的结束。全速USB的情况下，将NAK每1ms产生。有关NAK更多信息，试试这个： http://www.beyondlogic.org/usbnutshell/ usb3.shtml＃USBPacketTypes

NAK is no Communication error. It simply states that the Device is not ready to send a reply or that there are no data to send at this moment. As I understand it the NAK limit in this function will just make sure that there's a defined end for the function. In case of Full Speed USB a NAK will be generated every 1ms. For more information about the NAK try this: http://www.beyondlogic.org/usbnutshell/usb3.shtml#USBPacketTypes