如果您用的是51等慢速的单片机可能没什么事情，当用ARM等快速的处理器作大量数据传输时可能会出现丢包的现象。在MCU连续的给主机发包的过程中，主机还没有将上一个包的数据从D12读走（就是D12的缓冲区处于满的情况），MCU又将另一个包写进去时会覆盖掉以前的。因此在每写入一个包时必须先判断D12有没有空的缓冲区，-If you use the other 51 may slow the SCM little things, When using such fast ARM processor for massive data transmission may arise dropout phenomenon. MCU in a row to host the contracting process, Host will also not on a packet of data from the D12 Reading walk (D12 is in the buffer zone on the situation), MCU will write another package will get coverage before the swap. Hence each packet into a judgment must first D12 is not empty buffer