如題，uint8_t send_data( unsigned short len, unsigned char *buf )函數(shù)中這樣寫

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s=get_port_status( ); ?/*如果有必要,可以檢查是什么原因導致打印機忙 */

if ( s&0x20 )?

{

??printf("No paper!\n");

??clr_stall( endp_out_addr ); ?/* 清除打印機的數(shù)據(jù)接收端點,或者 soft_reset_print() */

??soft_reset_print(); ?/*打印機出現(xiàn)意外錯誤,軟復位 */

??tog_send = 0; ?/* 操作失敗 */

}

起不到清除緩存的作用，要怎樣處理呢？

打印機類協(xié)議中指明使用SOFT_RESET (bRequest = 2) 。

This class-specific request flushes all buffers and resets the Bulk OUT and Bulk IN pipes to their default states. This
request clears all stall conditions. This reset does NOT change the USB addressing or USB configuration.

還是沒有明白?。?/p>