STM32F10X的芯片，在做CAN扩展数据帧通信时，滤波为屏蔽模式，0号过滤器，在接收扩展数据帧的时候，能够接收
但是在RxMessage.ExtId,只能显示000000XX，最后8位，前面的24位无论发送什么都为0，求各位大神帮忙，谢谢了!
滤波器设置：
CAN_FilterInitStructure.CAN_FilterNumber=1;
CAN_FilterInitStructure.CAN_FilterMode=CAN_FilterMode_IdMask;
CAN_FilterInitStructure.CAN_FilterScale=CAN_FilterScale_32bit;
CAN_FilterInitStructure.CAN_FilterIdHigh= (((u32)0x040c0100<<3)&0xFFFF0000)>>16;
CAN_FilterInitStructure.CAN_FilterIdLow=(((u32)0x040c0100<<3)|CAN_ID_EXT|CAN_RTR_DATA)&0xFFFF;
CAN_FilterInitStructure.CAN_FilterMaskIdHigh=0xffff;
CAN_FilterInitStructure.CAN_FilterMaskIdLow=0xffff;
CAN_FilterInitStructure.CAN_FilterFIFOAssignment=CAN_FIFO0;
CAN_FilterInitStructure.CAN_FilterActivation=ENABLE;
CAN_FilterInit(&CAN_FilterInitStructure);
CAN_ITConfig(CAN1,CAN_IT_FMP0|CAN_IT_EPV, ENABLE);