..\OBJ\NRF24L01.axf: Error: L6218E: Undefined symbol DMA_ClearITPendingBit (referred from i2s.o)...\OBJ\NRF24L01.axf: Error: L6218E: Undefined symbol DMA_FlowControllerConfig (referred from sdio_sdcard.o).
..\OBJ\NRF24L01.axf: Error: L6218E: Undefined symbol TIM_ClearFlag (referred from usmart.o).出现了27个类似的错误,怎么改