BlueNRG-2: Dma do not working after wakeup

[RJOY.1]

I;m working on bluenrg-2.The system undergo sleep after 3 minutes if no device connected I have to read the ADC value from DMA.Once the system undergo sleep ,the wake up switch will wake up the board.But after wake up the DMA not working. if(DMA_GetFlagStatus(DMA_FLAG_TC2)) failed this condition.Can anyone help me on this issue?

thanks in advance

rose