Hi,
For your current software architecture, pls refer to the example in SDK package:
......\LPC_SDK_MCUExpresso\SDK_2_12_0_LPCXpresso54S018 (1)\boards\lpcxpresso54s018\driver_examples\usart\interrupt_transfer
The interrupt transfer example uses interrupt mechanism, for each character, it uses interrupt mode to transfer. In the ISR, the code will check if the predefined size of characters have been transferred, if the predefined size of characters have been completed, the callback function is called, you can write the callback function, set a flag or whatever so that the main can poll the flag to know if the transfer is over or not. But you have to call USART_TransferCreateHandle(DEMO_USART, &g_uartHandle, USART_UserCallback, NULL); so that you can install the callback function.
Hope it can help you
BR
XiangJun Rong
