usart_transfer_rb_dma
Overview
The usart dma ring buffer example shows how to use usart driver with DMA driver used:
In this example, a ring buffer was implemented to receive the characters from PC side, to implemente the ring buffer, a descriptor was created and chain itself as the next descriptor, then the DMA transfer will start a continuous transfer.
While data in the ring buffer reach 8 characters, routine will send them out using DMA mode.