Enum AsyncKind 

pub enum AsyncKind {
    Interrupt,
    Dma,
}

The async transmission kind for some communication peripheral like UART, I2C and so on.

For async transmission, it means you could not blocking to wait the transmission action completed. You can switch the processor to do other codes when wait for the remote feedback signal or in the time of register operation.

Variants

Interrupt

Transmit data in interrupt, it not a real asyn transmission. The processor will also take the responsibility of the transmission. But the difference is you cound not be blocked in your code.

Dma

Transmis data with DAM, it is a real async transmission, DMA will do the transmission.