USB DMA

[yangyongkai]

when I use usb to transfer, i fine many datas are lost.Is it because the DMA size is too small?Where can i see the dma size?(In nrf52833/examples/peripheral/usb_cdc_acm ).Thanks.

[yangyongkai]

Thank you for your reply,There is another question:How do I know that the DMA transfer is over，Is there a transmission end flag and where

[Kenneth]

I assume that is handled in nrfx_usbd_irq_handler():

/** @brief USBD events. */
typedef enum
{
    NRF_USBD_EVENT_USBRESET      = offsetof(NRF_USBD_Type, EVENTS_USBRESET   ), /**< Signals that a USB reset condition is detected on the USB lines. */
    NRF_USBD_EVENT_STARTED       = offsetof(NRF_USBD_Type, EVENTS_STARTED    ), /**< Confirms that the EPIN[n].PTR, EPIN[n].MAXCNT, EPIN[n].CONFIG, or EPOUT[n].PTR, EPOUT[n].MAXCNT, and EPOUT[n].CONFIG registers have been captured on all endpoints reported in the EPSTATUS register. */
    NRF_USBD_EVENT_ENDEPIN0      = offsetof(NRF_USBD_Type, EVENTS_ENDEPIN[0] ), /**< The whole EPIN[0] buffer has been consumed. The RAM buffer can be accessed safely by software. */
    NRF_USBD_EVENT_ENDEPIN1      = offsetof(NRF_USBD_Type, EVENTS_ENDEPIN[1] ), /**< The whole EPIN[1] buffer has been consumed. The RAM buffer can be accessed safely by software. */
    NRF_USBD_EVENT_ENDEPIN2      = offsetof(NRF_USBD_Type, EVENTS_ENDEPIN[2] ), /**< The whole EPIN[2] buffer has been consumed. The RAM buffer can be accessed safely by software. */
    NRF_USBD_EVENT_ENDEPIN3      = offsetof(NRF_USBD_Type, EVENTS_ENDEPIN[3] ), /**< The whole EPIN[3] buffer has been consumed. The RAM buffer can be accessed safely by software. */
    NRF_USBD_EVENT_ENDEPIN4      = offsetof(NRF_USBD_Type, EVENTS_ENDEPIN[4] ), /**< The whole EPIN[4] buffer has been consumed. The RAM buffer can be accessed safely by software. */
    NRF_USBD_EVENT_ENDEPIN5      = offsetof(NRF_USBD_Type, EVENTS_ENDEPIN[5] ), /**< The whole EPIN[5] buffer has been consumed. The RAM buffer can be accessed safely by software. */
    NRF_USBD_EVENT_ENDEPIN6      = offsetof(NRF_USBD_Type, EVENTS_ENDEPIN[6] ), /**< The whole EPIN[6] buffer has been consumed. The RAM buffer can be accessed safely by software. */
    NRF_USBD_EVENT_ENDEPIN7      = offsetof(NRF_USBD_Type, EVENTS_ENDEPIN[7] ), /**< The whole EPIN[7] buffer has been consumed. The RAM buffer can be accessed safely by software. */
    NRF_USBD_EVENT_EP0DATADONE   = offsetof(NRF_USBD_Type, EVENTS_EP0DATADONE), /**< An acknowledged data transfer has taken place on the control endpoint. */
    NRF_USBD_EVENT_ENDISOIN0     = offsetof(NRF_USBD_Type, EVENTS_ENDISOIN   ), /**< The whole ISOIN buffer has been consumed. The RAM buffer can be accessed safely by software. */
    NRF_USBD_EVENT_ENDEPOUT0     = offsetof(NRF_USBD_Type, EVENTS_ENDEPOUT[0]), /**< The whole EPOUT[0] buffer has been consumed. The RAM buffer can be accessed safely by software. */
    NRF_USBD_EVENT_ENDEPOUT1     = offsetof(NRF_USBD_Type, EVENTS_ENDEPOUT[1]), /**< The whole EPOUT[1] buffer has been consumed. The RAM buffer can be accessed safely by software. */
    NRF_USBD_EVENT_ENDEPOUT2     = offsetof(NRF_USBD_Type, EVENTS_ENDEPOUT[2]), /**< The whole EPOUT[2] buffer has been consumed. The RAM buffer can be accessed safely by software. */
    NRF_USBD_EVENT_ENDEPOUT3     = offsetof(NRF_USBD_Type, EVENTS_ENDEPOUT[3]), /**< The whole EPOUT[3] buffer has been consumed. The RAM buffer can be accessed safely by software. */
    NRF_USBD_EVENT_ENDEPOUT4     = offsetof(NRF_USBD_Type, EVENTS_ENDEPOUT[4]), /**< The whole EPOUT[4] buffer has been consumed. The RAM buffer can be accessed safely by software. */
    NRF_USBD_EVENT_ENDEPOUT5     = offsetof(NRF_USBD_Type, EVENTS_ENDEPOUT[5]), /**< The whole EPOUT[5] buffer has been consumed. The RAM buffer can be accessed safely by software. */
    NRF_USBD_EVENT_ENDEPOUT6     = offsetof(NRF_USBD_Type, EVENTS_ENDEPOUT[6]), /**< The whole EPOUT[6] buffer has been consumed. The RAM buffer can be accessed safely by software. */
    NRF_USBD_EVENT_ENDEPOUT7     = offsetof(NRF_USBD_Type, EVENTS_ENDEPOUT[7]), /**< The whole EPOUT[7] buffer has been consumed. The RAM buffer can be accessed safely by software. */
    NRF_USBD_EVENT_ENDISOOUT0    = offsetof(NRF_USBD_Type, EVENTS_ENDISOOUT  ), /**< The whole ISOOUT buffer has been consumed. The RAM buffer can be accessed safely by software. */
    NRF_USBD_EVENT_SOF           = offsetof(NRF_USBD_Type, EVENTS_SOF        ), /**< Signals that a SOF (start of frame) condition has been detected on the USB lines. */
    NRF_USBD_EVENT_USBEVENT      = offsetof(NRF_USBD_Type, EVENTS_USBEVENT   ), /**< An event or an error not covered by the specified events has occurred, check EVENTCAUSE register to find the cause. */
    NRF_USBD_EVENT_EP0SETUP      = offsetof(NRF_USBD_Type, EVENTS_EP0SETUP   ), /**< A valid SETUP token has been received (and acknowledged) on the control endpoint. */
    NRF_USBD_EVENT_DATAEP        = offsetof(NRF_USBD_Type, EVENTS_EPDATA     ), /**< A data transfer has occurred on a data endpoint, indicated by the EPDATASTATUS register. */
}nrf_usbd_event_t;