ST STM32F413 Reference Manual page 1228

USB on-the-go full-speed (OTG_FS)
could fail to detect the XFRC interrupt (OTG_DOEPINTx) under the following
circumstances:
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2. When the core detects an end of periodic frame before transfer completion to all
isochronous OUT endpoints, it asserts the incomplete Isochronous OUT data interrupt
(INCOMPISOOUT in OTG_GINTSTS), indicating that an XFRC interrupt (in
OTG_DOEPINTx) is not asserted on at least one of the isochronous OUT endpoints. At
this point, the endpoint with the incomplete transfer remains enabled, but no active
transfers remain in progress on this endpoint on the USB.
Application programming sequence:
1. Asserting the INCOMPISOOUT interrupt (OTG_GINTSTS) indicates that in the current
frame, at least one isochronous OUT endpoint has an incomplete transfer.
2. If this occurs because isochronous OUT data is not completely emptied from the
endpoint, the application must ensure that the application empties all isochronous OUT
data (data and status) from the receive FIFO before proceeding.
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3. When it receives an INCOMPISOOUT interrupt (in OTG_GINTSTS), the application
must read the control registers of all isochronous OUT endpoints (OTG_DOEPCTLx) to
determine which endpoints had an incomplete transfer in the current microframe. An
endpoint transfer is incomplete if both the following conditions are met:
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4. The previous step must be performed before the SOF interrupt (in OTG_GINTSTS) is
detected, to ensure that the current frame number is not changed.
5. For isochronous OUT endpoints with incomplete transfers, the application must discard
the data in the memory and disable the endpoint by setting the EPDIS bit in
OTG_DOEPCTLx.
6. Wait for the EPDISD interrupt (in OTG_DOEPINTx) and enable the endpoint to receive
new data in the next frame.
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• Stalling a non-isochronous OUT endpoint
This section describes how the application can stall a non-isochronous endpoint.
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When the receive FIFO cannot accommodate the complete ISO OUT data packet,
the core drops the received ISO OUT data
When the isochronous OUT data packet is received with CRC errors
When the isochronous OUT token received by the core is corrupted
When the application is very slow in reading the data from the receive FIFO
When all data are emptied from the receive FIFO, the application can detect the
XFRC interrupt (OTG_DOEPINTx). In this case, the application must re-enable
the endpoint to receive isochronous OUT data in the next frame.
EONUM bit (in OTG_DOEPCTLx) = FNSOF[0] (in OTG_DSTS)
EPENA = 1 (in OTG_DOEPCTLx)
Because the core can take some time to disable the endpoint, the application may
not be able to receive the data in the next frame after receiving bad isochronous
data.
DocID029473 Rev 3
RM0430