ST STM32L4x6 Reference Manual page 1504

USB on-the-go full-speed (OTG_FS)
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5 OUT endpoints
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Endpoint control
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The following endpoint controls are available to the application through the device
endpoint-x IN/OUT control register (OTG_DIEPCTLx/OTG_DOEPCTLx):
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Endpoint transfer
The device endpoint-x transfer size registers (OTG_DIEPTSIZx/OTG_DOEPTSIZx) allow
the application to program the transfer size parameters and read the transfer status.
Programming must be done before setting the endpoint enable bit in the endpoint control
register. Once the endpoint is enabled, these fields are read-only as the OTG_FS core
updates them with the current transfer status.
The following transfer parameters can be programmed:
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Transfer size in bytes
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Number of packets that constitute the overall transfer size
Endpoint status/interrupt
The device endpoint-x interrupt registers (OTG_DIEPINTx/OTG_DOPEPINTx) indicate the
status of an endpoint with respect to USB- and AHB-related events. The application must
read these registers when the OUT endpoint interrupt bit or the IN endpoint interrupt bit in
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which the transfer is not completed in the current frame. This interrupt is asserted
along with the end of periodic frame interrupt (OTG_GINTSTS/EOPF).
Each of them can be configured to support the isochronous, bulk or interrupt
transfer type
Each of them has a proper control (OTG_DOEPCTLx), transfer configuration
(OTG_DOEPTSIZx) and status-interrupt (OTG_DOEPINTx) register
Device Out endpoints common interrupt mask register (OTG_DOEPMSK) is
available to enable/disable a single kind of endpoint interrupt source on all of the
OUT endpoints (EP0 included)
Support for incomplete isochronous OUT transfer interrupt (INCOMPISOOUT bit
in OTG_GINTSTS), asserted when there is at least one isochronous OUT
endpoint on which the transfer is not completed in the current frame. This interrupt
is asserted along with the end of periodic frame interrupt (OTG_GINTSTS/EOPF).
Endpoint enable/disable
Endpoint activate in current configuration
Program USB transfer type (isochronous, bulk, interrupt)
Program supported packet size
Program Tx FIFO number associated with the IN endpoint
Program the expected or transmitted data0/data1 PID (bulk/interrupt only)
Program the even/odd frame during which the transaction is received or
transmitted (isochronous only)
Optionally program the NAK bit to always negative-acknowledge the host
regardless of the FIFO status
Optionally program the STALL bit to always stall host tokens to that endpoint
Optionally program the SNOOP mode for OUT endpoint not to check the CRC
field of received data
DocID024597 Rev 3
RM0351