ST STM32F40 Series Reference Manual page 1125

USB on-the-go full-speed (OTG_FS)
Disable Channel
if (STALL)
}
else
if (NAK or TXERR)
else
else
The application uses the NPTXFE interrupt in OTG_FS_GINTSTS to find the transmit
FIFO space.
b)
Unmask (NAK/TXERR/XFRC/BBERR/STALL/FRMOR/DTERR)
if (XFRC)
{
Reset Error Count
Mask ACK
if (OTG_FS_HCTSIZx.PKTCNT == 0)
{
De-allocate Channel
}
else
{
Transfer Done = 1
Unmask CHH
Disable Channel
1125/1422
{
Transfer Done = 1
}
{
Rewind Buffer Pointers
Reset Error Count
Mask ACK
Unmask CHH
Disable Channel
}
if (CHH)
{
Mask CHH
if (Transfer Done or (Error_count == 3))
{
De-allocate Channel
}
else
{
Re-initialize Channel (in next b_interval - 1 Frame)
}
}
if (ACK)
{
Reset Error Count
Mask ACK
}
Interrupt IN
Doc ID 018909 Rev 4
RM0090