ST STM32F412 Reference Manual page 1082

USB on-the-go full-speed (OTG_FS)
OTG_HCCHAR1 to control. During the setup stage, the application is expected to set
the PID field in OTG_HCTSIZ1 to SETUP.
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Interrupt OUT transactions
A typical interrupt OUT operation is shown in
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The sequence of operations is as follows:
1. Initialize and enable channel 1. The application must set the ODDFRM bit in
OTG_HCCHAR1.
2. Write the first packet for channel 1.
3. Along with the last word write of each packet, the OTG_FS host writes an entry to the
periodic request queue.
4. The OTG_FS host attempts to send an OUT token in the next (odd) frame.
5. The OTG_FS host generates an XFRC interrupt as soon as the last packet is
transmitted successfully.
6. In response to the XFRC interrupt, reinitialize the channel for the next transfer.
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The application is attempting to send one packet in every frame (up to 1 maximum
packet size), starting with the odd frame (transfer size = 1 024 bytes)
The periodic transmit FIFO can hold one packet (1 KB)
Periodic request queue depth = 4
Figure
RM0402 Rev 6
347. The assumptions are:
RM0402