USB on-the-go full-speed (OTG_FS) RM0351
1594/1693 DocID024597 Rev 3
43.16 OTG_FS programming model
43.16.1 Core initialization
The application must perform the core initialization sequence. If the cable is connected
during power-up, the current mode of operation bit in the OTG_GINTSTS (CMOD bit in
OTG_GINTSTS) reflects the mode. The OTG_FS controller enters host mode when an “A”
plug is connected or device mode when a “B” plug is connected.
This section explains the initialization of the OTG_FS controller after power-on. The
application must follow the initialization sequence irrespective of host or device mode
operation. All core global registers are initialized according to the core’s configuration:
1. Program the following fields in the OTG_GAHBCFG register:
– Global interrupt mask bit GINTMSK = 1
– Rx FIFO non-empty (RXFLVL bit in OTG_GINTSTS)
– Periodic Tx FIFO empty level
2. Program the following fields in the OTG_GUSBCFG register:
– HNP capable bit
– SRP capable bit
– OTG_FS timeout calibration field
– USB turnaround time field
3. The software must unmask the following bits in the OTG_GINTMSK register:
OTG interrupt mask
Mode mismatch interrupt mask
4. The software can read the CMOD bit in OTG_GINTSTS to determine whether the
OTG_FS controller is operating in host or device mode.
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