STM32F101xx, STM32F102xx, STM32F103xx, STM32F105xx and ...

RM0008
USB on-the-go full-speed (OTG_FS)
The HNP program model is described in detail in Section 26.15: OTG_FS programming
model.
26.4.3 SRP dual role device
The SRP capable bit in the global USB configuration register (SRPCAP bit in
OTG_FS_GUSBCFG) enables the OTG_FS Core to switch off the generation of V BUS for
the A-Device to save power. Note that the A-Device is always in charge of driving V BUS
regardless of the host or peripheral role of the OTG_FS.
the SRP A/B-Device program model is described in detail in Section 26.15: OTG_FS
programming model.
26.5 USB peripheral
Note:
This section gives the functional description of the OTG_FS in the USB peripheral mode.
The OTG_FS works as an USB peripheral in the following circumstances:
● OTG B-Peripheral
– OTG B-Device default state if B-side of USB cable is plugged in
● OTG A-Peripheral
– OTG A-Device state after the HNP switches the OTG_FS to its peripheral role
●
●
B-Device
– If the ID line is present, functional and connected to the B-side of the USB cable,
and the HNP-capable bit in the Global USB Configuration register (HNPCAP bit in
OTG_FS_GUSBCFG) is cleared (see On-The-Go Rev1.3 par. 6.8.3).
Peripheral only (see Figure 262: USB peripheral-only connection)
– The force device mode bit in the Global USB configuration register (FDMOD in
OTG_FS_GUSBCFG) is set to 1, forcing the OTG_FS core to work as a USB
peripheral-only (see On-The-Go Rev1.3 par. 6.8.3). In this case, the ID line is
ignored even if present on the USB connector.
To build a bus-powered device implementation in case of the B-Device or Peripheral-only
configuration, an external regulator has to be added that generates the V DD chip-supply
from V BUS .
Doc ID 13902 Rev 9 699/995