Usb Peripheral; Srp-Capable Peripheral; Figure 304. Usb Peripheral-Only Connection - ST STM32F101 series Reference Manual

USB on-the-go full-speed (OTG_FS)
28.5

USB peripheral

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 A-Peripheral
–
•
B-device
–
• Peripheral only (see
–
Note: 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
from V
BUS
1. Use a regulator to build a bus-powered device.
28.5.1

SRP-capable peripheral

The SRP capable bit in the Global USB configuration register (SRPCAP bit in
OTG_FS_GUSBCFG) enables the OTG_FS to support the session request protocol (SRP).
In this way, it allows the remote A-device to save power by switching off V
session is suspended.
The SRP peripheral mode program model is described in detail in the
request protocol
827/1128
OTG B-device default state if B-side of USB cable is plugged in
OTG A-device state after the HNP switches the OTG_FS to its peripheral role
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).
Figure 304: USB peripheral-only
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.
.

Figure 304. USB peripheral-only connection

section.
DocID13902 Rev 15
connection)
chip-supply
DD
while the USB
BUS
B-device session
RM0008