Srp-Capable Host; Usb Host States; Figure 305. Usb Host-Only Connection - ST STM32F101 series Reference Manual

RM0008
1. STMPS2141STR needed only if the application has to support a V
switch can be used if 5 V are available on the application board.
28.6.1

SRP-capable host

SRP support is available through the SRP capable bit in the global USB configuration
register (SRPCAP bit in OTG_FS_GUSBCFG). With the SRP feature enabled, the host can
save power by switching off the V
The SRP host mode program model is described in detail in the
protocol) section.
28.6.2

USB host states

Host port power
On-chip 5 V V
available on the application board, a basic power switch, must be added externally to drive
the 5 V V
application decides to power on V
power bit in the host port control and status register (PPWR bit in OTG_FS_HPRT).
V valid
BUS
When HNP or SRP is enabled the VBUS sensing pin (PA9) pin should be connected to
V . The V
BUS
during USB operations. Any unforeseen V
(4.25 V) leads to an OTG interrupt triggered by the session end detected bit (SEDET bit in
OTG_FS_GOTGINT). The application is then required to remove the V
the port power bit.
When HNP and SRP are both disabled, the VBUS sensing pin (PA9) should not be
connected to V
The charge pump overcurrent flag can also be used to prevent electrical damage. Connect
the overcurrent flag output from the charge pump to any GPIO input and configure it to
generate a port interrupt on the active level. The overcurrent ISR must promptly disable the
V generation and clear the port power bit.
BUS

Figure 305. USB host-only connection

generation is not supported. For this reason, a charge pump or, if 5 V are
BUS
line. The external charge pump can be driven by any GPIO output. When the
BUS
input ensures that valid V
BUS
. This pin can be can be used as GPIO.
BUS
DocID13902 Rev 15
USB on-the-go full-speed (OTG_FS)
power while the USB session is suspended.
BUS
using the chosen GPIO, it must also set the port
BUS
levels are supplied by the charge pump
BUS
voltage drop below the V
BUS
powered device. A basic power
BUS
A-device session request
valid threshold
BUS
power and clear
BUS
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