Otg Dual Role Device (Drd); Figure 303. Otg A-B Device Connection - ST STM32F101 series Reference Manual

USB on-the-go full-speed (OTG_FS)
the physical support to USB connectivity.
The full-speed OTG PHY includes the following components:
•
FS/LS transceiver module used by both host and device. It directly drives transmission
and reception on the single-ended USB lines.
• integrated ID pull-up resistor used to sample the ID line for A/B device identification.
•
DP/DM integrated pull-up and pull-down resistors controlled by the OTG_FS core
depending on the current role of the device. As a peripheral, it enables the DP pull-up
resistor to signal full-speed peripheral connections as soon as V
a valid level (B-session valid). In host mode, pull-down resistors are enabled on both
DP/DM. Pull-up and pull-down resistors are dynamically switched when the device's
role is changed via the host negotiation protocol (HNP).
• Pull-up/pull-down resistor ECN circuit. The DP pull-up consists of 2 resistors controlled
separately from the OTG_FS as per the resistor Engineering Change Notice applied to
USB Rev2.0. The dynamic trimming of the DP pull-up strength allows for better noise
rejection and Tx/Rx signal quality.
• V
BUS
Valid and session-end voltage thresholds. They are used to drive the session request
protocol (SRP), detect valid startup and end-of-session conditions, and constantly
monitor the V
• V
BUS
the SRP (weak drive).
28.4

OTG dual role device (DRD)

1. External voltage regulator only needed when building a V
2. STMPS2141STR needed only if the application has to support a V
switch can be used if 5 V are available on the application board.
825/1128
sensing comparators with hysteresis used to detect V
supply during USB operations.
BUS
pulsing method circuit used to charge/discharge V

Figure 303. OTG A-B device connection

DocID13902 Rev 15
BUS
Valid, A-B Session
BUS
through resistors during
BUS
powered device
BUS
powered device. A basic power
BUS
RM0008
is sensed to be at