STM32F101xx, STM32F102xx, STM32F103xx, STM32F105xx and ...

USB on-the-go full-speed (OTG_FS)
RM0008
26.4 OTG dual role device (DRD)
Figure 261. OTG A-B device connection
V DD
(3)
5 V to V DD
voltage regulator (1)
V DD
(2)
GPIO+IRQ
STM32F105xx
STM32F107xx
PA9
OSC_IN
OSC_OUT
GPIO
PA11
PA12
PA10
EN
Overcurrent
ST20x2
Current-limited
power distribution
switch (2)
5 V Pwr
VBUS
DM
DP
ID
V SS
USB micro-AB connector
ai17115
1. External voltage regulator only needed when building a V BUS powered device
2. ST20x2 only needed if the application has to to support V BUS powered devices. A basic power switch can
be used if 5 V are available on the application board.
3. V DD range is between 2 V and 3.6 V.
26.4.1 ID line detection
The Host or Peripheral (the default) role is assumed depending on the ID input pin. The ID
line status is determined on plugging in the USB, depending on which side of the USB cable
is connected to the micro-AB receptacle.
● If the B-side of the USB cable is connected with a floating ID wire, the integrated pull-up
resistor detects a high ID level and the default Peripheral role is confirmed. In this
configuration the OTG_FS complies with the standard FSM described by section 6.8.2:
On-The-Go B-Device of the On-The-Go Specification Rev1.3 supplement to the
USB2.0.
● If the A-side of the USB cable is connected with a grounded ID, the OTG_FS issues an
ID line status change interrupt (CIDSCHG bit in OTG_FS_GINTSTS) for host software
initialization, and automatically switches to the Host role. In this configuration the
OTG_FS complies with the standard FSM described by section 6.8.1: On-The-Go A-
Device of the On-The-Go Specification Rev1.3 supplement to the USB2.0.
26.4.2 HNP dual role device
The HNP capable bit in the Global USB configuration register (HNPCAP bit in OTG_FS_
GUSBCFG) enables the OTG_FS Core to dynamically change its role from A-Host to A-
peripheral and vice-versa, or from B-Peripheral to B-Host and vice-versa according to the
host negotiation protocol (HNP). The current device status can be read by the combined
values of the Connector ID Status bit in the Global OTG control and status register (CIDSTS
bit in OTG_FS_GOTGCTL) and the current mode of operation bit in the global interrupt and
status register (CMOD bit in OTG_FS_GINTSTS).
698/995 Doc ID 13902 Rev 9