xE922-3GR Hardware User Guide
1VV0301272
Rev.0.8 2017-01-05
Reproduction forbidden without written authorization from Telit Communications S.p.A. - All Rights
Reserved.
Page 57 of 112
9.
USB port
The xE922-3GR module includes a Universal Serial Bus (USB) transceiver, which operates at
USB high-speed (480Mbits/sec). It can also operate with USB full-speed (12Mbits/sec) hosts.
It is compliant with the USB 2.0
‘
DRD
’
dual role specification, 15 endpoints, and can be used
control and data transfers as well as for diagnostic monitoring and firmware update.
The interface does not support ‘OTG’ (HNP) to switch roles on the fly.
Once the module enumerates as a device or host, it stays in that mode. The USB cable needs to
be removed and reconnected to enumerate in the alternate mode.
The USB port on the Telit xE922-3GR is typically the main interface between the module and
OEM hardware.
The USB_D+ and USB_D- signals have a clock rate of 480MHz in HS mode. The signal traces
should be routed carefully. Trace lengths, number of vias and capacitive loading should be
minimized. The impedance value should be as close as possible to 90 Ohms differential.
The table below describes the USB interface signals:
For proper DRD operation USB_ID (W17) should be connected to GPIO1_EINT2 (AT18) to
detect device connection in low power modes.
NOTE:
-
VBUS_DET input power is internally used to detect cable VBUS (USB device attach) and
start enumeration process. It is not used for supplying internal xE922-3GR USB HW block.
NOTE:
In the case of not using USB communication, it is still highly recommended to place an optional
USB connector in the application board.
Signal
xE922-3GR Pad.
Usage
VBUS_DET
AR8
Power sense for the internal USB transceiver.
Minimum high level detect level @ roomtemp: 2.9V
USB_D-
U17
Minus (-) line of the differential, bi-directional USB
signal to/from the peripheral device
USB_D+
S17
Plus (+) line of the differential, bi-directional USB
signal to/from the peripheral device
USB_ID
W17
ID pin to distinguish between host and device side for
dual role DRD USB protocol
GPIO1_EINT2
AT8
Used for SoC USB ID WU from Sleep