LISA-U1 series - System Integration Manual
3G.G2-HW-10002-3
Preliminary
System description
Page 57 of 125
LISA-U1 series module identifies itself by its VID (Vendor ID) and PID (Product ID) combination, included in the
USB device descriptor. VID and PID of LISA-U1 series modules are the following:
VID = 0x1546
PID = 0x1101
If the USB interface of LISA-U1 series module is connected to the host before the module switch-on, or if the
module is reset with the USB interface connected to the host, the VID and PID are automatically updated
runtime, after the USB detection. First, VID and PID are the following:
VID = 0x058B
PID = 0x0041
Then, after a time period (~5 s), VID and PID are updated to the following:
VID = 0x1546
PID = 0x1101
1.9.3.2
USB and power saving
If power saving is enabled by AT command (AT+UPSV=1 or AT+UPSV=2), the LISA-U1 series module
automatically enters the USB suspended state when the device has observed no bus traffic for a specified period
(refer to the
Universal Serial Bus Revision 2.0 specification
[7]). In suspended state, the module maintains any
internal status as USB device, including its address and configuration. In addition, the module enters the
suspended state when the hub port it is attached to is disabled: this is referred to as USB selective suspend. The
module exits suspend mode when there is bus activity.
LISA-U1 series module is capable of USB remote wake-up signaling: i.e. may request the host to exit suspend
mode or selective suspend by using electrical signaling to indicate remote wake-up. This notifies the host that it
should resume from its suspended mode, if necessary, and service the external event that triggered the
suspended USB device to signal the host. Remote wake-up is accomplished using electrical signaling described in
the
Universal Serial Bus Revision 2.0 specification
When the USB enters suspended state, the average
VCC
module current consumption of LISA-U1 series module
is ~400 µA higher then when the USB is not attached to a USB host.
If power saving is disabled by AT+UPSV=0 and the LISA-U1 series module is attached to a USB host as USB
device, is configured and is not suspended, the average
VCC
module current consumption in fixed active mode is
increased to ~40 mA.
1.9.3.3
USB application circuit
Since the module acts as a USB device, the USB supply (5.0 V typ.) must be provided to
VUSB_DET
by the
connected USB host. The USB interface is enabled only when a valid voltage as USB supply is detected by the
VUSB_DET
input. Neither the USB interface, nor the whole module is supplied by the
VUSB_DET
input: the
VUSB_DET
senses the USB supply voltage and absorbs few microamperes.
The
USB_D+
and
USB_D-
lines carry the USB serial data and signaling. The lines are used in single ended mode
for relatively low speed signaling handshake, as well as in differential mode for fast signaling and data transfer.
USB pull-up or pull-down resistors on pins
USB_D+
and
USB_D-
as required by the
Universal Serial Bus Revision
[7] are part of the USB pad driver and do not need to be externally provided.
External series resistors on pins
USB_D+
and
USB_D-
as required by the
Universal Serial Bus Revision 2.0
[7] are also integrated: characteristic impedance of
USB_D+
and
USB_D-
lines is specified by the
USB standard. The most important parameter is the differential characteristic impedance applicable for
odd-mode electromagnetic field, which should be as close as possible to 90 differential: signal integrity may
be degraded if the PCB layout is not optimal, especially when the USB signaling lines are very long.
