User Manual

STN1100
20 of 23 www.obdsol.com STN1100FRPMA
• In sleep mode, current consumption is about
37 mA (54 mA if the USB cable is plugged in
and the virtual COM port is closed).
• External SLEEP control input is not enabled
(ATIGN always returns “ON”, and STSLXS
always returns “WAKE”).
• The “STATUS” LED is not controlled by the
STN1100, and remains on during sleep.
10.5.2 OBDLink Hardware Rev 2.x
OBDLink devices with hardware revision 2.x
implement the SLEEP input as “host present”, which
detects voltage on the USB connector.
When enabled, the SLEEP input trigger can put the
device to sleep when the chip detects that the host is
no longer present. This can happen when the PC shuts
down, enters standby, or when the user unplugs the
USB cable.
Likewise, the SLEEP input can be configured to
wake up the device when the chip detects an active
host.
The STN1100 turns off the “STATUS” LED during
sleep.
Note 1: In sleep mode about 15 mA of current will
be drawn from the USB socket if the host is active. To
maximize power savings, USB must be unplugged or
the host must be shut down or put into standby mode.
Note 2: Wireless add-on modules (Bluetooth, WiFi)
are unpowered in sleep mode. Therefore, it is not
possible to wake up the device over a wireless link.
10.5.3 OBDLink S
In OBDLink S devices, the SLEEP control input is
implemented as “host present”. It is wired to sense
whether a valid RS232 voltage is present on the
RS232 Rx pin (pin 3 of the OBDLink S RS232 DB9
connector).
When enabled, the SLEEP input trigger can put the
device to sleep when the chip detects that the host is
no longer present. This can happen when the PC shuts
down, enters standby, or when the user unplugs the
serial cable.
Likewise, the SLEEP input can be configured to
wake up the device when the chip detects an active
host.
The STN1101 turns off the “STATUS” LED during
sleep.
Note 1: Some non-compliant USB to RS232
converters do not generate valid RS232 voltage levels.
The SLEEP input sleep/wakeup triggers should not be
used with such converters. Use the UART Rx pulse
wakeup trigger (see section 10.3.1) instead. A lower
than norm
al baud rate may be necessary to wake up
reliably, due to the wakeup requirements of the RS232
transceiver IC.
Note 2: In sleep mode, the RS232 transceiver
remains active if there is a valid voltage on the RS232
Rx pin. The transmitter can draw up to several mA of
current, depending on the resistance of the load on the
RS232 Tx line. For maximum power savings, disable
the RS232 transceiver on the host side, shut down the
host, or unplug the serial cable.