ScanTool STN1100 FRPM - Manual (Page 18)

STN1100
18 of 23 www.obdsol.com STN1100FRPMA
10.0 PowerSave Functionality
STN11xx features a sophisticated power manage-
ment system (PowerSave™) that can be used to put
the device in low power mode. The primary purpose of
PowerSave is to prevent the vehicle’s battery from
being drained when the device is left plugged in for
extended periods of time (e.g., permanent in-vehicle
installations).
Several sleep and wakeup triggers are available.
Each trigger can be independently enabled or disabled.
The following sections describe the PowerSave
functionality, while section 6.3 describes the
commands and parameters used to configure and
control the power management system. You can use
the STSLCS command to print a summary of the the
active PowerSave configuration settings.
10.1 Control Modes
There are two control modes for the PowerSave
functionality: native and ELM327. Use bit 7 (“master
enable”) of the programmable parameter 0E (PP 0E) to
switch between the modes. See the description of the
AT PP command for more information about PP 0E.
By default, STN11xx is in the native PowerSave
control mode.
10.1.1 Native PowerSave Mode
When the “master enable” bit of PP 0E is cleared,
or PP 0E is off, STN11xx is in the native PowerSave
control mode.
In this mode, the rest of the 0E programmable
parameter bits are ignored and the PowerSave is
controlled exclusively via STSL commands. In native
mode, the ATLP command is unavailable. Also, the
ELM327 “ACT ALERT” and “LP ALERT” messages are
not displayed.
10.1.2 ELM327 Low Power Mode
Note: this mode had been implemented for
compatibility with software written for the ELM327. The
native PowerSave mode has a number of important
advantages over the ELM327 Low Power mode,
including higher flexibility, more straightforward
configuration, and default settings that had been
optimized for more reliable performance.
When the “master enable” bit of the 0E
programmable parameter is set and PP 0E is on,
STN11xx is in the ELM327 control mode.
In this mode, most PowerSave settings are
overridden by the PP 0E. However, settings that do not
have their equivalent in the PP 0E can still be adjusted
via their corresponding STSL commands. These
settings are the UART wakeup pulse timing and
external SLEEP control polarity.
By default, instead of the fixed ELM327 minimum
UART Rx wakeup pulse requirement of 128 μs,
STN11xx is set to 0 (20 ns) to allow wakeup via
characters transmitted at the highest supported UART
baud rate.
In the ELM327 PowerSave control mode, STSLCS
command will report the actual active configuration that
is set via the 0E programmable parameter.
STN11xx external SLEEP input functions as the
ELM327 IgnMon input.
10.2 Sleep Triggers
Device can be put to sleep using one of the three
sleep triggers: STSLEEP and ATLP commands,
UART inactivity, and external SLEEP input.
Multiple sleep triggers can be enabled at the same
time. The first trigger that gets activated will put the
device to sleep.
By default, all sleep triggers are off.
Warning: before you enable a sleep trigger or issue
the STSLEEP command, make sure that the wakeup
triggers are enabled and properly configured. The only
other means of bringing the device out of the sleep
state is to do a hardware reset, either via the MCLR
input, or by cycling the power.
10.2.1 STSLEEP and ATLP commands
The device will go to sleep when it receives the
ATLP or STSLEEP command. The ATLP command is
available only in the ELM327 Low Power Mode.
The STSLEEP command has an optional delay
parameter. The purpose of the delay is to prevent the
device from going to sleep prematurely: some hosts
randomly toggle the UART communication lines and
can unintentionally wake up the device as they are
shutting down or entering the standby mode.
10.2.2 UART Inactivity
The STN11xx can be configured to go to sleep
automatically after a period of UART inactivity.
UART inactivity sleep trigger is turned on/off
using the STSLU command (it is off by default). Use
the STSLUIT command to set the UART inactivity
sleep timeout.
Warning: STN11xx UART inactivity sleep trigger is
disabled while any command is executing. Commands
which require UART activity to terminate their
execution, such as the monitoring commands (ATMA,
STMT, etc), or OBD response reception that results in
a continuous stream of messages (for example, if
message filters are set up such that the device is
receiving bus traffic intended for other nodes) may
keep the device awake indefinitely.