STN11xx PowerSave Functionality © 2010 ScanTool.net, LLC www.ScanTool.
STN11xx PowerSave Table of Contents 1.0 PowerSave Functionality ..............................................................................................................................3 1.1 Control Modes .............................................................................................................................................3 1.1.1 Native PowerSave Mode.........................................................................................................................3 1.1.
STN11xx PowerSave 1.0 PowerSave Functionality STN11xx features a sophisticated power management 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). The concept of a trigger is key to understanding the operation of PowerSave.
STN11xx PowerSave randomly toggle the UART communication lines and can unintentionally wake up the device as they are shutting down or entering the standby mode. See section 1.6 for device-specific implementation details. 1.2.4 Voltage Level Sleep 1.2.2 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).
STN11xx PowerSave 1.3.1 UART Rx Pulse Wakeup STN11xx can be configured to wake up on an active pulse detected on the UART Rx input. The host can generate the pulse by holding the Rx line in a logic low state, transmitting an RS232 “break” signal, or sending a character on UART whose bit pattern produces a pulse of the required duration. The wakeup pulse has minimum and maximum timing requirements, which are set using the STSLUWP command, and are accurate to within approximately 5 μs.
STN11xx PowerSave to Digital Converter (ADC for short). The voltage represented by a single bit is called an “ADC step”, and is measured in volts per bit (V/bit). Since the maximum voltage that can be directly measured by the ANALOG_IN pin is very low (about 3V), the pin is normally connected to the voltage source to be measured via an external voltage divider. As its name implies, the voltage divider outputs a voltage that is a fraction of the actual input voltage.
STN11xx PowerSave 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; use one of the voltage-based wakeup triggers instead. 1.6.
STN11xx PowerSave 1.7 Trigger Summary Sleep Triggers Trigger ATLP STSLEEP UART inactivity External SLEEP input Voltage level Trigger UART Rx pulse External SLEEP input Voltage level Voltage change 8 of 13 Default state User initiated. This trigger is available only in ELM327 Low Power mode User initiated, always available Off Off Off Wakeup Triggers Default state On On Off Off www.ScanTool.
STN11xx PowerSave 2.0 PowerSave ST Commands The following sections describe the PowerSave ST commands. For brevity, the “ST” prefix is dropped in the command summary, and throughout the text. However, the STN11xx only accepts the full command, including the ST prefix. For example, the SLCS command must be entered as STSLCS. 2.
STN11xx PowerSave Table 1 – PowerSave Configuration Summary Detail Configuration Summary Line Sec. Description CTRL MODE: 1.1 PowerSave control mode. Reports whether PowerSave module is operating in a native PowerSave control mode, where all settings are configured via the ST commands, or an ELM327 Low Power compatibility mode, where some settings are overridden via the ELM327 programmable parameter 0E. PWR_CTRL: 1.5 PWR_CTRL output pin polarity.
STN11xx PowerSave VL WAKE: voltage threshold in volts ([d]d.ddV) or raw ADC steps (0xhhh)
STN11xx PowerSave SLU sleep, wakeup UART sleep/wakeup triggers on/off. Each of the two parameters can be independently configured as “on” or “off”. The first parameter specifies sleep trigger (UART inactivity timeout) setting, and the second one specifies wakeup trigger (low pulse on UART Rx input) setting. The defaults are sleep = off, wakeup = on. Example: STSLU off, on SLUIT sec Set UART inactivity timeout. The parameter is specified in seconds (decimal). The default is 1200 (20 minutes).
STN11xx PowerSave SLXST ms Specifies how long the SLEEP input must be held in the active (“sleep”) state to put the device to sleep. The ms parameter is the minimum time in milliseconds. The default is 3000 (3 seconds). STN11XXPSB SLXWT ms Specifies how long the SLEEP input must be held in the inactive (“wake”) state to wake the device from sleep. The ms parameter is the minimum time in milliseconds. The default is 2000 (2 seconds). www.ScanTool.