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OBDLink update: voltage based sleep and wakeup triggers

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  • OBDLink update: voltage based sleep and wakeup triggers

    We just released a firmware update (v2.2.1 RC1) which adds new voltage-based sleep and wakeup triggers:
    • Voltage level sleep
    • Voltage level wakeup
    • Voltage change wakeup

    The new triggers can be configured to put the device to sleep when the engine is shut off, and wake up on engine startup. This release does not show up in the public feed. You can download it from the following link:

    http://www.scantool.net/scantool/dow...link-2.2.1.zip

    The new triggers are described in the updated PowerSave specification:

    http://www.scantool.net/scantool/dow...-powersave.pdf

    Comments and questions are welcome.

    Sincerely,

    Vitaliy
    OBDLink MX: world's smallest, fastest, most advanced OBD/Bluetooth adapter with SW and MS CAN support. Read the review to learn more.
    Need to look up a diagnostic trouble code? Try the most up-to-date, free DTCsearch.com!

    You cannot send me a private message using this forum. Use my email instead: vitaliy[@]scantool.net.

  • #2
    Since the VBAT voltage is always present at the OBDII connector it appears that a separate connection to a switched power source is necessary for the 'voltage sleep' function.
    Would that be correct?

    Comment


    • #3
      Originally posted by Rooster View Post
      Since the VBAT voltage is always present at the OBDII connector it appears that a separate connection to a switched power source is necessary for the 'voltage sleep' function.
      Would that be correct?
      No.

      PowerSave does not simply detect the presence of voltage, it measures its magnitude with accuracy down to one one hundredth of a volt. It then uses that measurement to answer one of the following questions (depending on which triggers are enabled):

      - Is the voltage higher than X?
      - Is the voltage lower than X?
      - Is the voltage difference between two consecutive samples Y seconds apart, larger than X?

      This works because the vehicle system voltage is not constant: for example, it is normally higher when the engine is running and the alternator is charging the battery.

      We plan to publish a paper which describes how the triggers can be used for reliable detection of "engine running" conditions, in different scenarios (including hybrid and electric vehicles).

      Hope this helps,

      Vitaliy
      OBDLink MX: world's smallest, fastest, most advanced OBD/Bluetooth adapter with SW and MS CAN support. Read the review to learn more.
      Need to look up a diagnostic trouble code? Try the most up-to-date, free DTCsearch.com!

      You cannot send me a private message using this forum. Use my email instead: vitaliy[@]scantool.net.

      Comment


      • #4
        OK, I'll buy that.

        I suspect each vehicle will have a unique trigger value, which may change over time.
        What kind of values have you seen in testing?

        Comment


        • #5
          I would think this is not particularly vehicle dependant. Assume at engine off to find vbatt anywhere between 11.5v to 13v. If Voltage exceeds say 13.5v (alternator charges at about 14v) then the engine is running.

          Comment


          • #6
            MX5_Carputer is right, on most "normal" cars with lead-acid batteries the voltage levels are fairly consistent. Our default triggers -- 13.00V for sleep and 13.2V for wake -- should work reliably on most vehicles, provided that the ADC is properly calibrated. OBDLinks are calibrated at the factory, but if you build your own circuit using the STN1110, you have to calibrate it yourself.

            HOWEVER, the voltage difference trigger is the preferred method for wakeup, because it does not depend on the absolute levels, but rather on the relative difference between the samples. It is also what ScanGaugeII uses for its wake up trigger.

            Vitaliy
            OBDLink MX: world's smallest, fastest, most advanced OBD/Bluetooth adapter with SW and MS CAN support. Read the review to learn more.
            Need to look up a diagnostic trouble code? Try the most up-to-date, free DTCsearch.com!

            You cannot send me a private message using this forum. Use my email instead: vitaliy[@]scantool.net.

            Comment


            • #7
              STN11xx PowerSave Sleep/Wakeup Trigger Diagram

              Attached is a diagram showing the different sleep/wakeup triggers. It will eventually be incorporated into the STN11xx documentation, but I wanted to post it here now, to help those of you who are trying to take advantage of the PowerSave functionality.
              Attached Files
              OBDLink MX: world's smallest, fastest, most advanced OBD/Bluetooth adapter with SW and MS CAN support. Read the review to learn more.
              Need to look up a diagnostic trouble code? Try the most up-to-date, free DTCsearch.com!

              You cannot send me a private message using this forum. Use my email instead: vitaliy[@]scantool.net.

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