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Thread: Question re: T4 ONOFF pin

  1. #1
    Senior Member+ Theremingenieur's Avatar
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    Question re: T4 ONOFF pin

    The reference manual tells about timeouts etc. but there is no explanation how I can for example make sure that the T4 does NOT immediately boot when powered up, so that the ONOFF button (wired to GND? Pull-up resistor needed?) has to be pressed to boot the Teensy. A forum search for "ONOFF" gave me the 172 page T4 beta thread as a result, but perhaps someone could point me directly to useful info, please?

  2. #2
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    Paul's T4 breakout blog says
    7.Power On/Off button. Hold for 5 seconds to completely shut off 3.3V power. Press for 1/2 second to turn back on. If a coin cell is installed, the power on/off state will be retained when you disconnect the USB cable. Without the coin cell to maintain power management state, the 3.3V power will default to “on” when power is applied.
    but it seems this was not your question.

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    Senior Member+ Theremingenieur's Avatar
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    Hi WMXZ, that's already a good information, thank you. For a specific application I'd prefer having the default power state = off when external power is applied, even with no coin cell connected. Perhaps, there is a register setting which can be modified. Hoping that @Paul will jump in and shed some light on this...

  4. #4
    Senior Member+ defragster's Avatar
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    Thierry: In my reading of the beta thread I don't recall seeing a way to power up the T4 to OFF. Except as noted if it has VBat and was OFF when unpowered it will then power up to OFF until the 1/2 sec to turn on.

    *Note: if it has VBat power and is OFF and UNPOWERED - pressing the POWER button 1/2 sec will have the T4 ON when powered. That POWER button is part of the VBat powered circuit. So the converse ON to OFF also applies with VBat.

    Testing the PJRC breakout, holding POWER to GND on power up the Teensy still wakes - and powers off in 5 seconds with no VBat. I asked and am not sure what determines the 5 second period.

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    Senior Member+ defragster's Avatar
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    Just saw this post - the reset command puts the T4 in the OFF state it seems from this post :: T4-software-restart-procedure-and-freeram-function

    So in startup you could selectively initiate OFF … perhaps wire one button to GND POWER and also another PIN. In setup() { or early_hook } if that PIN is HIGH do a software power off, if the button is held to WAKE it will be LOW/GND at reset() and don't shutdown?

  6. #6
    Senior Member+ KurtE's Avatar
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    Again not sure if it helps or not...

    But if you look at section 12.5 of the IMXRT1060RM.pdf - There is a section that talks about the ONOFF (button).
    It also shows in in section 19.3 (SNVS Structure)
    External Signal (SRC_ONOFF) 20.3
    Shows again picture of chip Reset on Figure 20-2.
    ...

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