topic FlexIO timer output pin pullup/down when timer disabled? in i.MX RT Crossover MCUs

FlexIO timer output pin pullup/down when timer disabled?

jackking — Wed, 15 May 2019 17:57:50 GMT

I am using a FlexIO timer to output to a pin. When the timer is active it behaves as expected.

When I disable the timer, the associated pin seems to have a weak pulldown and starts to wander downwards until the next time I enable the pin and timer output.

How do I define the pullup or down behaviour of the FlexIO pin while the timer is disabled? I would like it to remain high if possible.

Re: FlexIO timer output pin pullup/down when timer disabled?

kerryzhou — Thu, 16 May 2019 12:39:28 GMT

HI Jack King

Please check the IOMUXC configuration for your flexIO pin, that register control the internal pull up or pull low.

Take the SDK as an example, you can find it from the pin_mux.c:

If you still have question about it, please kindly let me know.

Have a great day,
Kerry

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Re: FlexIO timer output pin pullup/down when timer disabled?

jackking — Thu, 16 May 2019 12:48:22 GMT

What I ended up doing was changing the way that the timer is disabled. In the example it uses:

base->flexioBase->TIMCTL[base->timerIndex] = 0U;

This clears out everything including the pin config.

I changed this to only unset the TIMOD bit to disabled and leave the pin config in place:

base->flexioBase->TIMCTL[base->timerIndex] &= 0xFFFFFFFE;

This keeps the FlexIO pin driven high.

Because I was using one of the BOOT_CONFIG MCU pins for the timer output, it has an external 10k pulldown, which I assume was conflicting with the pull-up from the IOMUX config.

Re: FlexIO timer output pin pullup/down when timer disabled?

kerryzhou — Fri, 17 May 2019 06:11:24 GMT

Hi Jack King,

Thanks you for your updated information.

OK, now, if you use:

base->flexioBase->TIMCTL[base->timerIndex] &= 0xFFFFFFFE;

And this keeps the FlexIO pin as high, do you still have any other problem about it?

If it is also the BOOT_CONFIG MCU pins , it really may have conflict. If your pin number is enough to use, you can choose other pin for the FlexIO.

Wish it helps you!

If you still have question about it, please kindly let me know.

Have a great day,
Kerry

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