Kinetis MicrocontrollersのトピックDisabling External PullUp

Disabling External PullUp

infinity — Fri, 28 Oct 2011 05:48:52 GMT

I'm learning about MQX... but I have a simple problem... how can I change the registry to disable internal pull-up for a GPIO?

I'm using PORTC_PCR10 as digital input.

Thank you.

mjbcswitzerland — Fri, 28 Oct 2011 07:05:05 GMT

Is this not a question for the Kinetis?

The Coldfires have fixed internal pullups (where present) which are enabled by default.

The Kinetis allows configuration of pull-up/down or none.

If you write 0x00000100 to the corresponding PCR register the pin will be configured as GPIO - as input it has no pullup/down.

The pullup/down is only enabled when 0x00000002 is set as well whereby the bit 0x00000001 controls whether this is pullup or pull down.

Regards

Mark

infinity — Fri, 28 Oct 2011 18:11:19 GMT

Oh yes it is true, I put the post in the wrong section.

I'm using TWRK40_512.

How do I move my post? Please some admin can do this for me?

But I still have problems, I set as you said PORTC_PCR10.

But it seems that there is some function call that overwrite this setting and then reactivate the pull-up ... why this behavior?

mjbcswitzerland — Fri, 28 Oct 2011 22:53:01 GMT

This sounds like a software issue so it depends on the SW that you are using.

1) Try puttiung a breakpoint on write accesses to the register to see where it is being written from

2) Or, write the value that you want later (after the unknown function has done its work).

Regards

Mark