gpio

[wgoodrich]

For the i.mx8M:

It is possible to have a 95K pull-down on an output pad, since most pads of the i.mx8 are configured that way coming out of reset.

But in the IOMUXC_SW_PAD_CTL_PAD_xxx registers, the only option is to enable a pull-up (which I assume to be 27K).

Is that really true? Once out of reset, my only option is to enable a pull-up?

[igorpadykov]

Hi Whit

out of reset pad state can not be changed and described in

Table 83. i.MX 8M Dual / 8M QuadLite / 8M Quad 17 x 17 mm functional contact assignments

i.MX8MDQ Datasheet
https://www.nxp.com/docs/en/data-sheet/IMX8MDQLQCEC.pdf

Best regards
igor
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[wgoodrich]

Hi Igor,

Thanks for your reply! I need to re-phrase my question:

When the OS is running and is configuring the Pad control registers, how do

I enable the 90K pull-down when I am setting the other input pad

parameters. If, for example, I set up a GPIO with a Schmitt trigger input

and LVTTL in the pad control register, is the 90K pull-down still there? If

the 90K pull-down is there, how do I disable it? if it’s not there, how do

I enable it (these are the different cases I have across the design).

Thanks!

-Whit Goodrich

Izotope inc.

From: igorpadykov <admin@community.nxp.com>

Sent: Thursday, August 30, 2018 5:31 PM

To: Whit Goodrich <wgoodrich@izotope.com>

Subject: Re: - Re: gpio

NXP Community

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Re: gpio

reply from igorpadykov

<https://community.nxp.com/people/igorpadykov?et=watches.email.thread> in *i.MX

Processors* - View the full discussion

<https://community.nxp.com/message/1052102?commentID=1052102&et=watches.email.thread#comment-1052102>

[igorpadykov]

Hi Whit

processor pad settings (and pull resistor) are set in dts file, as in example

    imx8mq-evk {
        pinctrl_hog: hoggrp {
            fsl,pins = &lt;
                MX8MQ_IOMUXC_NAND_READY_B_GPIO3_IO16        0x19
                MX8MQ_IOMUXC_NAND_WE_B_GPIO3_IO17        0x19

fsl-imx8mq-evk.dts\freescale\dts\boot\arm64\arch - linux-imx - i.MX Linux kernel 

Best regards
igor

[wgoodrich]

Hi Igor,

OK, I think you have answered my question in a round about way:

There is no way in software to control the state of the PULL_DOWN resistor that is present in a GPIO circuit of an IMX8M.  This differs from the operation of the imx6. In the imx8 I can program the state of the GPIO PULL_UP resistor, but not the the PULL_DOWN resistor.

Is that correct?

Thanks,

-Whit