iMXRT I/O pad configuration is underdocumented

[udoeb]

Hi,

I'm having difficulties to understand I/O pad configuration details. The reference manual (rev 2) is not clear on that. Documentation is spread across two chapters:  Chapter 10 - IOMUX Controller (IOMUXC), and  Chapter 11 - General Purpose Input/Output (GPIO).

Specific questions:

Q1: IOMUXC_SW_PAD_CTL_* register fields PUE, PKE and PUS. How do these bits correlate? Is the following interpretation correct?

PKE=0  PUE=*  PUS=*   - output is plain, no keeper, no pullup/pulldown

PKE=1  PUE=0  PUS=*  - keeper is active, no pullup/pulldown

PKE=1  PUE=1  PUS=*  - no keeper, pullup/pulldown active according to PUS

Q2: OMUXC_SW_PAD_CTL_* register fields SPEED and SRE. How do these settings correlate? According to Figure 11-3 both settings configure the output driver. The reference manual does not have more details. The data sheet refers to slew rate settings only.

Thanks.

Udo

[fangfang]

Hello,

Q1: IOMUXC_SW_PAD_CTL_* register fields PUE, PKE and PUS. How do these bits correlate? Is the following interpretation correct?

PKE=0  PUE=*  PUS=*   - output is plain, no keeper, no pullup/pulldown

PKE=1  PUE=0  PUS=*  - keeper is active, no pullup/pulldown

PKE=1  PUE=1  PUS=*  - no keeper, pullup/pulldown active according to PUS

#：Theoretically, one can select as it.

Q2: OMUXC_SW_PAD_CTL_* register fields SPEED and SRE. How do these settings correlate? According to Figure 11-3 both settings configure the output driver. The reference manual does not have more details.

#: One can set it as the below:

    

Hope it help you.

Have a great day,
TIC

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[udoeb]

Hi,

Your comment on Q1 is not clear to me. For each of the 3 cases, what I want to know is:

Does the given bit configuration lead to the pin configuration I specified?

PKE=0  PUE=*  PUS=*   - output is plain, no keeper, no pullup/pulldown   correct? YES/NO?

PKE=1  PUE=0  PUS=*  - keeper is active, no pullup/pulldown     correct? YES/ NO?

PKE=1  PUE=1  PUS=*  - no keeper, pullup/pulldown active according to PUS     correct? YES/NO?

Thanks

Udo

[fangfang]

Hello,

PKE=0  PUE=*  PUS=*   - output is plain, no keeper, no pullup/pulldown   correct? YES/NO?

#: Correct, output is Open Drain.

PKE=1  PUE=0  PUS=*  - keeper is active, no pullup/pulldown     correct? YES/ NO?

#: Correct.

PKE=1  PUE=1  PUS=*  - no keeper, pullup/pulldown active according to PUS     correct? YES/NO?

#:Correct