ERROR ABOUT I.MX6Q GPIO TEST

[浩卢]

hi：

I've got some questions when I test I.mx6q gpio throgh the GPIO-SYSFS feature.

As a picture you can see below，

No matter I input 1 or 0 into gpio199 value , the result is 0.

Pls hlep me ,tks.

*Notice ： I've add this pin as gpio into pinctrl_hog in imx6qdl-sabresd.dtsi.

[BiyongSUN]

Have you set the SION bit?

Please check the following ticket.

Simple GPIO Example - quandry | NXP Community

[浩卢]

I find the gpio expand by i2c can work fine.

You can see picture as below.

[BiyongSUN · Accepted solution]

I cut from  Simple GPIO Example - quandry  some for you.

[浩卢]

Hi

Biyong

I got it.

Tks for your reply. I'm a newer to linux devicetree.

[BiyongSUN]

Please read the Simple GPIO Example - quandry | NXP Community

In the ticket, some one also have quetion exactly the same like you.

And in the ticket, it gives an answer and also test in the i.MX6UL board.

[BiyongSUN]

Because in the i2c, it set the SION bit. as loopback clock.

When you change the fuction to GPIO. The SION still there.

Please check the SION bit.

[浩卢]

I've set

#define MX6QDL_PAD_GPIO_1__GPIO1_IO01               0x224 0x5f4 0x000 0x5 0x1

in the file imx6q-pinfunc.h

and set

MX6QDL_PAD_GPIO_1__GPIO1_IO01 0x80000000

in the file imx6qdl-sabresd.dtsi.

when I echo "0 or 1" > /sys/class/gpio/gpio1/value ,I can see the voltage changed 0->3V3 by using the multimeter .

But when I read the value (cat /sys/class/gpio/gpio1/value) , the result is always 0.

The gpio test is ok by used linux kernel-3.0.101.

@igorpadykov

[igorpadykov]

please set echo in ../direction means that pad is configured

as input and then set input externally.

https://www.kernel.org/doc/Documentation/gpio/sysfs.txt

~igor

[浩卢]

Tks for your reply.

Since I set the GPIO1 input type (echo in > direction).

When I pull up GPIO1  ,I can read result 1 from (cat /sys/class/gpio/gpio1/value).

When I pull down GPIO1 ,I can read result 0 from (cat /sys/class/gpio/gpio1/value).

So,it works ok when the gpio set input type.

But why it doesn't work when the gpio set output type?

[BiyongSUN]

Again here.

Have you set the SION bit?  "SION"

Please check the following ticket.

Simple GPIO Example - quandry | NXP Community

[igorpadykov]

Hi

echo out ../direction means that pad is configured

as output and one can check its signal with oscilloscope.

Best regards

igor

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