when access a GPIO on iMX28

yongkimin — Wed, 04 Dec 2013 07:13:37 GMT

Hi I ask access a GPIO port on my imx28 platform board.

At first I say thanks to the answer (https://community.freescale.com/message/365311#365311) to Yuri.

According to Yuri's guide I check the /sys/class/gpio as below.

root@freescale /sys/class/gpio$ ls -l

-rwxrwxrwx 1 root root 4096 Jan 1 20:54 export

lrwxrwxrwx 1 root root 0 Jan 1 19:40 gpiochip0 -> ../../devices/virtual/gpio/gpiochip0

lrwxrwxrwx 1 root root 0 Jan 1 19:40 gpiochip128 -> ../../devices/virtual/gpio/gpiochip128

lrwxrwxrwx 1 root root 0 Jan 1 19:40 gpiochip32 -> ../../devices/virtual/gpio/gpiochip32

lrwxrwxrwx 1 root root 0 Jan 1 19:40 gpiochip64 -> ../../devices/virtual/gpio/gpiochip64

lrwxrwxrwx 1 root root 0 Jan 1 19:40 gpiochip96 -> ../../devices/virtual/gpio/gpiochip96

--w------- 1 root root 4096 Jan 1 19:40 unexport

As you can see after configuration (CONFIG_GPIO_SYSFS) and re-build uImage I see the gpio sysfs.

TRe: how to access GPIO on imx28)

But I can't access the GPIO pin after update uImage.

root@freescale /sys/class/gpio$ echo 36 > /sys/class/gpio/export

root@freescale /sys/class/gpio$ ls -l

-rwxrwxrwx 1 root root 4096 Jan 2 00:00 export

lrwxrwxrwx 1 root root 0 Jan 1 19:40 gpiochip0 -> ../../devices/virtual/gpio/gpiochip0

lrwxrwxrwx 1 root root 0 Jan 1 19:40 gpiochip128 -> ../../devices/virtual/gpio/gpiochip128

lrwxrwxrwx 1 root root 0 Jan 1 19:40 gpiochip32 -> ../../devices/virtual/gpio/gpiochip32

lrwxrwxrwx 1 root root 0 Jan 1 19:40 gpiochip64 -> ../../devices/virtual/gpio/gpiochip64

lrwxrwxrwx 1 root root 0 Jan 1 19:40 gpiochip96 -> ../../devices/virtual/gpio/gpiochip96

--w------- 1 root root 4096 Jan 1 19:40 unexport

36 is pin of SSP0_DATA4 and is BANK2_PIN04. After export could not see the gpio.

I did modify mx28evk_fixed_pins the MUX pin of mx28evk_pins.c file in LINUX/arch/arm/march-mx28.

Re: when access a GPIO on iMX28

yongkimin — Wed, 04 Dec 2013 07:19:30 GMT

The modifing is in mx28evk_fixed_pins is

{

.name = "SSP0_DATA4",

.id = PINID_SSP0_DATA4,

.fun = PIN_GPIO,

.strength = PAD_4MA,

.voltage = PAD_3_3V,

.pullup = 1,

.drive = 1,

.pull = 1,

.data = 1,

.output = 1,

I can' understand why I can't access the pin.

Anybody can answer that.

Thanks.

Re: when access a GPIO on iMX28

yongkimin — Fri, 06 Dec 2013 04:50:09 GMT

I did it and refer my other answer (Re: how to access GPIO on imx28).

Other answer is some different in my case. I hope my answer help to you.

Thanks.

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