Linux/AM5728: GPIO status change

philos

Part Number: AM5728

Tool/software: Linux

Hello , every time when I use

echo 57 > /sys/class/gpio/export

echo out > /sys/class/gpio/gpio57/direction

then the Gpio 's status(the yellow signal) changed .

Is that normal?

In my project ,this is not expected ,please help me.

over 6 years ago

0 Pavel Botev over 6 years ago

TI__Guru**** 170625 points

Hi Philos,

Do you use AM57x PSDK Linux? If yes, which version?

Do you use AM572x TI board (EVM or IDK) or custom board?

What value you have in below entry?

/sys/class/gpio/gpio57/value

"value" - reads as either 0 (low) or 1 (high). If the GPIO is configured as an output, this value may be written; any nonzero value is treated as high.

Regards,
Pavel

0 philos over 6 years ago in reply to Pavel Botev

Intellectual 520 points

Thanks for reply,Pavel

I am not using PSDK Linux,

because I am using EVM borad(which is also called bb_x15)

cat /sys/class/gpio/gpio57/value

the value is 0.

I searched and found something in

I think maybe I should use

echo 57 > /sys/class/gpio/export
echo high > /sys/class/gpio/gpio57/direction

in order to make sure the status of gpio57 won't change.

0 Pavel Botev over 6 years ago in reply to philos

TI__Guru**** 170625 points

Philos,

In this forum, only PSDK Linux is supported.

From what I understand, gpio57 (yellow signal) is low (0) before you set the direction to output, and you need to stay low after that.

For general direction, I can provide you below hints:

- check if you have internal or external pull up resistor, that is making this signal high. Internal pull up is configured in CTRL_CORE_PAD_x [16] [17] bits

- check what value you have in your GPIO_DATAOUT register, make sure you have 0 for gpio57. Check also GPIO_SETDATAOUT, GPIO_CLEARDATAOUT, and TRM section "27.4.8 General-Purpose Interface Data Input/Output Capabilities"

Regards,
Pavel

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Linux/AM5728: GPIO status change