GPIO0_4 with beaglebone black

Dear all,

it looks like I cannot take control of pin gpio0_4 (P9, 18).
I tried to export it by doing
echo 4 > export
in
/sys/class/gpio
but it doesn’t work: I cannot set it as output and move its value and I cannot set it as input to check values.
By doing:
cat /sys/kernel/debug/pinctrl/44e10800.pinmux/pins
I see
pin 86 (44e10958) 00000062 pinctrl-single
which means that it is in I2C1 configuration.
I tried to modify the uEnv.txt to disable I2C1 (even if I think that it should be not implemented by default ) and the I tried to export it again but…nothing.
I also tried to write a dts file and convert it in dtbo (here the text)

/dts-v1/;
/plugin/;

/ {
compatible = “ti,beaglebone”, “ti,beaglebone-black”;

/* identification */
part-number = “GPIO”;
version = “00A0”;

exclusive-use = “P9.18”; /* Digital Input 0 gpio0_4 */

fragment@0 {
target = <&am33xx_pinmux>;
overlay {
end_stop_pins: pinmux_end_stop_pins{
pinctrl-single,pins = <
0x158 0x37 /* P9_18 = Check dig ok */

;
};
};
};

fragment@1 {
target = <&ocp>;
overlay {
#address-cells = <1>;
#size-cells = <1>;
gpio_keys {
compatible = “gpio-keys”;
pinctrl-names = “default”;
pinctrl-0 = <&end_stop_pins>;
#address-cells = <1>;
#size-cells = <0>;
};
};
};
};

but nothing: it is always
pin 86 (44e10958) 00000062 pinctrl-single

and I cannot move it.

Any idea?

Thanks for your help.

Alberto