Hi,
I would like to set low the logic level on the P9_11 during the power on, so before the linux kernel has bees loaded.
I do not have experince with tree device and boot loader so I am here to ask your help.
For what I was able to discover and collecting fragmentated informations, I have to modify the file “/boot/dtbs/4.14.71-bone-rt-r17/am335x-boneblack-uboot.dtb”.
This file should be responsable for give the earlier informations during the power on start up of the system.
I have decompiled this file and added:
pinmux_P9_11_gpio_pd_pin {
pinctrl-single,pins = <0x70 0x27>;
phandle = <0x180>;
};
P9_11_pinmux {
compatible = “bone-pinmux-helper”;
status = “okay”;
pinctrl-names = “default”, “gpio”, “gpio_pu”, “gpio_pd”, “gpio_input”, “uart”;
pinctrl-0 = <0x17d>;
pinctrl-1 = <0x17e>;
pinctrl-2 = <0x17f>;
pinctrl-3 = <0x180>;
pinctrl-4 = <0x181>;
pinctrl-5 = <0x182>;
};
P9_11 {
gpio-name = “P9_11”;
gpio = <0x35 0x1e 0x0>;
output;
dir-changeable;
};
So, I guess, the system in power up will be able to set up and drive this PIN.
Due to the lack of specific knowledge in this area now I am stuck, I don’t know how to precede.
Please help.