If you need a pin set one way or another on boot buffer it
use a tristate gate pull it high or low then after your overlay is loaded
enable the buffer so you have control
On 3/3/2020 10:34 AM, Faby wrote:
Today I tried with an overlay and it works, but with about 12 seconds
of delay.
That is not the expected result, but finally somethings moves.
Any suggestion or advise would be great.
Il giorno giovedì 27 febbraio 2020 16:14:17 UTC+1, Fabrizio Borrello
ha scritto:
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.
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