I have an external board with some buttons that are attached to gpio 20 and 21 which connects these pins to ground when pressed:
simulate this circuit – Schematic created using CircuitLab
I'd like to emit the keys x (fire_left) and o (fire_right) when the buttons are pressed.
I used the following dts file (joystick.dts):
/dts-v1/;
/plugin/;
/ {
compatible = "brcm,bcm2835", "brcm,bcm2708", "brcm,bcm2709", "brcm,bcm2710";
fragment@0 {
target-path = <&gpio>;
__overlay__ {
butt_pins: butt_pins {
brcm,pins = <20 21>; // gpio no.
brcm,function = <0 0>; // 0:in, 1:out
brcm,pull = <2 2>; // 2:up 1:down 0:none
};
};
};
fragment@1 {
target-path = "/";
__overlay__ {
pinctrl-names = "default";
pinctrl-0 = <&butt_pins>;
keypad: joystick {
compatible = "gpio-keys";
#address-cells = <1>;
#size-cells = <0>;
autorepeat;
button@21 {
label = "fire_right";
linux,code = <24>; // o
gpios = <&gpio 21 1>;
};
button@20 {
label = "fire_left";
linux,code = <45>; // x
gpios = <&gpio 20 1>;
};
};
};
};
};
I compiled it with:
dtc -Idts -O dtb -o joystick.dtbo joystick.dts -W no-unit_address_vs_reg
and used the following command to load it:
sudo dtoverlay joystick.dtbo
My problem is, that, although I configured in fragment@0 pullups for the gpios, the Raspberry pi ignored this setting and doesn't set the pullups.
The output of sudo grep gpio /sys/kernel/debug/gpio (buttons are not pressed!):
gpiochip0: GPIOs 0-53, parent: platform/3f200000.gpio, pinctrl-bcm2835:
gpio-20 ( |fire_left ) in lo
gpio-21 ( |fire_right ) in lo
gpiochip2: GPIOs 100-101, brcmvirt-gpio, can sleep:
gpio-100 ( |? ) out hi
gpiochip1: GPIOs 128-135, brcmexp-gpio, can sleep:
gpio-135 ( |? ) in hi
As you can see, gpio-20 and gpio-21 got the correct lable and are set as input. Unfortunately the input value is low and not hight as it would be expected if the pullups where set correctly.
