I have a BBB (running Ubuntu) connected to a custom cape which uses some
GPIO pins for input and output. The output pins work as expected without
any extra configuration, I'm just exporting the required pins in the
/sys/class/gpio folder, setting the direction, and writing values.
One of the GPIOs (specifically GPIO1_15) is connected to a button, which
when pushed I want to shut down the BBB. I export the pin the same way I do
the outputs, set the direction, and try reading the value. The value is
always read as 0, regardless of whether the button is pressed or not. Is
there any extra configuration needed for using GPIO inputs?
Looking at the pinmux for this pin in
/sys/kernel/debug/pinctrl/44e10800.pinmux I get:
pin 15 (44e1083c) 00000027 pinctrl-single
which I take to mean that this pin is already configured for GPIO. I did a
device tree overlay for that pin only for testing purposes, setting it to
0x07. The pinmux changed, but it still behaved the same way. The tree
overlay I tried:
/dts-v1/;
/plugin/;
/ {
compatible = "ti,beaglebone", "ti,beaglebone-black";
/* identification */
part-number = "bb-gpio";
version = "00A0";
exclusive-use =
/* the pin header uses */
"P8.15", /* GPIO1_15 */
/* the hardware ip uses */
"GPIO1_15";
fragment@0 {
target = <&am33xx_pinmux>;
__overlay__ {
bb_GPIO1_15_pins: pinmux_bb_GPIO1_15_pins {
pinctrl-single,pins = <
0x03c 0x07
>;
};
};
};
fragment@1 {
target = <&ocp>;
__overlay__ {
/* avoid stupid warning */
#address-cells = <1>;
#size-cells = <1>;
gpio1_15_test {
compatible = "bone-pinmux-helper";
pinctrl-names = "default";
pinctrl-0 = <&bb_GPIO1_15_pins>;
status = "okay";
};
};
};
};
We tested the cape without a BBB attached and the button sent a signal when
pushed as expected. Any ideas on what is going wrong?
Thanks
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