GPIO

The kite gpio command gives you direct control over the 11 general-purpose I/O pins on the XIAO BLE connector (D0 through D10). You can configure a pin's direction and pull resistors, then read, write, or toggle it -- all from the shell.

Source: lib/kite/gpio/kite_gpio.c

Commands

Command	Description
kite gpio conf <pin> <flags>	Configure pin direction and electrical properties
kite gpio set <pin> <0\|1>	Drive an output pin high or low
kite gpio get <pin>	Read the logic level of an input pin
kite gpio toggle <pin>	Toggle an output pin

Pin names use the D prefix: D0, D1, ..., D10 (case-insensitive).

Flag Characters

The conf command accepts a compact flag string where each character maps to a Zephyr GPIO flag:

Char	Flag	Meaning
i	GPIO_INPUT	Configure as input
o	GPIO_OUTPUT	Configure as output
u	GPIO_PULL_UP	Enable internal pull-up resistor
d	GPIO_PULL_DOWN	Enable internal pull-down resistor
h	GPIO_ACTIVE_HIGH	Logic level matches electrical level
l	GPIO_ACTIVE_LOW	Logic level is inverted
0	GPIO_OUTPUT_INIT_LOW	Initial output state: low
1	GPIO_OUTPUT_INIT_HIGH	Initial output state: high

Combine them as needed. For example, oh1 means "output, active-high, initially high".

Examples:

uart:~$ kite gpio conf D0 oh1
D0 configured

uart:~$ kite gpio set D0 0
D0 = 0

uart:~$ kite gpio conf D3 iud
D3 configured

uart:~$ kite gpio get D3
D3 = 1

uart:~$ kite gpio toggle D0
D0 toggled

Kconfig

CONFIG_CSSE4011_SHELL_GPIO=y  # default y

This selects GPIO and GPIO_GET_DIRECTION (needed for the set/get/toggle commands to verify the pin is configured in the right direction before operating on it).

Code Walkthrough

Pin Table from Device Tree

The overlay defines 11 GPIO nodes under xiao_gpio_pins with aliases xiao-d0 through xiao-d10. The C code builds a compile-time array from these:

#define XIAO_PIN_SPEC(n) [n] = GPIO_DT_SPEC_GET(DT_ALIAS(xiao_d##n), gpios),

static const struct gpio_dt_spec xiao_pins[] = {
#if DT_NODE_EXISTS(DT_ALIAS(xiao_d0))
    XIAO_PIN_SPEC(0)
#endif
#if DT_NODE_EXISTS(DT_ALIAS(xiao_d1))
    XIAO_PIN_SPEC(1)
#endif
    ...
};

Each #if DT_NODE_EXISTS(...) guard means you can define fewer pins in your overlay without compile errors. The designated initialiser [n] = ... ensures the array index matches the pin number regardless of which pins are present.

The Flag Parser

The parse_flags function converts the user's flag string into a bitmask:

static int parse_flags(const char *str, gpio_flags_t *flags)
{
    *flags = 0;

    for (size_t i = 0; i < strlen(str); i++) {
        switch (str[i]) {
        case 'i': *flags |= GPIO_INPUT;           break;
        case 'o': *flags |= GPIO_OUTPUT;          break;
        case 'u': *flags |= GPIO_PULL_UP;         break;
        case 'd': *flags |= GPIO_PULL_DOWN;       break;
        case 'h': *flags |= GPIO_ACTIVE_HIGH;     break;
        case 'l': *flags |= GPIO_ACTIVE_LOW;      break;
        case '0': *flags |= GPIO_OUTPUT_INIT_LOW;  break;
        case '1': *flags |= GPIO_OUTPUT_INIT_HIGH; break;
        default:  return -EINVAL;
        }
    }
    return 0;
}

The resulting gpio_flags_t bitmask is passed directly to gpio_pin_configure_dt(spec, flags). This replaces the device tree flags entirely for that pin -- the spec still provides the port and pin number, but the user controls the electrical configuration.

Direction Checks

Before writing to a pin, the code verifies it's actually configured as an output:

if (gpio_pin_is_output_dt(spec) != 1) {
    shell_error(sh, "D%d is not configured as output", idx);
    return -EACCES;
}

Similarly, get checks for gpio_pin_is_input_dt. This prevents confusing errors from the GPIO driver and gives the user a clear message about what went wrong. This is why the Kconfig selects GPIO_GET_DIRECTION -- without it, these direction-query functions are not available.

Note

Pins D4 and D5 are shared with the I2C bus (SDA/SCL). If you're using the I2C subsystem, avoid reconfiguring these pins with kite gpio conf.