esp32-led-strip-module

WS2812-compatible RGB LED strip driver for Tactility. It uses ESP-IDF's RMT peripheral to transmit pixel data and provides per-pixel and range color control, brightness adjustment, and gamma-corrected output.

Devicetree Configuration

Declare the strip with the compatible string "espressif,esp32-led-strip". pin-data references the GPIO device and pin used for the data signal; led-count is the number of LEDs on the strip.

ws2812 {
    compatible = "espressif,esp32-led-strip";
    pin-data = <&gpio0 14 GPIO_FLAG_NONE>;
    led-count = <8>;
};

The driver reads these properties into LedStripConfig.

API

Include <tactility/drivers/led_strip.h>. The kernel API operates on a struct Device * and returns error_t; successful calls return ERROR_NONE.

Function	Description
`led_strip_set_single_led_color`	Set one LED using global brightness
`led_strip_set_single_led_color_and_brightness`	Set one LED with an explicit brightness
`led_strip_set_led_range_color`	Set a range from an array of `LedRgb` values using global brightness
`led_strip_set_led_range_color_and_brightness`	Set a range from an array with explicit brightness
`led_strip_fill_led_range_color`	Fill a range using global brightness
`led_strip_fill_led_range_color_and_brightness`	Fill a range with explicit brightness
`led_strip_set_brightness`	Set global brightness
`led_strip_show`	Transmit buffered pixel values to the strip
`led_strip_clear`	Turn off all LEDs
`led_strip_get_length`	Get the configured LED count

LED indices and range offsets are zero-based. Color channels in struct LedRgb range from 0 to 255. Global and per-operation brightness also range from 0 (off) to 255 (full); the default global brightness is 255. Call led_strip_show() after setting colors to transmit the updated buffer. led_strip_clear() clears and refreshes the strip.

Usage Example

#include <tactility/drivers/led_strip.h>

void led_demo(struct Device *strip) {
    uint16_t length = 0;
    if (led_strip_get_length(strip, &length) != ERROR_NONE || length == 0) {
        return;
    }

    led_strip_set_brightness(strip, 128); // About 50% brightness
    led_strip_fill_led_range_color(strip, 0, length, LED_RGB_COLOR_GREEN);
    led_strip_show(strip);

    led_strip_set_single_led_color(strip, 0, LED_RGB_COLOR_RED);
    led_strip_show(strip);

    led_strip_clear(strip);
}

Using Literal RGB Values

Color macros are optional. Initialize struct LedRgb directly when a color is calculated or loaded at runtime. This example assumes the strip has at least four LEDs.

#include <tactility/drivers/led_strip.h>

void show_custom_colors(struct Device *strip) {
    const struct LedRgb colors[] = {
        { .r = 255, .g = 32,  .b = 0   },
        { .r = 0,   .g = 180, .b = 64  },
        { .r = 24,  .g = 48,  .b = 255 },
        { .r = 200, .g = 80,  .b = 160 }
    };

    led_strip_set_led_range_color_and_brightness(strip, 0, 4, colors, 192);
    led_strip_show(strip);
}

Color Presets

The kernel header also provides LED_RGB_COLOR_* macros such as LED_RGB_COLOR_RED, LED_RGB_COLOR_GREEN, and LED_RGB_COLOR_WHITE, plus LED_COLOR_RGB_CUSTOM(r, g, b) for a custom color. These expand to struct LedRgb values.

Implementation Notes

The driver configures the ESP-IDF RMT backend for WS2812 RGB output in GRB component order.
An 8-bit gamma correction lookup table is applied after brightness scaling.
The devicetree compatible string and driver registration are "espressif,esp32-led-strip"; the kernel device type is LED_STRIP_TYPE.

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