potion_party_leds/main/leds.h

#ifndef _potion_leds_h
#define _potion_leds_h

#include <stdint.h>
#include <stddef.h>
#include <unistd.h>
#include "rom/ets_sys.h"
#include "shared.h"
#include "driver/gpio.h"

// pack the struct to match exactly 8 * 4 = 32bits
struct __attribute__((__packed__)) led_components_t {
    uint8_t global; // global baseline brightness, highest 3 bits should always be ones
    // RGB component values
    uint8_t red;
    uint8_t green;
    uint8_t blue;
};

// union of components and their representation as a u32
// allows for easier sending of data over serial
union led_t {
    struct led_components_t components;
    uint32_t bits;
};

// point on a gradient
struct gradient_point_t {
    union led_t led;    // value of the led at this point
    size_t offset;      // offset (measured in leds) from the beginning
};

// buffer that will be written out to the led strip over serial
// for leds to work, the 
uint32_t g_serial_out_buffer[62];
// 60-long slice of the out buffer that represents the first few leds
union led_t* g_leds = (uint32_t*)(g_serial_out_buffer + 1);

#define CLOCK 4
#define DATA 5

static
void send_leds() {
    LOGLN("Writing to leds");
    // index of the bit being written
    // the first 5 bits represent the bit of the byte represented by the rest of the int
    int write_bit = 0;
    int write_next = 0;

    gpio_set_level(CLOCK, 0);

    while(write_bit < sizeof(g_serial_out_buffer) * 8) {
        // fetch the bit being adressed
        write_next = 0x1 & (g_serial_out_buffer[write_bit >> 5] >> (write_bit & 0x1F));
        // set clock out to high, triggering a rising edge
        gpio_set_level(CLOCK, 1);
        // write bit to data out
        gpio_set_level(DATA, write_next);

        os_delay_us(10);
        // set clock to low, triggering a falling edge
        gpio_set_level(CLOCK, 0);
        os_delay_us(10);

        write_bit++;
    }
}

static
void leds_init() {
    g_serial_out_buffer[0] = 0;
    g_serial_out_buffer[61] = 0xFFFFFFFF;
    for(int i = 0; i < 60; ++i) {
        g_leds[i].components = (struct led_components_t) {
            .red = 255,
            .green = 10,
            .blue = 255,
            .global = 0xE0 | 0
        };
    }

    gpio_config_t config = {
        .intr_type = GPIO_INTR_DISABLE,
        .mode = GPIO_MODE_OUTPUT,
        .pin_bit_mask = 0x18030,
        .pull_up_en = 0,
        .pull_down_en = 0,
    };
    gpio_config(&config);
}

static inline
uint8_t lerp_uint8(uint8_t a, uint8_t b, float t) {
    int dir = b - a;
    return a + t * dir;
}

static inline
void lerp_led(union led_t* out, const union led_t* from, const union led_t* to, float t) {
    out->components.red = lerp_uint8(from->components.red, to->components.red, t);
    out->components.green = lerp_uint8(from->components.green, to->components.green, t);
    out->components.blue = lerp_uint8(from->components.blue, to->components.blue, t);
    uint8_t glob_from = from->components.global & 0x1F;
    uint8_t glob_to = to->components.global & 0x1F;
    out->components.global = 0xE0 | lerp_uint8(glob_from, glob_to, t);
}

static inline
void lerp_points_between(const struct gradient_point_t from, const struct gradient_point_t to) {
    const int dif = to.offset - from.offset;
    float t = 0.f;
    for(int led = from.offset; led < to.offset; ++led) {
        t = (float)(led - from.offset) / (float)dif;
        lerp_led(g_leds + led, &from.led, &to.led, t);
    }
}

static
void leds_set_gradient(struct gradient_point_t* points, size_t points_len) {
    struct gradient_point_t from = points[0];
    struct gradient_point_t to;
    for(int i = 1; i < points_len; ++i) {
        to = points[i];
        lerp_points_between(from, to);
        from = to;
    }

    send_leds();
}

#endif // !_leds_h