From e8e97c0e6bff4e9dd13a335fde0eb1c44a52f4ae Mon Sep 17 00:00:00 2001
From: Drath <drath@drath.cc>
Date: Mon, 16 Mar 2026 01:08:28 +0100
Subject: [PATCH] pre-calculated brightness table

---
 main/light_driver.c | 44 ++++++++++++++++++++++++++++++--------------
 1 file changed, 30 insertions(+), 14 deletions(-)

diff --git a/main/light_driver.c b/main/light_driver.c
index febc929..4bdf721 100644
--- a/main/light_driver.c
+++ b/main/light_driver.c
@@ -6,19 +6,25 @@
 #include "esp_log.h"
 #include "esp_err.h"
 #include <stdbool.h>
+#include <math.h>
 
 static const char* TAG = "light_driver";
 
-static const uint8_t light_gpio = 15;
-static const uint16_t light_pwm_freq = 20000;
-static const ledc_channel_t light_ledc_channel = LEDC_CHANNEL_0;
-static const ledc_mode_t light_ledc_mode = LEDC_LOW_SPEED_MODE;
+/* tweakable stuff */
+static const uint8_t light_gpio = 2;
+static const uint16_t light_pwm_freq = 65000;
 static const ledc_timer_bit_t light_pwm_resolution = LEDC_TIMER_10_BIT;
-static const uint32_t light_max_brightness = (1 << light_pwm_resolution) - 1;
-static const uint32_t light_max_level = 254; // zigbee light level, goes from 0 to 254
+static const double light_lowest_duty_pct = 0.05; // lowest duty percentage where the LEDs still light up nice
 
+/* no need to tweak this stuff */
+static const ledc_channel_t light_ledc_channel = LEDC_CHANNEL_0;
+static const ledc_mode_t light_ledc_speed_mode = LEDC_LOW_SPEED_MODE;
+static const uint32_t light_brightness_steps = (1 << light_pwm_resolution) - 1;
+
+/* global vars */
 static bool light_init_done = false;
 static uint8_t light_current_level = 0;
+static uint16_t gamma_lut[ZIGBEE_LIGHT_LEVELS + 1];
 
 esp_err_t light_driver_set_level(const uint8_t level, const uint16_t transition_ms) {
     if (!light_init_done) {
@@ -27,12 +33,11 @@ esp_err_t light_driver_set_level(const uint8_t level, const uint16_t transition_
     }
 
     light_current_level = level;
-    double brightness = (double)light_current_level / (double)light_max_level;
-    if (brightness > 1) brightness = 1;
-    if (brightness < 0) brightness = 0;
-    const uint32_t duty = (uint32_t)(light_max_brightness * brightness * brightness); // brightness^2 for fast gamma correction
-    ESP_ERROR_CHECK(ledc_set_fade_with_time(light_ledc_mode, light_ledc_channel, duty, transition_ms));
-    ESP_ERROR_CHECK(ledc_fade_start(light_ledc_mode, light_ledc_channel, LEDC_FADE_NO_WAIT));
+    const uint16_t duty = gamma_lut[light_current_level];
+    ESP_ERROR_CHECK(ledc_fade_stop(light_ledc_speed_mode, light_ledc_channel));
+    ESP_ERROR_CHECK(ledc_set_fade_with_time(light_ledc_speed_mode, light_ledc_channel, duty, transition_ms));
+    ESP_ERROR_CHECK(ledc_fade_start(light_ledc_speed_mode, light_ledc_channel, LEDC_FADE_NO_WAIT));
+    ESP_LOGI(TAG, "led set to %d, max is %d", duty, light_brightness_steps);
     return ESP_OK;
 }
 
@@ -42,7 +47,7 @@ esp_err_t light_driver_set_power(const bool power, const uint16_t transition_ms)
 
 esp_err_t light_driver_init(const bool default_state) {
     const ledc_timer_config_t ledc_timer = {
-        .speed_mode = light_ledc_mode,
+        .speed_mode = light_ledc_speed_mode,
         .duty_resolution = light_pwm_resolution,
         .timer_num = LEDC_TIMER_2,
         .freq_hz = light_pwm_freq,
@@ -57,10 +62,21 @@ esp_err_t light_driver_init(const bool default_state) {
         .duty = 0, // Set duty to 0%
         .hpoint = 0
     };
+
+    for (uint8_t i = 0; i <= ZIGBEE_LIGHT_LEVELS; i++)  {
+        const double brightness_pct = (double)i / (double)ZIGBEE_LIGHT_LEVELS;
+        const double gamma_corrected = pow(brightness_pct, 2.2);
+        const double scaled = (double)light_brightness_steps * gamma_corrected * (1 - light_lowest_duty_pct);
+        gamma_lut[i] = (uint16_t)scaled + (uint16_t)((double)light_brightness_steps * light_lowest_duty_pct) + 1;
+    }
+    gamma_lut[0] = 0; // 0 is always completely off
+    if (gamma_lut[ZIGBEE_LIGHT_LEVELS] > light_brightness_steps) gamma_lut[ZIGBEE_LIGHT_LEVELS] = light_brightness_steps;
+    ESP_LOGI(TAG, "pre-computed brightness lookup table");
+
     ESP_ERROR_CHECK(ledc_timer_config(&ledc_timer));
     ESP_ERROR_CHECK(ledc_channel_config(&ledc_channel));
     ESP_ERROR_CHECK(ledc_fade_func_install(0));
-    ESP_LOGI(TAG, "light driver inited, f=%d Hz", light_pwm_freq);
+    ESP_LOGI(TAG, "ledc driver initialized, f=%d Hz, %d step resolution", light_pwm_freq, light_brightness_steps);
     light_init_done = true;
     light_driver_set_power(default_state, 100);
     return ESP_OK;