diff --git a/firmware/user/ch32v20x_it.c b/firmware/user/ch32v20x_it.c
index c54b50b..572066c 100644
--- a/firmware/user/ch32v20x_it.c
+++ b/firmware/user/ch32v20x_it.c
@@ -56,28 +56,24 @@ volatile uint32_t uptime;
 
 void SysTick_Handler(void)
 {
-    if (++ticnt > 0x1ff) {
+    if (++ticnt > 0x3ff) {
         ticnt = 0;
         uptime++;
     }
 
-    // all processes update at 1/128 duty
-    switch (ticnt & 0x3) {
+    // light sensor updates at ~1ms
+    adc_process_lsens();
+
+    // general processes update at 1/128 duty
+    switch (ticnt & 0x7) {
         case 0: {   // send new LEDs
             led_rgb_update();
             led_matrix_send();
             break;
         }
-        case 1: {   // process / initialize light sensor
-            adc_process_lsens(0);
-            break;
-        }
-        case 2: {   // convert light sensor
-            adc_process_lsens(1);
-            break;
-        }
-        case 3: {   // process buttons
+        case 1: {   // process buttons
             btn_poll();
+            break;
         }
     }
 
diff --git a/firmware/user/main.c b/firmware/user/main.c
index 1d055eb..443ac59 100644
--- a/firmware/user/main.c
+++ b/firmware/user/main.c
@@ -36,7 +36,7 @@
 
 void systick_init(void)
 {
-    SysTick->CMP = (SystemCoreClock / 512) - 1;     // we want a 512Hz interrupt
+    SysTick->CMP = (SystemCoreClock / 1024) - 1;    // we want a 1024Hz interrupt
     SysTick->CNT = 0;                               // clear counter
     SysTick->CTLR = 0xF;                            // start counter in /1 mode, enable interrupts, auto-reset counter
     SysTick->SR = 0;                                // clear count comparison flag
@@ -123,6 +123,9 @@ int main(void)
     lis2dw_init();      // looking at badge: Y+ up, X+ right, Z+ in front of badge
     led_init();         // configure matrix IC as well as RGB PWM
 
+    // by default, top LED is in light sense mode
+    adc_set_mode_lsens(LSENS_READING_IDLE);
+
     // configure random
     tinymt32_init(&tinymt32_s, DBGMCU_GetCHIPID() | userconf.checksum);
 
diff --git a/firmware/user/src/adc.c b/firmware/user/src/adc.c
index 9de895d..a287a7f 100644
--- a/firmware/user/src/adc.c
+++ b/firmware/user/src/adc.c
@@ -18,8 +18,12 @@ static GPIO_InitTypeDef lsens_gpio = {
 };
 
 uint16_t lsens_val;
+
 static uint8_t lsens_mode = LSENS_READING_IDLE;
 
+uint8_t lsens_wait;
+uint8_t lsens_coarse = 1;
+
 
 
 void adc_init()
@@ -48,19 +52,16 @@ void adc_convert()
 
 void adc_read()
 {
-    while(!ADC_GetFlagStatus(ADC1, ADC_FLAG_EOC));
-    lsens_val = ADC_GetConversionValue(ADC1);
+    uint16_t timeout = 0xfff;
+    while((!ADC_GetFlagStatus(ADC1, ADC_FLAG_EOC)) && timeout) timeout--;
+    if (timeout) {
+        lsens_val = ADC_GetConversionValue(ADC1);
+    }
 }
 
 void adc_set_mode_lsens(uint8_t mode)
 {
     lsens_mode = mode;
-
-    // always reconfigure the pins as outputs when calling this
-    lsens_gpio.GPIO_Pin = LSENS_A_PIN | LSENS_K_PIN;
-    lsens_gpio.GPIO_Mode = GPIO_Mode_Out_PP;
-    GPIO_Init(LSENS_PORT, &lsens_gpio);
-
 }
 
 uint8_t adc_get_mode_lsens()
@@ -89,15 +90,70 @@ static void lsens_start()
     GPIO_Init(LSENS_PORT, &lsens_gpio);
 }
 
-static void lsens_end()
+static void lsens_stop()
 {
-    adc_set_mode_lsens(LSENS_READING_IDLE);
+    lsens_gpio.GPIO_Pin = LSENS_A_PIN | LSENS_K_PIN;
+    lsens_gpio.GPIO_Mode = GPIO_Mode_Out_PP;
+    GPIO_Init(LSENS_PORT, &lsens_gpio);
+
+    lsens_mode = LSENS_READING_IDLE;
 }
 
-void adc_process_lsens(uint8_t convert)
+void adc_process_lsens()
 {
     if (lsens_mode != LSENS_OUTPUT) {
         // do what needs to be done by me to defeat the light enemys
+        switch (lsens_mode) {
+            case LSENS_READING_IDLE: {
+                // prepare LED, wait a little bit
+                lsens_start();
+                adc_convert();
+                lsens_wait = lsens_coarse;
+
+                lsens_mode = LSENS_READING_START;
+
+                break;
+            }
+            case LSENS_READING_START: {
+                if (!lsens_wait) {
+                    // convert the LED
+                    adc_convert();
+
+                    lsens_mode = LSENS_READING_WAIT;
+                }
+
+                lsens_wait--;
+
+                break;
+            }
+            case LSENS_READING_WAIT: {
+                // read the light sensor value
+                adc_read();
+                lsens_stop();
+
+                // calculate adjustments
+                if (lsens_val > LSENS_COARSE_UP) {
+                    lsens_coarse++;
+                    if (lsens_coarse > 0x7f) lsens_coarse = 0x7f;
+                } else if (lsens_val < LSENS_COARSE_DOWN) {
+                    if (lsens_coarse) lsens_coarse--;
+                }
+
+                lsens_wait = 255 - lsens_coarse;
+
+                // wait a bit before doing it again
+                lsens_mode = LSENS_READING_TIMEOUT;
+
+                break;
+            }
+            case LSENS_READING_TIMEOUT: {
+                if (!lsens_wait) {
+                    // do it all again
+                    lsens_mode = LSENS_READING_IDLE;
+                }
+                lsens_wait--;
+            }
+        }
     }
 }
 
@@ -105,3 +161,8 @@ uint16_t adc_get_lsens()
 {
     return lsens_val;
 }
+
+uint8_t adc_get_lsens_coarse()
+{
+    return lsens_coarse;
+}
diff --git a/firmware/user/src/adc.h b/firmware/user/src/adc.h
index a0e4422..f10c9b5 100644
--- a/firmware/user/src/adc.h
+++ b/firmware/user/src/adc.h
@@ -10,17 +10,21 @@
 
 
 
-#define LSENS_DARK_THRESHOLD  0x7ff       // baseline minimum value reading achieved in darkness
+#define LSENS_DARK_THRESHOLD  0x7ff     // baseline minimum value reading achieved in darkness
 
 #define LSENS_PORT          GPIOA
 #define LSENS_A_PIN         GPIO_Pin_2
 #define LSENS_K_PIN         GPIO_Pin_3
 #define LSENS_ADC_CH        ADC_Channel_3
 
-enum {
+#define LSENS_COARSE_UP     0x680       // counts higher than this increase lsens_coarse, maximum 64
+#define LSENS_COARSE_DOWN   0x580       // counts lower than this decrease lsens_coarse, minimum 1
+
+enum lsens_mode {
     LSENS_READING_IDLE = 0,
     LSENS_READING_START,
     LSENS_READING_WAIT,
+    LSENS_READING_TIMEOUT,
     LSENS_OUTPUT = 0xff
 };
 
@@ -34,7 +38,10 @@ void adc_read();
 void adc_set_mode_lsens(uint8_t mode);
 uint8_t adc_get_mode_lsens();
 
-void adc_process_lsens(uint8_t convert);
+void adc_process_lsens();
+
+uint16_t adc_get_lsens();
+uint8_t adc_get_lsens_coarse();
 
 
 
diff --git a/firmware/user/src/ui.c b/firmware/user/src/ui.c
index 9324988..e17b5f6 100644
--- a/firmware/user/src/ui.c
+++ b/firmware/user/src/ui.c
@@ -4,6 +4,7 @@
 
 #include <stdint.h>
 
+#include "adc.h"
 #include "btn.h"
 #include "led.h"
 #include "ledprog_pep.h"
@@ -22,6 +23,15 @@
 
 
 
+static const uint8_t led_gc_map[] = {
+    48, 40, 34, 32,      // 0 = maybe outside, or really bright inside. 1-3 = indoors
+    30, 28, 27, 25,     // 4-7 = indoors
+    23, 21, 19, 18,     // 8-11 = indoors normal
+    17, 16, 15, 13,     // 12 = dimmest normal, 13 = darker, 14-15 darker still
+    11,  9,  7,  5,     // 16-19 = from night room light to computer light
+    0                   // 20 = outside mode turns off the LEDs
+};
+
 static uint8_t mode = MODE_RUN;
 static uint8_t tick = 0;
 
@@ -64,6 +74,8 @@ volatile uint8_t prog_run = 5;
 
 void ui_render()
 {
+    uint8_t w;
+
     tick++;
 
     switch (mode) {
@@ -80,6 +92,19 @@ void ui_render()
         }
     }
 
+    // set LED current based on brightness
+    w = adc_get_lsens_coarse();
+    if (w > 19) w = 19;
+    if (!w) {
+        // are you outside? why? it's too fucking hot
+        // we'll shut down when in the presence of big nuclear fire
+        if (adc_get_lsens() < 400) {
+            // yup, outside or in a spotlight at 3ft away or something
+            w = 20;
+        }
+    }
+    is31fl3729_set_global_current(FL3729_ADDR, led_gc_map[w]);
+
     // temporary: testing
 
     ledprog_pep[prog_run](tick);