diff --git a/stereo_mix/drivers/leds.h b/stereo_mix/drivers/leds.h
new file mode 100644
index 0000000..21f0082
--- /dev/null
+++ b/stereo_mix/drivers/leds.h
@@ -0,0 +1,46 @@
+#pragma once
+
+#include "stm32f0xx_hal_gpio.h"
+#include <stm32f0xx_hal.h>
+
+const uint8_t kNumChannels = 4;
+
+static const uint16_t kGpioPins[] = { GPIO_PIN_7, GPIO_PIN_15, GPIO_PIN_13, GPIO_PIN_14 };
+static GPIO_TypeDef* kGpioPorts[] = { GPIOB, GPIOB, GPIOF, GPIOF };
+
+class Leds {
+  public:
+  Leds()
+  {
+    GPIO_InitTypeDef gpioInit;
+    for (size_t i = 0; i < kNumChannels; i++) {
+      gpioInit.Mode = GPIO_MODE_OUTPUT_PP;
+      gpioInit.Pin = kGpioPins[i];
+      gpioInit.Pull = GPIO_NOPULL;
+      gpioInit.Speed = GPIO_SPEED_FREQ_MEDIUM;
+      HAL_GPIO_Init(kGpioPorts[i], &gpioInit);
+    }
+  }
+  void Write()
+  {
+    pwm_counter += 2;
+
+    for (size_t i = 0; i < kNumChannels; i++) {
+      if (intensities[0] && intensities[i] >= pwm_counter) {
+        HAL_GPIO_WritePin(kGpioPorts[i], kGpioPins[i], GPIO_PIN_SET);
+      } else {
+        HAL_GPIO_WritePin(kGpioPorts[i], kGpioPins[i], GPIO_PIN_RESET);
+      }
+    }
+  }
+  void set_intensity(uint8_t channel, uint8_t intensity)
+  {
+    if (channel >= kNumChannels)
+      return;
+    intensities[channel] = intensity;
+  }
+
+  private:
+  uint8_t pwm_counter;
+  uint8_t intensities[kNumChannels];
+};
diff --git a/stereo_mix/drivers/peripherals.c b/stereo_mix/drivers/peripherals.c
index 38c43e9..3379a21 100644
--- a/stereo_mix/drivers/peripherals.c
+++ b/stereo_mix/drivers/peripherals.c
@@ -3,6 +3,7 @@
 ADC_HandleTypeDef hadc1 = { .Instance = ADC1 };
 DMA_HandleTypeDef hdma1_channel1 = { .Instance = DMA1_Channel1 };
 SPI_HandleTypeDef hspi1 = { .Instance = SPI1 };
+TIM_HandleTypeDef htim3 = { .Instance = TIM3 };
 
 void DMA1_Channel1_IRQHandler(void)
 {
@@ -12,3 +13,7 @@ void ADC1_IRQHandler(void)
 {
   HAL_ADC_IRQHandler(&hadc1);
 }
+void TIM3_IRQHandler()
+{
+  HAL_TIM_IRQHandler(&htim3);
+}
diff --git a/stereo_mix/drivers/peripherals.h b/stereo_mix/drivers/peripherals.h
index b762322..12aca5e 100644
--- a/stereo_mix/drivers/peripherals.h
+++ b/stereo_mix/drivers/peripherals.h
@@ -5,3 +5,5 @@
 extern ADC_HandleTypeDef hadc1;
 extern DMA_HandleTypeDef hdma1_channel1;
 extern SPI_HandleTypeDef hspi1;
+extern TIM_HandleTypeDef htim3;
+
diff --git a/stereo_mix/stereo_mix.cc b/stereo_mix/stereo_mix.cc
index e3bf74d..4f5003f 100644
--- a/stereo_mix/stereo_mix.cc
+++ b/stereo_mix/stereo_mix.cc
@@ -1,7 +1,9 @@
 #include "drivers/adc.h"
 #include "drivers/dac.h"
+#include "drivers/leds.h"
 #include "drivers/peripherals.h"
 #include "resources.h"
+#include "stm32f0xx_hal_rcc.h"
 #include <stm32f0xx_hal.h>
 
 using namespace stereo_mix;
@@ -11,10 +13,11 @@ Dac dacs[8] = {
   { GPIOA, GPIO_PIN_8 }, { GPIOA, GPIO_PIN_9 }, { GPIOA, GPIO_PIN_10 }, { GPIOA, GPIO_PIN_11 }
 };
 Adc adc;
+Leds leds;
 
 // Default interrupt handlers.
 extern "C" {
-void NMI_Handler() {}
+void NMI_Handler() { }
 void Error_Handler()
 {
   while (1)
@@ -40,9 +43,9 @@ void UsageFault_Handler()
   while (1)
     ;
 }
-void SVC_Handler() {}
-void DebugMon_Handler() {}
-void PendSV_Handler() {}
+void SVC_Handler() { }
+void DebugMon_Handler() { }
+void PendSV_Handler() { }
 
 // called every 1ms
 void SysTick_Handler()
@@ -85,6 +88,27 @@ void HAL_ADC_ConvCpltCallback(ADC_HandleTypeDef* hadc)
 {
   adc.OnDMATransferComplete();
 }
+void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef* htim) // called with 1kHz (OPTIMIZE!) the display should get its own spi bus
+{
+  if (htim != &htim3) {
+    return;
+  }
+  leds.Write();
+}
+}
+
+void Init(void)
+{
+  HAL_NVIC_SetPriority(TIM3_IRQn, 0, 0);
+  HAL_NVIC_EnableIRQ(TIM3_IRQn);
+  __HAL_RCC_TIM3_CLK_ENABLE();
+  htim3.Init.Prescaler = 24;
+  htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
+  htim3.Init.Period = 128; // 8kHz
+  htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
+  htim3.Init.RepetitionCounter = 0;
+  HAL_TIM_Base_Init(&htim3);
+  HAL_TIM_Base_Start_IT(&htim3);
 }
 
 int main(void)
@@ -93,6 +117,10 @@ int main(void)
   SystemClock_Config();
   __HAL_RCC_SYSCFG_CLK_ENABLE();
   __HAL_RCC_PWR_CLK_ENABLE();
+  __HAL_RCC_GPIOB_CLK_ENABLE();
+  __HAL_RCC_GPIOF_CLK_ENABLE();
+
+  Init();
 
   while (true) {
     for (int i = 0; i < 4; i++) {
@@ -108,7 +136,7 @@ int main(void)
 
       CONSTRAIN(pan, 0, (1 << 12) - 1);
       CONSTRAIN(vol, 0, (1 << 12) - 1);
-
+      leds.set_intensity(i, vol >> 4);
       value_l = (lut_left_sin_pan[pan] * lut_linear_to_exp[vol]) >> 16;
       value_r = (lut_right_cos_pan[pan] * lut_linear_to_exp[vol]) >> 16;
 
diff --git a/stmlib b/stmlib
index 027f064..0c9129a 160000
--- a/stmlib
+++ b/stmlib
@@ -1 +1 @@
-Subproject commit 027f064b70c6fd3d137ea530c446609a1da5a564
+Subproject commit 0c9129ad08236a1987b0d81d1019b947a247a9ff