diff --git a/Core/Inc/pse_stepper_planer.h b/Core/Inc/pse_stepper_planer.h
index 28c479c..ff022c9 100644
--- a/Core/Inc/pse_stepper_planer.h
+++ b/Core/Inc/pse_stepper_planer.h
@@ -22,6 +22,8 @@ void pse_stepper_planer_tick(pse_unit* units, uint8_t units_num);
 void pse_sp_start_all(pse_unit* units, int unit_num);
 void pse_sp_stop_all(pse_unit* units, int unit_num);
 
+void pse_sp_set_timer(TIM_HandleTypeDef* tim);
+
 void pse_stepper_planer_compute_sps(pse_unit* unit);
 
 #endif /* INC_PSE_STEPPER_PLANER_H_ */
diff --git a/Core/Src/home_screen.c b/Core/Src/home_screen.c
index 6428e80..c3d565e 100644
--- a/Core/Src/home_screen.c
+++ b/Core/Src/home_screen.c
@@ -47,11 +47,16 @@ static void unit_widget_enabled_handler(lv_event_t * e){
 		lv_obj_t* button = lv_event_get_current_target(e);
 		lv_obj_t* label = lv_obj_get_child(button, 0);
 		lv_state_t state = lv_obj_get_state(button);
+
+
+		pse_unit* unit = lv_event_get_user_data(e);
 		if(state & LV_STATE_CHECKED){
-			lv_label_set_text(label, LV_SYMBOL_CLOSE);
+			lv_label_set_text(label, LV_SYMBOL_OK);
+			unit->enabled = 0;
 		}
 		else{
-			lv_label_set_text(label, LV_SYMBOL_OK);
+			lv_label_set_text(label, LV_SYMBOL_CLOSE);
+			unit->enabled = 1;
 		}
   }
 }
@@ -96,11 +101,11 @@ static lv_obj_t* PSE_unit_widget(lv_obj_t* parent, pse_unit* pse_unit){
 	lv_obj_t* enabled = lv_btn_create(cont);
 	lv_obj_t* enabled_label = lv_label_create(enabled);
 	lv_obj_set_width(enabled, lv_pct(100));
-  lv_obj_add_flag(enabled, LV_OBJ_FLAG_CHECKABLE);
-	lv_obj_add_event_cb(enabled, unit_widget_enabled_handler, LV_EVENT_ALL, NULL);
+    lv_obj_add_flag(enabled, LV_OBJ_FLAG_CHECKABLE);
+	lv_obj_add_event_cb(enabled, unit_widget_enabled_handler, LV_EVENT_ALL, pse_unit);
 	lv_obj_set_flex_grow(enabled, 1);
 	lv_obj_center(enabled_label);
-	lv_label_set_text(enabled_label, LV_SYMBOL_OK);
+	lv_label_set_text(enabled_label, LV_SYMBOL_CLOSE);
 	if(!pse_unit->enabled){
 		lv_obj_add_state(enabled, LV_STATE_CHECKED);
 		lv_event_send(enabled, LV_EVENT_VALUE_CHANGED, NULL);
diff --git a/Core/Src/main.c b/Core/Src/main.c
index 4bbc6a7..c36cfd2 100644
--- a/Core/Src/main.c
+++ b/Core/Src/main.c
@@ -256,7 +256,7 @@ int main(void)
   ADS7843_Init(&Touch_Def);
 
   load_units(pse_units, pse_syringes, pse_stepper_confs, PSE_UNITS_NUM);
-  HAL_TIM_Base_Start_IT(&htim4);
+  pse_sp_set_timer(&htim4);
   Home_Screen_Gen(pse_units, PSE_UNITS_NUM);
   /* USER CODE END 2 */
 
diff --git a/Core/Src/pse_stepper_planer.c b/Core/Src/pse_stepper_planer.c
index a60b828..e9afc41 100644
--- a/Core/Src/pse_stepper_planer.c
+++ b/Core/Src/pse_stepper_planer.c
@@ -11,6 +11,9 @@
 
 #include "pse_stepper_planer.h"
 
+static int units_running = 0; // counter of currently running units, to disable interrupts when unnecessary
+static TIM_HandleTypeDef* htim; // main interrupt timer handle
+
 void pse_stepper_planer_tick(pse_unit* units, uint8_t units_num){
 	for(int i = 0; i < units_num; i++){
 		pse_stepper_conf* c = units[i].stepper_conf;
@@ -30,9 +33,20 @@ void pse_stepper_planer_tick(pse_unit* units, uint8_t units_num){
 }
 
 void pse_sp_start_axis(pse_stepper_conf* conf){
+	if(HAL_GPIO_ReadPin(conf->EN_GPIO_Port, conf->EN_GPIO_Pin) == GPIO_PIN_SET){
+		if(units_running == 0)
+			HAL_TIM_Base_Start_IT(htim);
+		units_running++;
+	}
+
 	HAL_GPIO_WritePin(conf->EN_GPIO_Port, conf->EN_GPIO_Pin, GPIO_PIN_RESET);
 }
 void pse_sp_stop_axis(pse_stepper_conf* conf){
+	if(HAL_GPIO_ReadPin(conf->EN_GPIO_Port, conf->EN_GPIO_Pin) == GPIO_PIN_RESET){
+		units_running--;
+		if(units_running == 0)
+			HAL_TIM_Base_Stop_IT(htim);
+	}
 	HAL_GPIO_WritePin(conf->EN_GPIO_Port, conf->EN_GPIO_Pin, GPIO_PIN_SET);
 }
 
@@ -51,14 +65,24 @@ void pse_stepper_planer_compute_sps(pse_unit* unit){
 
 
 void pse_sp_start_all(pse_unit* units, int units_num){
+	HAL_TIM_Base_Start_IT(htim);
+	units_running = units_num;
+
 	for(int i = 0; i < units_num; i++){
 		if(units[i].enabled)
 			pse_sp_start_axis(units[i].stepper_conf);
 	}
 }
 void pse_sp_stop_all(pse_unit* units, int units_num){
+	HAL_TIM_Base_Stop_IT(htim);
+	units_running = 0;
+
 	for(int i = 0; i < units_num; i++){
 		if(units[i].enabled)
 			pse_sp_stop_axis(units[i].stepper_conf);
 	}
 }
+
+void pse_sp_set_timer(TIM_HandleTypeDef* tim){
+	htim = tim;
+}