diff --git a/Core/Inc/PSE_unit.h b/Core/Inc/PSE_unit.h
index 82cd8ab..df9f277 100644
--- a/Core/Inc/PSE_unit.h
+++ b/Core/Inc/PSE_unit.h
@@ -54,6 +54,7 @@ typedef struct{
 // unit definition
 typedef struct{
   uint8_t enabled;
+  uint8_t reversed; // is the unit reversed (syringue pointing to the motor or away from it)
   pse_ports port; // physical port on which this unit is connected
   uint32_t flow; // flow (in µL.min-1)
   int32_t volume; // current volume dispensed (in µL)
diff --git a/Core/Inc/pse_stepper_planer.h b/Core/Inc/pse_stepper_planer.h
index 392e12d..3c875f0 100644
--- a/Core/Inc/pse_stepper_planer.h
+++ b/Core/Inc/pse_stepper_planer.h
@@ -19,8 +19,8 @@
 
 void pse_sp_start_axis(pse_stepper_conf* conf, pse_stepper_status* status);
 void pse_sp_stop_axis(pse_stepper_conf* conf);
-void pse_sp_set_dir(pse_stepper_conf* conf, int dir);
-int pse_sp_get_dir(pse_stepper_conf* conf);
+void pse_sp_set_dir(pse_unit* unit, int dir);
+int pse_sp_get_dir(pse_unit* unit);
 void pse_stepper_planer_tick(pse_unit* unit);
 void pse_sp_jog_speed(pse_stepper_conf* conf, pse_stepper_status* sta, int status);
 
diff --git a/Core/Src/PSE_unit_edit_screen.c b/Core/Src/PSE_unit_edit_screen.c
index f6357d4..0c129b6 100644
--- a/Core/Src/PSE_unit_edit_screen.c
+++ b/Core/Src/PSE_unit_edit_screen.c
@@ -23,6 +23,17 @@ static pse_unit* c_pse_unit;
 static uint8_t c_pse_units_num;
 static uint16_t ws_index;
 
+static void reverse_button_handler(lv_event_t * e){
+  lv_event_code_t code = lv_event_get_code(e);
+	lv_obj_t* button = lv_event_get_current_target(e);
+	lv_obj_t* label = lv_obj_get_child(button, 0);
+
+	c_pse_unit->reversed = !c_pse_unit->reversed;
+	lv_label_set_text(label, c_pse_unit->reversed?LV_SYMBOL_PREV:LV_SYMBOL_NEXT);
+	
+	save_units(c_pse_units, c_pse_units_num, ws_index);
+}
+
 static void back_button_handler(lv_event_t * e){
   lv_event_code_t code = lv_event_get_code(e);
 
@@ -192,7 +203,7 @@ static void jog_forward_button_handler(lv_event_t* e){
 
 	if(code == LV_EVENT_PRESSED) {
 		pse_sp_jog_speed(unit->stepper_conf, unit->stepper_status, 1);
-		pse_sp_set_dir(unit->stepper_conf, 1);
+		pse_sp_set_dir(unit, 1);
 		pse_sp_start_axis(unit->stepper_conf, unit->stepper_status);
 	}
 	else if(code == LV_EVENT_RELEASED){
@@ -207,7 +218,7 @@ static void jog_backward_button_handler(lv_event_t* e){
 
 	if(code == LV_EVENT_PRESSED) {
 		pse_sp_jog_speed(unit->stepper_conf, unit->stepper_status, 1);
-		pse_sp_set_dir(unit->stepper_conf, 0);
+		pse_sp_set_dir(unit, 0);
 		pse_sp_start_axis(unit->stepper_conf, unit->stepper_status);
 	}
 	else if(code == LV_EVENT_RELEASED){
@@ -287,6 +298,16 @@ void PSE_unit_edit_screen_Gen(pse_unit* units, pse_unit* c_unit, uint8_t units_n
 	lv_label_set_text(back_label, LV_SYMBOL_LEFT);
 	lv_obj_center(back_label);
 
+	// add a reverse button
+	lv_obj_t* reverse_button = lv_btn_create(top_menu);
+	lv_obj_set_size(reverse_button, lv_pct(10), lv_pct(100));
+	lv_obj_set_align(reverse_button, LV_ALIGN_TOP_RIGHT);
+	lv_obj_add_event_cb(reverse_button, reverse_button_handler, LV_EVENT_CLICKED, NULL);
+	// and it's button
+	lv_obj_t* reverse_label = lv_label_create(reverse_button);
+	lv_label_set_text(reverse_label, c_unit->reversed?LV_SYMBOL_PREV:LV_SYMBOL_NEXT);
+	lv_obj_center(reverse_label);
+
 	// grid layout for the widgets
 	lv_obj_t* units_grid = lv_obj_create(scr);
 	lv_obj_align_to(units_grid, top_menu, LV_ALIGN_OUT_BOTTOM_LEFT, 0, 0);
diff --git a/Core/Src/pse_stepper_planer.c b/Core/Src/pse_stepper_planer.c
index a84e972..60c868f 100644
--- a/Core/Src/pse_stepper_planer.c
+++ b/Core/Src/pse_stepper_planer.c
@@ -18,7 +18,7 @@ void pse_stepper_planer_tick(pse_unit* unit){
 	pse_stepper_status* s = unit->stepper_status;
 
 	HAL_GPIO_TogglePin(c->STEP_GPIO_Port, c->STEP_GPIO_Pin);
-	s->steps_counter += (pse_sp_get_dir(c)?1:-1) * HAL_GPIO_ReadPin(c->STEP_GPIO_Port, c->STEP_GPIO_Pin);
+	s->steps_counter += (pse_sp_get_dir(unit)?1:-1) * HAL_GPIO_ReadPin(c->STEP_GPIO_Port, c->STEP_GPIO_Pin);
 	if(s->stop_at_limit && s->steps_counter == s->stop_steps){
 		pse_sp_jog_speed(c, s, 0);
 		pse_sp_stop_axis(c);
@@ -36,12 +36,15 @@ void pse_sp_stop_axis(pse_stepper_conf* conf){
 	HAL_GPIO_WritePin(conf->EN_GPIO_Port, conf->EN_GPIO_Pin, GPIO_PIN_SET);
 }
 
-void pse_sp_set_dir(pse_stepper_conf* conf, int dir){
-	HAL_GPIO_WritePin(conf->DIR_GPIO_Port, conf->DIR_GPIO_Pin, dir);
+void pse_sp_set_dir(pse_unit* unit, int dir){
+	pse_stepper_conf* conf = unit->stepper_conf;
+	HAL_GPIO_WritePin(conf->DIR_GPIO_Port, conf->DIR_GPIO_Pin, unit->reversed?-dir:dir);
 }
 
-int pse_sp_get_dir(pse_stepper_conf* conf){
-	return HAL_GPIO_ReadPin(conf->DIR_GPIO_Port, conf->DIR_GPIO_Pin);
+int pse_sp_get_dir(pse_unit* unit){
+	pse_stepper_conf* conf = unit->stepper_conf;
+	int val = HAL_GPIO_ReadPin(conf->DIR_GPIO_Port, conf->DIR_GPIO_Pin);
+	return (unit->reversed?-val:val);
 }
 
 // https://en.wikipedia.org/wiki/Integer_square_root#Using_only_integer_division
@@ -100,7 +103,7 @@ void pse_stepper_planer_compute_sps(pse_unit* unit){
 
 void pse_sp_set_dir_all(pse_unit* units, int units_num, int dir){
 	for(int i = 0; i < units_num; i++){
-		pse_sp_set_dir(units[i].stepper_conf, dir);
+		pse_sp_set_dir(&units[i], dir);
 	}
 }