spindle could not be stopped. Thanks again to Etienne for reporting

spindle_control.c

@@ -36,12 +36,16 @@ void spindle_run(int direction, uint32_t rpm)
 {
   if (direction != current_direction) {
     st_synchronize();
-    if(direction >= 0) {
+    if(direction) {
+      if(direction > 0) {
         SPINDLE_DIRECTION_PORT &= ~(1<<SPINDLE_DIRECTION_BIT);
       } else {
         SPINDLE_DIRECTION_PORT |= 1<<SPINDLE_DIRECTION_BIT;
       }
       SPINDLE_ENABLE_PORT |= 1<<SPINDLE_ENABLE_BIT;
+    } else {
+      SPINDLE_ENABLE_PORT &= ~(1<<SPINDLE_ENABLE_BIT);      
+    }
     current_direction = direction;
   }
 }