fast display update (without refresh)

src/main.cpp

@@ -263,7 +263,12 @@ void displayValues() {
   char timeStr[40];
   getTime(timeStr, sizeof(timeStr), "%d. %b %Y  %H:%M:%S");
 
-  display.setFullWindow();
+
+  if (display.epd2.hasFastPartialUpdate) {
+    display.setPartialWindow(0, 0, display.width(), display.height());
+  } else {
+    display.setFullWindow();
+  }
   display.firstPage();
   do
   {