rpm function added for part 1

src/rotary_encoder_driver.cpp

@@ -44,6 +44,10 @@ void RotaryEncoderDriver::update_delta() {
 
 float RotaryEncoderDriver::count_per_sec() {
     return delta / (256.0f * 0.0001f);
+} 
+
+float RotaryEncoderDriver::rpm() {
+    return (count_per_sec() * 60) / 1050.0;
 }