move DATA_SIZE to global

rotator/rotator.ino

@@ -51,6 +51,11 @@ uint8_t lastClk = HIGH;
 byte valueBuffer[VALUE_BUFFER] = { 0 };
 uint8_t readerPos, writerPos = 0;
 
+// ringbuffer of display data
+struct {
+  
+}
+
 void addValue(uint8_t value) {
   valueBuffer[writerPos++] = value;