readData method
Implementation
@override
List<int> readData(int length) {
// generate a list of length + 1 and the first element is
// `pn532SpiDataRead` and the rest is filled with zeros
final List<int> frame = [pn532SpiDataRead, ...List.filled(length, 0)];
sleep(const Duration(milliseconds: 5));
// transfer the list and read into it at the same time
final List<int> response = readWriteHelper(frame);
// get the response of the frame (without the added first byte) and return it
return response.sublist(1);
}