ext_Flash_write_sample erase sector optimization: The previous function erased a sector while writing sample data causing a delay of up to 200ms. The new implementation checks at the end of a write sample call if we are close to a sector end. In case we are a erase sector command will be send to the flash for the next sector. At the time of the next sample write (2 seconds later) the next sector is already erased and no busy wait of 200ms is needed => max write time for samples is not less than 5ms.