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1

You can read data with : status = mfrc522.MIFARE_Read(blockNum, readBlockData, &bufferLen); and write data by: status = mfrc522.MIFARE_Write(blockNum, blockData, 16); However, there's a lot more to it, so check examples of the RFID library, or this external articles: https://www.electronicshub.org/write-data-to-rfid-card-using-rc522-rfid/ https://...


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The double data type is almost universally 8-bytes long, so you could simply #if !__AVR__ # define HAS_64_BIT_DOUBLE #endif Gcc provides a more specific macro though: __SIZEOF_DOUBLE__, which has the same value as sizeof(double). But I do not know whether it is provided by other compilers.


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