Electronic – Memory dump size does not match size of MTD partition

embeddedmicrocontrollernand-flashnon-volatile-memoryserial

Device with Linux embedded system on NAND flash memory. I did memory dump of some MTD devices partitions use serial console, from U-boot bootloader use available commands.
First I read MTD partition to address in the memory, then dumped memory from that address to the terminal window.
For example, MTD partition 0x01d60000-0x01e60000 : "FPAR" MTD partition size is 0x00100000 = 1048576 bytes

nand read 0x20000000 0x01d60000 0x00100000
NAND read: device 0 offset 0x1d60000, size 0x100000
1048576 bytes read: OK
md.b 0x20000000 0x00100000

Then saved log file with dump as text file, cut out extra stuff before and after the dump and coverted it to binary use 

xxd -r -p dump.txt dump.bin

Resulting bin file size 1,310,860 bytes is mismatching MTD partion size (1,048,576 bytes), its much larger. Is the problem related to hex data conversion or the dump process have errors? I understand that MTD partion size of 1048576 bytes is size assigned to the whole MTD partition, the actual data on partition takes much smaller space, the large space filled with hex 'ff' values. Additionally, can anyone advice good utility for hex to bin data conversion?

Edit: I tried the same steps with 64 bytes data size, and used Raw log session mode, after trimming extra stuff, the resulting ascii file is 318 bytes. After dump conversion, the bin size is 87 bytes.

20000000: a0 7c 4f fa 62 61 75 64 72 61 74 65 3d 31 31 35    .|O.baudrate=115
20000010: 32 30 30 00 65 74 68 61 64 64 72 3d 46 46 3a 46    200.ethaddr=FF:F
20000020: 46 3a 46 46 3a 46 46 3a 46 46 3a 46 46 00 6e 65    F:FF:FF:FF:FF.ne
20000030: 74 6d 61 73 6b 3d 32 35 35 2e 32 35 35 2e 32 35    tmask=255.255.25

Best Answer

Try: xxd -r -seek -0x20000000 dump.txt dump.bin

xxd -r -p expects input in plain hexadecimal format, without addresses or ASCII. xxd -r without -seek assumes that addresses are zero-based, and will seek or zero-pad its output to skip over regions not present in the dump (the first 0x20000000 = 536870912 bytes).

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