Invalid Checksum of first 512 UU-encoded bytes

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Invalid Checksum of first 512 UU-encoded bytes

Contributor II


I have made a UU-encoding console application in c# and used flashMagic tool as reference to confirm if i am doing everything right. I need it to write on LPC1767 microcontroller. The only issue i am facing is that the checksum of first 512 bytes are not valid, what i am getting is 34964 whereas what flashmagic provides is 35644, according to the raw hex is to be added with each other to make a valid checksum, but in my case only first checksum is not valid rather then this all the checksums are valid. As i am new to this field i need to know where i am wrong and how will i be able to fix it.

First 512 bytes are


Thank You,



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NXP TechSupport
NXP TechSupport


I suggest following the AN 5.3  Writing to RAM section, take use the command from AN to test if the system can work as expected. thus we can verify if the system functions well with checksum


Data is sent and received in UUencoded format .  The chip is only recogonized the checksum that is generated by adding raw data (before UU-encoding) bytes.

Regarding how the FlashMagic handle checksum inside, we would suggest you contact Welcome - EmSA  who is FlashMagic producer and their forum:

Flash Magic Forum - Index 

Have a great day,
Jun Zhang

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