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bootloader crc

 
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georpo



Joined: 18 Nov 2008
Posts: 278
Location: Athens, Greece.

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bootloader crc
PostPosted: Sun Dec 13, 2020 12:48 pm     Reply with quote
Hello,

I have seen that the loader_pcd checks each line checksum and then writes to program memory.

What if some lines are OK but some lines are bad data? Do I get a corrupt PIC?

In my tests, I send the hex file 2 times and write to 2 different locations of external flash, then compare the 2 files byte by byte and only if they are OK, I write them to the program memory.
This of course works but needs big flash etc.

How can I calculate the CRC of the hex file so I can send the hex file only once?
Code:

;DSPIC33FJ64GP804
;CRC=8C7D  CREATED="13-Dec-20 19:44"

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George.
PCM programmer



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Posts: 21708

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PostPosted: Sun Dec 13, 2020 12:57 pm     Reply with quote
See this thread for sample code:
http://www.ccsinfo.com/forum/viewtopic.php?t=58331
georpo



Joined: 18 Nov 2008
Posts: 278
Location: Athens, Greece.

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PostPosted: Sun Dec 13, 2020 1:14 pm     Reply with quote
Thanks PCM programmer!

I have the hex file in external flash.
Below are the last lines:
Code:

:1059E0008410020000000000F81202000000000015
:1059F000A415020000000000B8270200000000000B
:085A0000FFFF37000040FE002B
:00000001FF
;DSPIC33FJ64GP804
;CRC=8C7D  CREATED="13-Dec-20 19:44"


So, which is the last ASCII character that I will pass through the CRC16 code?
Is it the last 'F' before the 1st ';'?
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George.
georpo



Joined: 18 Nov 2008
Posts: 278
Location: Athens, Greece.

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PostPosted: Sun Dec 13, 2020 1:51 pm     Reply with quote
I got it.
It includes the ";DSPIC33FJ64GP804" line but not the CRC line.

It WORKS!

Thanks!!!!!!
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George.
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