crc16 of the ds2431 - Githubissues

orgua / OneWireHub

OneWire slave device emulator

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crc16 of the ds2431 #9

Closed orgua closed 7 years ago

orgua commented 7 years ago

hi @j-langlois

could you give me hint where you got the start-value of the crc. the datasheet is missing some information. and does not mention anything else than flush/reset the crc16-input. i have extended the device and everythings works, except the eprom-mode. i had trouble using your start-value and more luck with just 0. ds2433 is very similar but doesn't mention any information either.

j-langlois commented 7 years ago

Hello orgua, Honestly, I do not have a clue why no start value is mentioned in the documentation. Basically, I made several writes to the scratchpad of an actual DS2431 and noted what the chip gave me. Then, I ran every start value in the code to determine which one would match the result given by the chip. However, this might very well be version specific. I am using DS2431Gs.

What issues are you experiencing with the eeprom mode and master are you using ?

orgua commented 7 years ago

oh well, so this could be a crc-collision. did you begin with 0x0000 for your brute-force-calculation? It should work. the DS9490 reads it everytime. using the ds2431-slave with the current code and a ds9490R as a master i get:

changing the pages and upper control-bytes work as expected when no matching write protection is set
using/changing pages in EEPROM-MODE gives me a bad CRC and no data seems to be written/cleared

orgua commented 7 years ago

ok, EPROMs seem to initialize the CRC with zero and not with some magic-byte. my master ds9490 is ok with that. will close this