properly Calculating connect macro checksum

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Sil
Posts: 38
Joined: Mon Feb 13, 2006 6:03 am

properly Calculating connect macro checksum

Post by Sil »

hi, i have df, and need the calculate the checksum for the connect command, how do i go about doing that to get the checksum to add to the end
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Mangus
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Post by Mangus »

Depends on the vehicle. In the latest builds, TunerPro will calculate this for you, provided your vehicle uses one of the built-in calculations.
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robertisaar
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Post by robertisaar »

i just used the checksum that TPV4(or V5, i'm not really sure which did it) calculated when i imported the ADS... though i'm not sure of which of the options GM ECMs do...
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Mangus
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Post by Mangus »

GM OBDI vehicle command checksum is 1's compliment of the preceding bytes.

-M
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robertisaar
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Post by robertisaar »

really? because if i set to 1's compliment i get a checksum value exactly 1 below what the previous checksum was calculated as after i remove it, while 2's compliment gives me the same number as the checksum that i removed...
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Mangus
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Post by Mangus »

robertisaar wrote:really? because if i set to 1's compliment i get a checksum value exactly 1 below what the previous checksum was calculated as after i remove it, while 2's compliment gives me the same number as the checksum that i removed...
You are correct; 2's compliment. Sorry for the missed key.
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