CRC15 with LabVIEW

[cyongjed]

Hi LabVIEW Community,

Just to check if anyone did do a CRC15 VI calculation before using LabVIEW? Have been searching through the forums but didn't find any. I am currently tasked to develop a VI to calculate the Packet Error Code for the LTC6811 Chipset developed by Linear Technologies but I realize the Packet Error Code (PEC) is the same as the CAN bus for the first 15 bits, the only difference is the last bit which there is a 0 attached for the Final PEC. I have attached screenshots obtained from the datasheet below

Can any experts advise me on this situation, please?

Thanks!

[GerdW]

Hi cyongjed,

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@cyongjed wrote:

Can any experts advise me on this situation, please?

What have you tried and where are you stuck?

Why don't you attach your VI?

The manual is rather clear: you can handle boolean values in LabVIEW and there is a XOR function available…

[cyongjed]

Hi Gerd,

Thank you for the response.

I have tried it out with a design of my own version of the VI, and have attached it in the reply. I am currently having issues getting the correct output for the PEC. For example, the PEC of 0x0001 (input DIN) will be computed as 0x3D6E as the final result, but I am getting otherwise. 

Attached the bitwise operation for this in the post:

Regards,

cyongjed

[crossrulz · Accepted solution]

Here's what I came up with.  Hopefully, you have more test vectors to try this on to make sure it works.

NOTE: The extra Rotate Left With Carry is to get bit 14 from the PEC (a 15-bit CRC is kind of weird).

[cyongjed]

Hi Cross,

Thank you for the assistance given.

I have a doubt here, why did you use 0x4599 instead of 0xC599? I don't really get this.

Hope to hear from you soon!

Regards,

cyongjed

[crossrulz]

You always ignore the top item in the polynomial, in this case the x^15.  In this case, it does not really matter since bit 15 is not used in the CRC.