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CRC TMS3705

Juliana Araujo

Prodigy 70 points

Other Parts Discussed in Thread: TMS3705

Good afternoon,

I would want to know how do for calculate the code of CRC. And when TMS3705 send me the code of transponder it send invert the order and bits of code, I would want to know if for calculate the CRC of mensage I will calculate with the mensage the same way and order how it send to me?

Thanks for help,

Juliana Araujo

over 14 years ago

0 Josh Wyatt over 14 years ago

TI__Guru* 91206 points

Juliana -

it depends on the tag being used, but in both cases i can think of here the CRC is reverse CCITT-16 with either a start value of 0x0000 or 0x3791. Please see slides 22-29 of the attachment here where this tag responds using 0x3791 as start value.

1070.TMS37157 PaLFI_Technical_Training_03_29_2010.ppt

0 Juliana Araujo over 14 years ago in reply to Josh Wyatt

Prodigy 70 points

Josh,

OK, I see the slides, but I what is reverse CCITT-16 ? What's the diference about the normal CCITT-16 and reverse CCITT-16 ? And how I can calculate this.

0 Josh Wyatt over 14 years ago in reply to Juliana Araujo

TI__Guru* 91206 points

Juliana -

sorry for the delay - i took some time off - anyway - the polynomial to use here is: $x 16 + x 12 + x 5 + 1$

This is pretty good app note on the CRC-16, for your reference ==> 1524.CRC16.pdf

0 Juliana Araujo over 14 years ago in reply to Josh Wyatt

Prodigy 70 points

Josh Wyatt,

I found a software that calculate CRC-16 for TMS3705, and I'm using it now.

Thanks for your help.

0 Rosemarie Sheehy over 9 years ago in reply to Juliana Araujo

Prodigy 20 points

Hi Josh

I am now trying to calculate CRC-16 for TMS3705, can you give more information regarding the software that you found please.

0 Josh Wyatt over 9 years ago in reply to Rosemarie Sheehy

TI__Guru* 91206 points

attached is a CRC GUI that we use to double check firmware:

CRCCalculator.zip

0 Rosemarie Sheehy over 9 years ago in reply to Josh Wyatt

Prodigy 20 points

Thanks for the reply Josh.

Using the link you sent I can verify that the CRC I expect is correct.

But I am trying to calculate this CRC now, using the file attached as reference I cannot calculate the correct CRC

unsigned char testStr[] = "F568DC0C57F58095";

bcc = calc_BCC(8,0x0000,testStr);

bcc= 14883 (39F1)

I would have expected the CRC C2D5

Thanks for your help

CRC Algorithm.doc