I'm having some problems calculating a checksum for a DNP3 link using Digest::CRC.
The spec says it's a 2 octet CRC based on the polynomial X^16 + X^13 + X^12 + X^11 + X^10 + X^8 + X^6 + X^5 + X^2 + 1. It's also inverted and put in the data block LSB first.
With Perl's Digest package, I set up the algorithm as: 
my $ctx = Digest::CRC->new(width=>16, init=>0, xorout=>0xffff,
  refin=>1, refout=>1, poly=>0x3d65, cont=>0xea82);

$ctx->add(0x05);
$ctx->add(0x64);
$ctx->add(0x05);
$ctx->add(0xF2);
$ctx->add(0x01);
$ctx->add(0x00);
$ctx->add(0x00);
$ctx->add(0x00);

my $x=$ctx->digest;
printf("x=%04x\n",$x);

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The example in the spec shown for the header: 05 64 05 F2 01 00 00 00 the checksum should be 52 0C. I get x=91fc. I've tried playing with all the parameters but can't seem to get it to come out. Any suggestions?

In reply to Using Digest::CRC to calculate DNP3 checksums by wdtj

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