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635 - CRC - perl

vthinsel

New member
Hello !

I have tried the perl code included in the data sheet, and here is the output:

~/dev/lcdlib/TestsStandalone> ./cftest.pl
A CRC of Packet (800105) Should Equal (5584)
ffff
b24c
b959
fe7e
ba0d
eadc
7a25
85da

So I get 85da instead of 5584.

Before I go to the cellar to get my old lessons on data integrity could someone tell me if this example should work ?

I'm getting confused between ord, char, hexa, decimal, carcters...
when saying type '80', it is 0x80, correct ? 10000000 in binary ?
What should be the CRC for 0x80 ?

Thanks !

Vincent
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CF Tech

Administrator
Aye, I couldn't PERL meself out of a wet paper bag. The person that submitted the PERL example to us stated it worked, but beyond that . . .

Here are a couple of debugger screenshots of packets showing the exact byte order, right before they go out the port. Unfortunately, they are for the CFA-633, and the commands 7 & 8 used as examples have been deprecated in the CFA-635.

http://www.crystalfontz.com/backlight/633_test_packet.pdf
 

vthinsel

New member
Thanks for the update and the nice snapshot. I'll also check on the wintest app when I get the 635.

The CRC is calculated the same way on 633 and 635 ?

Vincent.
 

vthinsel

New member
CF Tech said:
Ok.

I really don't see how the perl example in the appendix can work.
The value 80 should be 0x80, as it is hexa, and not decimal
Moreover using the concatenation operato r "." generates 6 cars, and not 3 bytes: 800105.

All in all, I got the example to work succesfully by doing this:
my $type = 0x00;
my $length = 0x02;
my $data = 0xff;
my $packet = pack 'C4',$type,$length,$data,$data;

Thsi is a ping packet, with 2 bytes set to 0xff.
The calculated CRC for this packet is: b9de, as the packet debugger tells me. So now, I need to make the packet generator more versatile.

Vincent.
 
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