JBM
Joined: 12 May 2004
Posts: 54
Location: edinburgh, Scotland
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| Wake on LAN - sending the frame from a PIC |
 Posted: Mon Dec 26, 2005 11:11 am |
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I've recently found an application where it would be handy to have a PIC based device send Wake-On-Lan frames to PCs. I thought it would be very straightforward, but I've run into a problem (or two).
I'm using the PICDEM.net board from MCHP, and the CCS port of their stack.
My problem is that when I send my data as a frame and use Ethereal to view it, more is data is being sent than I want to be. More specifically, it assumes the frame I send is a multicast packet of IP type (i think), then tacks the data I want on to the end. I want only the bytes I send using MACPut to be sent.
I'll post the code and a frame it sends below. I'm sure it's something pretty obvious, but since i've never gone down to the MAC layer beofre, it's not so obvious to me!
| Code: | void MagicPacket()
{
int8 to[6]={0x00,0x12,0x3F,0xD0,0x97,0xF8};
int8 i;
MACPut(to[0]); //to
MACPut(to[1]);
MACPut(to[2]);
MACPut(to[3]);
MACPut(to[4]);
MACPut(to[5]);
MACPut(MY_MAC_BYTE1); //from
MACPut(MY_MAC_BYTE2);
MACPut(MY_MAC_BYTE3);
MACPut(MY_MAC_BYTE4);
MACPut(MY_MAC_BYTE5);
MACPut(MY_MAC_BYTE6);
MACPut(0x00);
MACPut(0xFE);
MACPut(0xFF);
MACPut(0xFF);
MACPut(0xFF);
MACPut(0xFF);
MACPut(0xFF);
MACPut(0x00);
for(i=0; i<16; i++){
MACPut(to[0]); //to
MACPut(to[1]);
MACPut(to[2]);
MACPut(to[3]);
MACPut(to[4]);
MACPut(to[5]);
}
MACFlush();
}
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Here's what etheral says is being sent.
| Code: |
0000 ff ff ff ff ff ff 46 20 46 41 54 20 08 00 45 00 ......F FAT ..E.
0010 01 14 01 76 00 00 64 11 54 64 00 00 00 00 ff ff ...v..d.Td......
0020 ff ff 00 44 00 43 01 00 00 00 00 12 3f d0 97 f8 ...D.C......?...
0030 46 20 46 41 54 20 00 fe ff ff ff ff ff 00 00 12 F FAT ..........
0040 3f d0 97 f8 00 12 3f d0 97 f8 00 12 3f d0 97 f8 ?.....?.....?...
0050 00 12 3f d0 97 f8 00 12 3f d0 97 f8 00 12 3f d0 ..?.....?.....?.
0060 97 f8 00 12 3f d0 97 f8 00 12 3f d0 97 f8 00 12 ....?.....?.....
0070 3f d0 97 f8 00 12 3f d0 97 f8 00 12 3f d0 97 f8 ?.....?.....?...
0080 00 12 3f d0 97 f8 00 12 3f d0 97 f8 00 12 3f d0 ..?.....?.....?.
0090 97 f8 00 12 3f d0 97 f8 00 12 3f d0 97 f8 00 12 ....?.....?.....
00a0 3f d0 97 f8 46 20 46 41 54 20 00 fe ff ff ff ff ?...F FAT ......
00b0 ff 00 00 12 3f d0 97 f8 00 12 3f d0 97 f8 00 12 ....?.....?.....
00c0 3f d0 97 f8 00 12 3f d0 97 f8 00 12 3f d0 97 f8 ?.....?.....?...
00d0 00 12 3f d0 97 f8 00 12 3f d0 97 f8 00 12 3f d0 ..?.....?.....?.
00e0 97 f8 00 12 3f d0 97 f8 00 12 3f d0 97 f8 00 12 ....?.....?.....
00f0 3f d0 97 f8 00 12 3f d0 97 f8 00 12 3f d0 97 f8 ?.....?.....?...
0100 00 12 3f d0 97 f8 00 12 3f d0 97 f8 00 12 3f d0 ..?.....?.....?.
0110 97 f8 00 12 3f d0 97 f8 46 20 46 41 54 20 00 fe ....?...F FAT ..
0120 ff ff ..
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I can see the data I want sent withing the above block:
| Code: |
00 12 3f d0 97 f8 ...D.C......?...
0030 46 20 46 41 54 20 00 fe ff ff ff ff ff 00 00 12 F FAT ..........
0040 3f d0 97 f8 00 12 3f d0 97 f8 00 12 3f d0 97 f8 ?.....?.....?...
0050 00 12 3f d0 97 f8 00 12 3f d0 97 f8 00 12 3f d0 ..?.....?.....?.
0060 97 f8 00 12 3f d0 97 f8 00 12 3f d0 97 f8 00 12 ....?.....?.....
0070 3f d0 97 f8 00 12 3f d0 97 f8 00 12 3f d0 97 f8 ?.....?.....?...
0080 00 12 3f d0 97 f8 00 12 3f d0 97 f8 00 12 3f d0 ..?.....?.....?.
0090 97 f8 00 12 3f d0 97 f8 00 12 3f d0 97 f8
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The other problem is that i'm not sure how to generate a frame check - I have a feeling it's done for me, but I'd like someone who knows to confirm it to me! |
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