I'm still puzzled about the format for the packet header. Here are three headers:
7E 41 0E 1C (ack-requested header) 7E 40 0E (ack reply header) 7E 42 01 (no-ack header) In the 1st message there's a 1C byte which http://cents.cs.berkeley.edu/tinywiki/index.php/Packetizer_Protocol calls "packet cookie". In the 2nd packet, the packet cookie byte isn't present (the 0E is the "prefix byte"). In the 3rd packet the packet cookie is 01. So, what is this "packet cookie" and how is it used in messaging? Is it some kind of sequence number? In any case, where should I have looked to get the answer? Thanks, Bill ------------------------- Bill Leal Computer Science and Engineering The Ohio State University 395 Dreese Laboratories 2015 Neil Avenue Columbus, OH 43210-1277 Fax: +1-815-301-8202 > -----Original Message----- > From: Ben Buckner [mailto:[EMAIL PROTECTED] > Sent: Monday, April 23, 2007 5:36 PM > To: [email protected]; [EMAIL PROTECTED] > Subject: RE: [Tinyos-help] tmote message format > > Bill- > > >From the legendary Octavetech protocol document that you linked: > > "P_PACKET_ACK (0x41) - User packet. ACK required. Includes a prefix byte. > Receiver must send a P_ACK response with prefix byte as contents." > > Regards, > Ben B. > > > Date: Mon, 23 Apr 2007 13:55:54 -0400 > > From: "Bill Leal" <[EMAIL PROTECTED]> > > Subject: [Tinyos-help] tmote message format > > To: <[email protected]> > > Message-ID: <[EMAIL PROTECTED]> > > Content-Type: text/plain; charset="us-ascii" > > > > I'm trying to understand the packet format of a PC app that interacts > with > a > > tmote; the format for messages to the tmote seem to contain an > additional > byte. > [...] > > I think the address (FF FF) should begin with the 9th byte but it is the > > 10th. What puzzles me is the 4th byte (1C); why is it there? This is > > different than the packet format I'm getting from the mote: > [...] > > I note that the message type to the mote is ack-requested (41), which > > perhaps accounts for the extra byte. But I haven't been able to locate > any > > doc on that. >
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