View Full Version : Counting using delta_t and packet_num

06-23-2002, 11:19 PM
Posted by Kai Zhao at 2/5/2001 9:18 PM EST

Student on team #686, Botler & Associates, from Linganore High School, Frederick MD and NASA/GFSC and Smiths Industries.

I have read previous postings on how to do timing but I don't understand the exact data coming out of delta_t and packet_num. I would love to play around with delta_t and packet_num but my team doesn't have a working robot to test with.

From what I understand, delta_t is the time it took to complete the last? loop in milliseconds?
packet_num is a packet counter, it increments in 1's about every 40ms? It resets itself to zero after it reaches 254 or 255? Right? Wrong? Way off?


06-23-2002, 11:19 PM
Posted by Joe Johnson at 2/5/2001 10:11 PM EST

Engineer on team #47, Chief Delphi, from Pontiac Central High School and Delphi Automotive Systems.

In Reply to: Counting using delta_t and packet_num
Posted by Kai Zhao on 2/5/2001 9:18 PM EST:

My understanding is that delta_t is the number of data
packets MISSED by your PBASIC program. This occurs
when your code takes longer than the time it takes to
send another data packet (some say 40ms but I thought
it was 25ms -- these are very similar numbers and I can
never hold them straight in my head -- either it is 40
Hz and 25msec or it is 25Hz and 40msec -- somebody help
me out).

Packet number is an index that tells you the index of
the packet of data you just got. It increases by one
each time the OI sends a data packet and it wraps
around every
255 packets.

These two bytes carry the same information, just parsed
a bit differently.

Joe J.

06-23-2002, 11:19 PM
Posted by Joe Ross at 2/6/2001 2:34 AM EST

Engineer on team #330, Beach Bot, from Hope Chapel Academy and NASA/JPL , J&F Machine, and Raytheon.

In Reply to: delta_t and packet_num
Posted by Joe Johnson on 2/5/2001 10:11 PM EST:

eom means end of message