On Thu, Nov 15, 2007 at 10:11:02AM -0800, Jamey Sharp wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On 11/15/07, mark gross <[EMAIL PROTECTED]> wrote: > > Is there a format specification for the packed 16 byte array of data? I > > would like to check the text dumps. > > You don't trust me? ;-) The text dump I provided contains every bit of > information that has a defined meaning in the binary telemetry, unless > you want the timestamps of all the fragments of the big GPS messages, or > you want stuff from before the last time we turned on the flight > computer. I don't see any way that either of those are useful. It > discards bytes that are uninitialized, but we're trying to do data > analysis here, not fuzzing... > > But here's the format: > > 4-byte big-endian "ID" > 4-byte big-endian timestamp > 8 bytes of data
OK, so now looking at the Rocketview_20050820.log using hexedit which lists out the data in 18 byte chunks. I'm not seeing the above record format, is there some variable length thing going on? > > The ID is a packed bitfield, with only the low 16 bits being > significant. The least significant 4 bits are the "data length", the > next bit is "RTR", and the remaining 11 bits are what CAN calls the > message ID. > > Data length is limited to the range 0..8. If RTR is 1, there is no > actual data, but the length field can still be in the range 0..8. If RTR > is 0, the first "length" bytes of the data have valid data in them. > Does this mean the record length is variable or the valid data in the fixed length record varies? > > Also, the time stamp data in the acceleration is not high enough > > resolution to be unique. > > Nope. We used the value of "jiffies" for each timestamp. We flew a 2.4 > kernel, so HZ was 100. > > You can reasonably assume that the IMU had a good clock, so > reconstructing higher-precision timestamps isn't that hard. You could > similarly reconstruct the timestamps of messages that originated in the > flight computer or on the ground, if desired. > > > ... the perl code git snapshot ... doesn't run to completion > > Hmmm, it Works For Me (tm). It does need to be able to seek on its > input, so don't feed it a pipe. > > > I wrote a python program to average the acc values for the items with > > the same time stamp and make a plot. (see attached) > > Interesting, thanks! > > Jamey > -----BEGIN PGP SIGNATURE----- > Version: GnuPG v1.4.6 (GNU/Linux) > > iD8DBQFHPIutp1aplQ4I9mURAhXoAJ9QD7mdvmjwppRft285TVSLgVlntQCaAzyk > B8cqYXt7eiOOlQSKpmUr+7o= > =+OoI > -----END PGP SIGNATURE-----
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