Add some more cochran data parsing code/comments

The code is pretty useless, the comments perhaps equally so.  I'm trying
to figure out what the data pattern is for the cochran CAN files.  There
definitely *is* a pattern, but it actually seems to be different for the
files of different people - and it's not obvious in any case.

There probably are multiple versions of the format, and there might be
things like "David has a high-pressure sensor, and Alex does not" going
on too.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Linus Torvalds 2012-06-18 16:52:41 -07:00
parent 9c7aaed02a
commit 8add7917ce

View file

@ -150,6 +150,64 @@ static void parse_cochran_header(const char *filename,
free(buf);
}
/*
* Cochran export files show that depths seem to be in
* tenth of feet.
*
* Temperature seems to be exported in Fahrenheit.
*
* Cylinder pressure seems to be in multiples of 4 psi.
*
* The data seems to be some byte-stream where the pattern
* appears to be that the two high bits indicate type of
* data.
*
* For '00', the low six bits seem to be positive
* values with a distribution towards zero, probably depth
* deltas. '0 0' exists, but is very rare ("surface"?). 63
* exists, but is rare.
*
* For '01', the low six bits seem to be a signed binary value,
* with the most common being 0, and 1 and -1 (63) being the
* next most common values.
*
* NOTE! Don's CAN data is different. It shows the reverse pattern
* for 00 and 01 above: 00 looks like signed data, with 01 looking
* like unsigned data.
*
* For '10', there seems to be another positive value distribution,
* but unlike '00' the value 0 is common, and I see examples of 63
* too ("overflow"?) and a spike at '7'.
*
* Again, Don's data is different.
*
* The values for '11' seem to be some exception case. Possibly
* overflow handling, possibly warning events. It doesn't have
* any clear distribution: values 0, 1, 16, 33, 35, 48, 51, 55
* and 63 are common.
*
* For David and Don's data, '01' is the most common, with '00'
* and '10' not uncommon. '11' is two orders of magnitude less
* common.
*
* For Alex, '00' is the most common, with 01 about a third as
* common, and 02 a third of that. 11 is least common.
*
* There clearly are variations in the format here. And Alex has
* a different data offset than Don/David too (see the #ifdef DON).
* Christ. Maybe I've misread the patterns entirely.
*/
static void cochran_profile_write(const unsigned char *buf, int size)
{
int i;
for (i = 0; i < size; i++) {
unsigned char c = buf[i];
printf("%d %d\n",
c >> 6, c & 0x3f);
}
}
static void parse_cochran_dive(const char *filename, int dive,
const unsigned char *decode, unsigned mod,
const unsigned char *in, unsigned size)
@ -187,6 +245,7 @@ static void parse_cochran_dive(const char *filename, int dive,
printf("\n%s, dive %d\n\n", filename, dive);
cochran_debug_write(filename, buf, size);
cochran_profile_write(buf + offset, size - offset);
free(buf);
}