From: Linus Torvalds Date: Mon, 18 Jun 2012 23:52:41 +0000 (-0700) Subject: Add some more cochran data parsing code/comments X-Git-Url: http://git.tdb.fi/?a=commitdiff_plain;h=8add7917ce9da2faa7751798c3fb15a24715ae1e;p=ext%2Fsubsurface.git 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 --- diff --git a/cochran.c b/cochran.c index 360f2eb..366e5ea 100644 --- a/cochran.c +++ b/cochran.c @@ -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); }