HW Group HWg-PWR 12, Руководство пользователя

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HWg-PWR 3 / 12 / 25 MANUAL HW group
September 2013 page 40
Datalog format of devices HWg-PWR and HWg-Ares
The data is stored in a simple binary format:
<record1>< record2>< record3><record4><record5>…<recordN>
The record format is following:
- Sensor ID (2 bytes)
- TimeStamp (4 bytes)
- Value (4 bytes)
The TimeTamp is stored in Unix time format
(time_t). More information about the format
you can find for example here
http://en.wikipedia.org/wiki/Unix_time . The
Value is stored without decimal point. An
exponent tells you were you have to move
decimal point to get real value (mathematical
expression: right_value = value * 10
EXP
). On screen shot you can see an example of sensor
with ID = 1012 and exponent -3.
The exponent you can get from values.xml too. On following screen
shot there is the same information about the the same sensor you
can see in values.xml file.
But there is a few little differencies betwen these devices. Some of
them store data in little endian format and others in big endian. More
information about endianness you can see for example here
http://en.wikipedia.org/wiki/Endianness . And some of them store
timestamp in local and others in universal time.
Endiannees TimeStamp
HWg-PWR big devices’s local time
HWg-PWR 25 little devices’s local time
HWg-Ares little universal time (UTC)
/* hwg_pwr_datalog.c
*
* Default is datalog written on standard output.
* Command "hwg_pwr_datalog.exe > out.txt" writes the records into file.
*/
#include <stdio.h>
#include <time.h>
#include <winsock.h>
/* For device HWg-PWR 25 and HWg-Ares uncomment next line */
/* #define ARES */
#ifdef ARES
#define _HTONS_(VAL) ( VAL )
#define _HTONL_(VAL) ( VAL )
#else
#define _HTONS_(VAL) ( htons(VAL) )
#define _HTONL_(VAL) ( htonl(VAL) )
#endif