I've done some searching on google and within this newsgroup itself to try and answer this question but haven't yet found anything so I figured I'd ask in the hopes it's an easy answer.
I'm using a DS18S20 and a parallel-port-driven relay to model a furnace control system: the DS is taped to a lightbulb the relay turns on and off. The point is to get a decent PID tuning algorithm that can work with a variety of furnace sizes. The problem is that sequential samples of the DS indicate to me that I'm not actually getting updated information, just the same thing I got last time. I read /mnt/1wire/10.(blah)/temperature and get, let's say, 25.75 degrees, call it again two seconds later and get 25.75 degrees, call it another three times and get the same number, then on the sixth call, get 38.2 degrees. It looks to me like the system isn't actually acquiring information from the DS each time. A: is there a way to force new acquisition with each request? B: would +5V external rather than parasitic powered DS help? C: is a two-second cycle time too short? The hardware consists of a homemade diode-based RS232-onewire converter, with a 30 cm long twisted pair going to a single DS18S20, which is parasitically powered. The software is C; I'm using fopen and fscanf to acquire the contents of /mnt/.../temperature and work with the results. I'm not expecting microsecond conversion rates, but it'd be nice if I could get updates every two seconds. Thanks for any help. John ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Owfs-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/owfs-developers
