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vortexe9000
Joined: 07 Jun 2010
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| chfr. |
 Posted: Sat Jan 14, 2012 3:09 am |
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sdf
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Last edited by vortexe9000 on Sun Feb 19, 2012 7:43 am; edited 2 times in total |
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vortexe9000
Joined: 07 Jun 2010
Posts: 50
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| Posted: Sat Jan 14, 2012 10:33 am |
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loop
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Last edited by vortexe9000 on Sun Feb 19, 2012 7:14 am; edited 1 time in total |
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temtronic
Joined: 01 Jul 2010
Posts: 9249
Location: Greensville,Ontario
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| Posted: Sat Jan 14, 2012 11:57 am |
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hmm....I don't see any bias resistors in the RS485 network.....
hmmm... I don't see any caps for any of the xtals of the PICs.... |
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vortexe9000
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| Posted: Sat Jan 14, 2012 1:38 pm |
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jtgation ?
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Last edited by vortexe9000 on Sun Feb 19, 2012 7:15 am; edited 1 time in total |
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temtronic
Joined: 01 Jul 2010
Posts: 9249
Location: Greensville,Ontario
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| Posted: Sat Jan 14, 2012 2:31 pm |
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I think you're saying that the DS18B20 takes too long to read the temperature compared to the MODBUS communications speed.
The hires sampling takes almost 1 second.
If that is so you have a few options....
1) reduce the resolution of the DS18B20. That will reduce the time necessary to get a reading BUT....it won't be as accurate. See the datasheet for more information.
2)Have the slave PIC continuously read the DS18B20 and save in a temporary buffer. When the master asks for the temperature, get the 'buffered' value instead of telling the DS18B20 to read and send.
3) Slow down the MODBUS serial interface( may not be possible ?).
In my datalogging units I use the DS18B20 and sample at a 1Hz rate. |
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vortexe9000
Joined: 07 Jun 2010
Posts: 50
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| Posted: Sat Jan 14, 2012 2:51 pm |
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uijjk
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