View Full Version : DS1820 resolution
RFsolution
- 13th December 2007, 19:34
Hi
If I understand well it should be possible to lower the resolution of the DS1820
in order to speed-up the conversion time ?
As I want to use several DS1820's and return there value on a HSERIN request
this migh be a possibility
Further I dont need more than 1 or 0.5 deg resolution
Any one succeed in changing the resolution ?
Walter
Darrel Taylor
- 13th December 2007, 20:16
You can change the resolution of the DS18B20, but not the older DS1820.
And yup, it goes much faster.
<br>
RFsolution
- 13th December 2007, 21:21
Sorry Darrel I mean 18B20
Any code example on how to do this ?
Darrel Taylor
- 13th December 2007, 21:31
I do.
Do you feel like beta testing something?
<br>
Darrel Taylor
- 13th December 2007, 23:48
Ok, we'll go the easy way then.
Assuming you're not using the alarms ...
DS18B20_9bit CON %00011111 ; 93.75ms, 0.5°C
DS18B20_10bit CON %00111111 ; 187.5ms, 0.25°C <-- My favorite
DS18B20_11bit CON %01011111 ; 375ms, 0.125°C
DS18B20_12bit CON %01111111 ; 750ms, 0.0625°C (default)
OWOUT DQ, 1, [$CC, $4E, 0, 0, DS18B20_10bit]
HTH,
RFsolution
- 14th December 2007, 11:25
Thanks Darrel
Would it be possible to share your 9/10bit conversion routine to degrees centigrade
? Walter
Darrel Taylor
- 14th December 2007, 13:03
The conversion is the same, no matter which resolution you use.
At lower res, the least signifcant bit's become 0's.
<br>
RichG
- 5th June 2008, 13:52
Using the resolution setting would it be possible to make the 18S20 and the 18B20 interchangeable with the same software? I have tried setting the 18B20 to 9 bit and get readings using my 18S20 programming but get some very high temp readings.
Acetronics2
- 5th June 2008, 14:41
Hi, Rich
The 18S20 and 18B20 readings are just different from a shifting value ...
So just you just have to ask the device for the family code ( 10h for S or 28 h for B ) and shift the result the convenient value ...
That's all.
Alain
Hi, Walter
The SEARCH function for "18B20" will give you the routine ...
Alain
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