Returning whole numbers for DS1820?

Hello,

I'm using an example code for a DS1820 that does the math for the display to show either Fahrenheit or Celsius to 2 decimal places. I don't understand the math that's done here and was wondering if anyone could suggest a way to do the conversion without the decimal places.

This works fine and isn't a problem in my programs but I'd like to use Darrel Taylor's "Temp_Convert" include file so I can display negative temperatures and I think the math here is screwing up the conversion in the include file. In his example code "Test_Temp_Convert" the temperatures are declared before the conversion with whole numbers so I thought if I could get whole numbers returned with the code I'm using below then the include file might work. Has anyone used Darrels "Temp_Convert" include file with a DS1820? I'd be grateful for any help.

Thanks
jessey

Code:

Update_Pond_Temperature: OWOut Sensor_Input, 1, [$CC, $44] ' Start Water_Temp conversion waitloop: OWIn Sensor_Input, 4, [count_remain] ' Check for still busy converting IF count_remain = 0 THEN waitloop OWOut Sensor_Input, 1, [$CC, $BE] ' Read the Water_Temp OWIn Sensor_Input, 0, [Water_Temp.LOWBYTE, Water_Temp.HIGHBYTE, _ Skip 4, count_remain, count_per_c] IF Temp_Displayed = Celsius then ' Calculate Water_Temp in degrees C to 2 decimal places Water_Temp = (((Water_Temp >> 1) * 100) - 25) _ + (((count_per_c - count_remain) * 100) / count_per_c) RETURN ENDIF IF Temp_Displayed = Fahrenheit then ' Calculate Water_Temp in degrees C to 2 decimal places Water_Temp = (((Water_Temp >> 1) * 100) - 25) _ + (((count_per_c - count_remain) * 100) / count_per_c) ' Convert Water_Temp from Celsius degrees to Fahrenheit to 2 decimal places Water_Temp = (Water_Temp */ 461) + 3200 RETURN ENDIF

Then to display I use this:

Code:

IF Temp_Displayed = Fahrenheit then LCDOut $fe, $c0,"H2o=",DEC Water_Temp / 100,0,"F " ENDIF IF Temp_Displayed = Celsius then LCDOut $fe, $c0,"H2o=",DEC Water_Temp / 100,0,"C " ENDIF

If I understand your question correctly, I think all you need to do is to shift right (not rotate right) the intial temperature result.

On the DS18S20, each count of the 9-bit result is one-half degree Celsius. In other words the least significant bit is the half-degree "count". After shifting right once, this bit is "tossed" and the least significant bit will hold the whole-degree "count".

Thereafter, you can process the result as an 8-bit whole number.

Hi Jessey,

Try this...
http://www.picbasic.co.uk/forum/showthread.php?p=20470

Should work with both Positive and Negative temperatures.
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Thanks Darrel

Hi Darrel,

Are you suggesting that your code snip will work without using your "Temp_Convert" include file with my DS1820? I've tried it every which way with & without the include file and I can't seem to get it to work. Is there a sample on the list here that shows how its set up using a DS1820?

Code:

Print_To_2nd_Line_Of_Lcd:' ,".",DEC2 Water_Temp, Sign = TempC.15 TempC = ABS(TempC) TempC =(TempC>>1)*10 + (TempC.0 * 5) IF Sign then IF Its = Dark THEN IF Temp_Displayed = Fahrenheit then LCDOut $fe, $c0,1,"H2o = -",DEC Water_Temp / 10,".",DEC2 Water_Temp,0,"F" ENDIF IF Temp_Displayed = Celsius then LCDOut $fe, $c0,1,"H2o = -",DEC Water_Temp / 10,".",DEC2 Water_Temp,0,"C" ENDIF ELSE'if its light then show the print below IF Temp_Displayed = Fahrenheit then LCDOut $fe, $c0,2,"H2o = -",DEC Water_Temp / 10,".",DEC2 Water_Temp,0,"F" ENDIF IF Temp_Displayed = Celsius then LCDOut $fe, $c0,2,"H2o = -",DEC Water_Temp / 10,".",DEC2 Water_Temp,0,"C" ENDIF ENDIF ELSE IF Its = Dark THEN IF Temp_Displayed = Fahrenheit then LCDOut $fe, $c0,1,"H2o=",DEC Water_Temp / 100,".",DEC2 Water_Temp,0, _ "F ",DEC Lite_Level ENDIF IF Temp_Displayed = Celsius then LCDOut $fe, $c0,1,"H2o=",DEC Water_Temp / 100,".",DEC2 Water_Temp,0, _ "C ",DEC Lite_Level ENDIF ELSE'if its light then show the print below IF Temp_Displayed = Fahrenheit then LCDOut $fe, $c0,2,"H2o=",DEC Water_Temp / 100,".",DEC2 Water_Temp,0, _ "F ",DEC Lite_Level ENDIF IF Temp_Displayed = Celsius then LCDOut $fe, $c0,2,"H2o=",DEC Water_Temp / 100,".",DEC2 Water_Temp,0, _ "C ",DEC Lite_Level ENDIF ENDIF ENDIF RETURN

This is how I read the temperature:

Code:

Update_Pond_Temperature: OWOut Sensor_Input, 1, [$CC, $44] ' Start Water_Temp conversion waitloop: OWIn Sensor_Input, 4, [count_remain] ' Check for still busy converting IF count_remain = 0 THEN waitloop OWOut Sensor_Input, 1, [$CC, $BE] ' Read the Water_Temp OWIn Sensor_Input, 0, [Water_Temp.LOWBYTE, Water_Temp.HIGHBYTE, _ Skip 4, count_remain, count_per_c] ' Calculate Water_Temp in degrees C to 2 decimal places Water_Temp = (((Water_Temp >> 1) * 100) - 25) _ + (((count_per_c - count_remain) * 100) / count_per_c) IF Temp_Displayed = Celsius then RETURN 'IF the Temp_Displayed = Fahrenheit then Convert C to F before returning Water_Temp = (Water_Temp */ 461) + 3200 RETURN

When the temperature drops below 32 degrees F then it displays 556 instead of 31. I'd surely appreciate any further help you could provide.

Thanks
jessey

Oops, I should have looked closer. Didn't see you're using the extended resolution. That routine was for .5 deg resolution.

OK, so when the temp drops below 32°F, it means that the °C is going negative. And negative values can't be multiplied or divided in PBP. So the "extended Resolution" formula gives the wrong answer.

Same problem with the Fahrenheit conversion, And the LCDOUT statements.

Here's what I think should work...(untested)

After reading the DS1820, change the second half of Update_Pond_Temperature: to this...

Code:

' Calculate Water_Temp in degrees C to 2 decimal places Sign = Water_Temp.15 Water_Temp = ((ABS(Water_Temp) >> 1) * 100) if Sign then Water_Temp = -Water_Temp Water_Temp = Water_Temp - 25 _ + (((count_per_c - count_remain) * 100) / count_per_c) IF Temp_Displayed = Celsius then RETURN 'IF the Temp_Displayed = Fahrenheit then Convert C to F before returning Sign = Water_Temp.15 Water_Temp = (ABS(Water_Temp) */ 461) if Sign then Water_Temp = -Water_Temp Water_Temp = Water_Temp + 3200 RETURN

Then change the lcd routine to this...

Code:

Print_To_2nd_Line_Of_Lcd: LCDOut $fe, $c0 IF Its = Dark THEN LCDOUT 1 else LCDOUT 2 endif LCDOut "H2o = " if Water_Temp.15 then LCDOut "-" Water_Temp = ABS(Water_Temp) LCDOut DEC Water_Temp / 100,".",DEC2 Water_Temp,0 IF Temp_Displayed = Fahrenheit then LCDOut "F " else lcdout "C " endif IF Its <> Dark THEN lcdout DEC Lite_Level endif RETURN

You don't need the Temp_Convert include file.

HTH,

Thanks Darrel

Hi Darrel,

Looks like I owe you some more beer, your code works excellent. My Pond Pump Controller circuit works great now. Really appreciated.

Thanks
jessey

Woohoo! It's like Beer in the bank.

Now I just need to find a local Branch office so I can make a withdrawl. :)

__________________
DT

P.S. That's gotta be one COLD pond in B.C. in February.
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