Temprature conversion --- C to F

[Heckler]

Here is a link to an article that I wrote that describes reading the ONE WIRE DS18b20 temp sensor...


http://www.picbasic.co.uk/forum/cont...r-nine-of-them

[Byte_Butcher]

Thank You Heckler!

That looks like exactly what I need!
I should have known that Darrel had already written something cool to cover it. (Thank You Darrel !!)

I'll have a read through that stuff this evening and report back tomorrow.

[Normnet]

F = C * 9 'DO LESS THE BIT.7 NEG/POS BIT
F = F / 5
IF T_MSB.7 = 1 THEN 'if the sign bit is "1", is minus C
F = 32 - F
else
F = 32 + F
ENDIF

Norm

[Normnet]

F = C * 9 'DO LESS THE BIT.7 NEG/POS BIT
F = F / 5
IF T_MSB.7 = 1 THEN 'if the sign bit is "1", is minus C
F = 32 - F
else
F = 32 + F
ENDIF

Norm

Try again:
F = C * 9 'DO LESS THE NEG/POS BIT
F = F / 5
IF T_MSB.7 = 1 THEN 'if the sign bit is "1", is minus C
F = F - 32
else
F = F + 32
ENDIF

[Heckler]

Hey ByteButcher...
bear in mind that my code does NOT result in an actual SIGNED value of the Temperature deg F. You end up with the correct temperature in the variable "tempF" and the sign of that value in the variable "sign". It is sutable for display on an LCD or something like that. But you will have to know the value of the "sign" if you want to do further calculations on the value.

PS. I posted the wrong INCLUDE statement...
YOU would use ...
INCLUDE "Temp_Convert.pbp"
(I tried to modify Darrels code to simplify it to only include the needed code to convert C to F and eliminate the Kelvin part. I was really tight on code space for my project.)


There is some good informaiton about temperature conversion here (towards the bottom of the page)... http://www.rentron.com/PicBasic/one-wire2.htm

@Normnet... is it really that simple to convert degrees C to degrees F? across the whole range of -55C to +125C ??

[Normnet]

@Normnet... is it really that simple to convert degrees C to degrees F? across the whole range of -55C to +125C ??

I was thinking on the run above but the following is complete.
C value is * 1000 to hold 4 places.

  C VAR LONG
  F VAR LONG
  iSIGN VAR BIT

  GOTO MAIN

  subC_TO_F:
    F = C * 9
    F = F / 5
    IF iSIGN = 1 THEN 'if the sign bit is "1" is minus C
      IF F > 320000 THEN
        F = F - 320000
        SEROUT2 sSEROUT_PIN,cBAUD,[" -",DEC C/10000,".",DEC4 C," C  = -",DEC F/10000,".",DEC4 F," F",13]
      ELSE
        F = 320000 - F
        SEROUT2 sSEROUT_PIN,cBAUD,[" -",DEC C/10000,".",DEC4 C," C  = ",DEC F/10000,".",DEC4 F," F",13]
      ENDIF
    ELSE
      F = F + 320000
      SEROUT2 sSEROUT_PIN,cBAUD,["  ",DEC C/10000,".",DEC4 C," C  = ",DEC F/10000,".",DEC4 F," F",13]
    ENDIF
  RETURN

  MAIN:

  SEROUT2 sSEROUT_PIN,cBAUD,[" ",13]
  SEROUT2 sSEROUT_PIN,cBAUD,["START",13]

  iSIGN = 1 'NEG
  FOR C = 100 TO 0 STEP -1 '-.0100 C TO 0 C
   GOSUB subC_TO_F
  NEXT

  iSIGN = 0 'POS
  FOR C = 0 TO 100 STEP 1 '0 C TO .0100 C
   GOSUB subC_TO_F
  NEXT


  iSIGN = 1
  FOR C = 550000 TO 0 STEP -10000 '-55.0000 C TO 0 C  'DO STEP -1 FOR COMPLETE BUT FOREVER
   GOSUB subC_TO_F
  NEXT

  iSIGN = 0
  FOR C = 0 TO 1250000 STEP 10000 '0 C TO 125.0000 C  'DO STEP 1 FOR COMPLETE BUT FOREVER
   GOSUB subC_TO_F
  NEXT

  STOP

  END

Norm

[Normnet]

Now displays 4 decimals with round up.

Norm

C VAR LONG
  F VAR LONG
  iSIGN VAR BIT

  GOTO MAIN

  subC_TO_F:
    F = C * 10
    F = F * 9
    F = F / 5
    IF iSIGN = 1 THEN 'if the sign bit is "1" is minus C
      IF F > 3200000 THEN
        F = F - 3200000
        F = F + 5
        F = F / 10
        SEROUT2 sSEROUT_PIN,cBAUD,[" -",DEC C/10000,".",DEC4 C," C  = -",DEC F/10000,".",DEC4 F," F",13]
      ELSE
        F = 3200000 - F
        F = F + 5
        F = F / 10
        SEROUT2 sSEROUT_PIN,cBAUD,[" -",DEC C/10000,".",DEC4 C," C  = ",DEC F/10000,".",DEC4 F," F",13]
      ENDIF
    ELSE
      F = F + 3200000
      F = F + 5
      F = F / 10
      SEROUT2 sSEROUT_PIN,cBAUD,["  ",DEC C/10000,".",DEC4 C," C  = ",DEC F/10000,".",DEC4 F," F",13]
    ENDIF
  RETURN

  MAIN:
  SEROUT2 sSEROUT_PIN,cBAUD,[" ",13]
  SEROUT2 sSEROUT_PIN,cBAUD,["START",13]

  iSIGN = 1
  FOR C = 100 TO 0 STEP -1 '-.0100 C TO 0 C
   GOSUB subC_TO_F
  NEXT

  iSIGN = 0
  FOR C = 0 TO 100 STEP 1 '0 C TO .0100 C
   GOSUB subC_TO_F
  NEXT


  iSIGN = 1
  FOR C = 550000 TO 0 STEP -10000 '-55.0000 C TO 0 C  'DO STEP -1 FOR COMPLETE BUT FOREVER
   GOSUB subC_TO_F
  NEXT

  iSIGN = 0
  FOR C = 0 TO 1250000 STEP 10000 '0 C TO 125.0000 C  'DO STEP 1 FOR COMPLETE BUT FOREVER
   GOSUB subC_TO_F
  NEXT

  STOP

  END

[Byte_Butcher]

Well, I got lost in a world of fire wood this week and haven't had a chance to look through all these great suggestions. But THANKS to everyone for the input so far. Hopefully in the next day or 2 I'll get a chance to try again.

Norm, you're killing me with those "Longs".... that's going to be tough to implement with my 16F887!