ds18s20 reads incorectly

[ecoli-557]

Thanks EarlyBird2, I did figure that part out. In the code that the 'Kid' supplied, I could not get it to work until I remarked the SignC=Negative portion.
The code below works, but I have not tried for negative numbers yet..... Could you explain why?
Thanks and Regards,
Steve

ReadDS18S20:' Works, mostly.....------------------------------------------------
                  owout Tsensor,1,[$CC, $44]                                    'Send Start Temperature Conversion command
                  owout Tsensor,1,[$CC, $BE]                                    'Send Read Temperature command
                  owin Tsensor,0,[STR dq\9]                                     'Retrieve all 9 bytes of data
                  RawTemp.Byte0 = dq[0]
                  RawTemp.byte1 = dq[1]
                  if RawTemp.8 = 1 then                                         'Check if temperature is a negative reading
                     SignC = Negative                                            
                     RawTemp.lowbyte = RawTemp.lowbyte ^ 255                    'Invert data
                  else
                     SignC = Positive
                  endif
                  dummy = RawTemp.0                                             'Store the half degree indicator bit
                  TempC = ((RawTemp.lowbyte) >> 1) * 100                        'Divide raw data by 2 to give real temperature
                  TempC = TempC + (dummy * 50)                                  'Add the half degree is present
'                 if SignC = Negative then                                      'Only proceed if temperature is negative - doesnt work for F, fine for C
'                    if TempC => 1770 then   
'                       SignF = Negative
'                       TempF = (TempC + 5000) * 900
'                       TempF = div32 500
'                       TempF = TempF - 12200
'                    return 
'                  else
'                      SignF = Positive
'                      TempF = (TempC + 5000) * 900
'                      TempF = div32 500
'                      TempF = 12200 - TempF
'                      return 
'                   endif    
'                 endif
                  SignF = Positive                                              'Sign is +
                  TempF = ((TempC * 18) / 10) + 3200                            'Convert from C to F
                  return

[EarlyBird2]

Negative and Positive are declared variables or constants. In your code should be

Negative CON 1
Positive CON 0

Does this help?

Could be SYMBOL or ALIAS of course.

[ecoli-557]

EarlyBird2-
Thanks! I just tried it (I did NOT have them as CONstants), compiles fine but still gives me 0.00F.
Code is below for clarification.
Regards,
Steve

    Positive    con 0                                                           'Bit used for + in the DS18S20
    Negative    con 1                                                           'Bit used for - in the DS18S20
    rawtemp         var word                                                    'Raw temp var
    tempC           var word                                                    'Temp var for degrees C
    tempF           var word                                                    'Temp var for degrees F
    dq              var byte[9]                                                 'String of data from DS18S20
    SignC           var bit                                                     'Bit for + or - for degrees C
    SignF           var bit                                                     'Bit for + or - for degrees F
    dummy           var bit                                                     'Temp var

ReadDS18S20:' Works, mostly.....--Thanks 'Kid' from Forum-----------------------
                  owout Tsensor,1,[$CC, $44]                                    'Send Start Temperature Conversion command
                  owout Tsensor,1,[$CC, $BE]                                    'Send Read Temperature command
                  owin Tsensor,0,[STR dq\9]                                     'Retrieve all 9 bytes of data
                  RawTemp.Byte0 = dq[0]
                  RawTemp.byte1 = dq[1]
                  if RawTemp.8 = 1 then                                         'Check if temperature is a negative reading
                     SignC = Negative                                            
                     RawTemp.lowbyte = RawTemp.lowbyte ^ 255                    'Invert data
                  else
                     SignC = Positive
                  endif
                  dummy = RawTemp.0                                             'Store the half degree indicator bit
                  TempC = ((RawTemp.lowbyte) >> 1) * 100                        'Divide raw data by 2 to give real temperature
                  TempC = TempC + (dummy * 50)                                  'Add the half degree is present
                 if SignC = Negative then                                      'Only proceed if temperature is negative - doesnt work for F, fine for C
                    if TempC => 1770 then   
                       SignF = Negative
                       TempF = (TempC + 5000) * 900
                       TempF = div32 500
                       TempF = TempF - 12200
                    return 
                  else
                      SignF = Positive
                      TempF = (TempC + 5000) * 900
                      TempF = div32 500
                      TempF = 12200 - TempF
                      return 
                   endif    
                 endif
'                  SignF = Positive                                              'Sign is +
'                  TempF = ((TempC * 18) / 10) + 3200                            'Convert from C to F
                  return

This what I have that does work, just not for negatives.....

ReadDS18S20:' Works, mostly.....--Thanks 'Kid' from Forum-----------------------
                  owout Tsensor,1,[$CC, $44]                                    'Send Start Temperature Conversion command
                  owout Tsensor,1,[$CC, $BE]                                    'Send Read Temperature command
                  owin Tsensor,0,[STR dq\9]                                     'Retrieve all 9 bytes of data
                  RawTemp.Byte0 = dq[0]
                  RawTemp.byte1 = dq[1]
                  if RawTemp.8 = 1 then                                         'Check if temperature is a negative reading
                     SignC = Negative                                            
                     RawTemp.lowbyte = RawTemp.lowbyte ^ 255                    'Invert data
                  else
                     SignC = Positive
                  endif
                  dummy = RawTemp.0                                             'Store the half degree indicator bit
                  TempC = ((RawTemp.lowbyte) >> 1) * 100                        'Divide raw data by 2 to give real temperature
                  TempC = TempC + (dummy * 50)                                  'Add the half degree is present
'                 if SignC = Negative then                                      'Only proceed if temperature is negative - doesnt work for F, fine for C
'                    if TempC => 1770 then   
'                       SignF = Negative
'                       TempF = (TempC + 5000) * 900
'                       TempF = div32 500
'                       TempF = TempF - 12200
'                    return 
'                  else
'                      SignF = Positive
'                      TempF = (TempC + 5000) * 900
'                      TempF = div32 500
'                      TempF = 12200 - TempF
'                      return 
'                   endif    
'                 endif
                  SignF = Positive                                              'Sign is +
                  TempF = ((TempC * 18) / 10) + 3200                            'Convert from C to F
                  return

Regards,
Steve

[EarlyBird2]

these two lines are commented out?

' SignF = Positive 'Sign is +
' TempF = ((TempC * 18) / 10) + 3200 'Convert from C to F

so I guess you will get 0 deg F

[ecoli-557]

Steve-
Dunno what I had thought I was looking at, but when I un-commented those other lines, I now get correct readings!
This is now what seems to be working:
BTW, going to be in your neck of the woods this Wednesday, 2 days in London, then take a boat out from South Hampton on a cruise through the Baltics.
Thanks for pushing me in the right track!
Regards,
Steve

ReadDS18S20:' Works, Thanks 'Kid' and Steve from the UK....from Forum-----------
                  owout Tsensor,1,[$CC, $44]                                    'Send Start Temperature Conversion command
                  owout Tsensor,1,[$CC, $BE]                                    'Send Read Temperature command
                  owin Tsensor,0,[STR dq\9]                                     'Retrieve all 9 bytes of data
                  RawTemp.Byte0 = dq[0]
                  RawTemp.byte1 = dq[1]
                  if RawTemp.8 = 1 then                                         'Check if temperature is a negative reading
                     SignC = Negative                                            
                     RawTemp.lowbyte = RawTemp.lowbyte ^ 255                    'Invert data
                  else
                     SignC = Positive
                  endif
                  dummy = RawTemp.0                                             'Store the half degree indicator bit
                  TempC = ((RawTemp.lowbyte) >> 1) * 100                        'Divide raw data by 2 to give real temperature
                  TempC = TempC + (dummy * 50)                                  'Add the half degree is present
                 if SignC = Negative then                                      'Only proceed if temperature is negative - doesnt work for F, fine for C
                    if TempC => 1770 then   
                       SignF = Negative
                       TempF = (TempC + 5000) * 900
                       TempF = div32 500
                       TempF = TempF - 12200
                    return 
                  else
                      SignF = Positive
                      TempF = (TempC + 5000) * 900
                      TempF = div32 500
                      TempF = 12200 - TempF
                      return 
                   endif    
                 endif
                  SignF = Positive                                              'Sign is +
                  TempF = ((TempC * 18) / 10) + 3200                            'Convert from C to F
                  return

[EarlyBird2]

It is Wednesday you are in England the weather is cold, wet and windy. I am so sorry but what do you expect in England on a summers day.

Have a nice cruise to the Baltic.