DS1820 - Help I'm rusty !

[malc-c]

OK, just received some extra goodies for my easyPIC5 board, one of which is a DS1820 temp sensor. I've used Bruce's example as a starting point and edited it to work with the 2 x 16 LCD on the EasyPIC5 board, but I don't get anything displayed on the screen.

Its been a while since I did any programming, so I'm a tad rusty, Can someone give me some direction. Here are the main points:

16F887 running with 20Mhz
DS1820 output set to RA5
LCD on portB as per the user manual

TRISA=%11111111                                                 ' set PORTA as all input 
TRISB=%00000000                                                 ' set PORTB as all output            
DEFINE OSC 20             
DEFINE LCD_DREG PORTB                                           ' LCD data port 
DEFINE LCD_DBIT 0                                               ' LCD data starting bit 0 or 4 
DEFINE LCD_RSREG PORTB                                          ' LCD register select port 
DEFINE LCD_RSBIT 4                                              ' LCD register select bit 
DEFINE LCD_EREG PORTB                                           ' LCD enable port 
DEFINE LCD_EBIT 5                                               ' LCD enable bit 
DEFINE LCD_BITS 4                                               ' LCD bus size 4 or 8 
DEFINE LCD_LINES 2                                              ' Number lines on LCD 
DEFINE LCD_COMMANDUS 2000                                       ' Command delay time in us 
DEFINE LCD_DATAUS 50                                            ' Data delay time in us


Comm_Pin    VAR	PortA.5                                         ' One-wire Data-Pin "DQ" on PortC.0
Busy        VAR BIT                                             ' Busy Status-Bit
TempC       VAR WORD                                            ' Temp in deg C
TempF       VAR WORD                                            ' Temp in deg F
Float       VAR WORD                                            ' Holds remainder for + temp C display
Cold_Bit    VAR  R_Temp.Bit11                                   ' Sign-Bit for +/- Temp. 1 = Below 0 deg C
Real_Cold   CON 1                                               ' Define Real_Cold = 1
Deg         CON 223                                             ' Data to display Deg ° symbol
Sign        VAR BYTE                                            ' +/- sign for temp display
Dummy       VAR BYTE                                            ' Dummy for Div32

Start_Convert:
    OWOUT   Comm_Pin, 1, [$CC, $44]                             ' Skip ROM search & do temp conversion
    
Wait_Up:
    OWIN    Comm_Pin, 4, [Busy]                                 ' Read busy-bit
    IF      Busy = 0 THEN Wait_Up                               ' Still busy..?, Wait_Up..!
    OWOUT   Comm_Pin, 1, [$CC, $BE]                             ' Skip ROM search & read scratchpad memory
    OWIN    Comm_Pin, 2, [R_Temp.Lowbyte, R_Temp.Highbyte]      ' Read two bytes / end comms
    GOSUB   Convert_Temp
    GOTO    Start_Convert
    
Convert_Temp:                                                   ' +32.0 to +257 F 
    IF      Cold_Bit = Real_Cold THEN Yikes                     ' If Cold_Bit = 1, it's below "0" deg C
    Sign  = "+"
    Dummy = 625 * R_Temp                                        ' Multiply to load internal registers with 32-bit value
    TempC = DIV32 10                                            ' Use Div32 value to calculate precise deg C
    Dummy = 1125 * R_Temp
    TempF = DIV32 100
    IF TempF >6795 THEN                                         ' Over 99.5 deg F..?
       TempF = TempF + 3200
       lcdout $FE, 1," TempF = ",Sign,DEC TempF DIG 4,_
       DEC TempF DIG 3,DEC TempF DIG 2,".",DEC2 TempF,Deg,"F "
    ELSE
       TempF = TempF + 3200
       LCDOUT $FE,$C0, " TempF = ",Sign,DEC TempF DIG 3,_
       DEC TempF DIG 2,".",DEC2 TempF,Deg,"F "
    ENDIF
    TempC  = (R_Temp & $0FF0) >> 4                              ' Mask middle 8-bits, shift into lower byte
    Float = ((R_Temp.Lowbyte & $0F) * 625)                      ' Lower 4-bits of result * 625
    RETURN

Yikes:                                                          ' Display full range -C to -F conversion
    Sign   = "-"                                                ' Display - symbol for negative temp
    Dummy  = 625 * ~R_Temp+1                                    ' Multiply to load internal registers with 32-bit value
    TempC  = DIV32 10                                           ' Use Div32 value to calculate precise deg C
    TempF  = ~R_Temp / 16                                       ' Begin conversion from -C to deg +/-F
    IF TempF >=18 THEN                                          ' Check for -degrees F "-18 C = -0.4 F"
       TempF   = ((((TempF + 50) * 9) /5) -122)                 ' -C to -F below -17 deg C
       lcdout $FE, 1," TempF = ",Sign, DEC TempF,Deg,"F     "
       LCDOUT $FE,$C0, " TempC = ",Sign,DEC TempC DIG 4,_
       DEC TempC DIG 3,".",DEC3 TempC,Deg,"C "

    ELSE                                                        ' Else result = +deg F
       TempF   = ((((-TempF + 50) * 9) /5) -58)                 ' -C to +F below 32.0 deg F to -17 deg C
     lcdout $FE, 1, " TempF = ","+",DEC TempF,Deg,"F     "
      LCDOUT $FE,$C0 , " TempC = ",Sign,DEC TempC DIG 4,_
       DEC TempC DIG 3,".",DEC3 TempC,Deg,"C "

    ENDIF
    RETURN
    
    END

There are a few compiling errors,
Cold_Bit VAR R_Temp.Bit11 gives "a bad data type"
OWIN Comm_Pin, 2, [R_Temp.Lowbyte, R_Temp.Highbyte] gives "expected [" and "expected ]" even though the exist
and half a dozen "bad expressions"

The example was for a serial LCD, where as mine is a traditional parallel one in 4 bit mode, so I've tried to convert the example, but its not displaying anything, even though it was cut and pasted from a bit of code I wrote a year ago which worked (just changed portC to port B for the use on the development board)

I'm sure its missing something really obvious. Should I still configure the chip, or use the settings in the Flash2 programmer software.

TIA

[skimask]

Cold_Bit VAR R_Temp.Bit11 gives "a bad data type"

Not seeing where R_Temp is declared!

OWIN Comm_Pin, 2, [R_Temp.Lowbyte, R_Temp.Highbyte] gives "expected [" and "expected ]" even though the exist
and half a dozen "bad expressions"

Are you using PBP 2.50A? There was a bug in the OWIN/OWOUT that was addressed here on the forums awhile back. Might apply to you if using PBP2.50A, not sure if the A patch covered the bug or not.
http://www.picbasic.co.uk/forum/show...ighlight=2.50a

[malc-c]

Thanks for the comments, I said i was rusty

Using a some what older version 2.47

[skimask]

Using a some what older version 2.47

Then it's back to declaring R_Temp

[malc-c]

Ok, with a bit of head scratching I've managed to get the LCD to display some text, and then added an edited section of Bruce's code to get the DEC value of TEMPf displayed on the screen

ANSEL  = 0                             
ANSELH = 0                                                
DEFINE OSC 20            
DEFINE LCD_DREG PORTB
DEFINE LCD_DBIT 0
DEFINE LCD_RSREG PORTB
DEFINE LCD_RSBIT 4
DEFINE LCD_EREG PORTB
DEFINE LCD_EBIT 5
DEFINE LCD_BITS 4
DEFINE LCD_LINES 2
DEFINE LCD_COMMANDUS 1000
DEFINE LCD_DATAUS 100

Comm_Pin    VAR	PortA.5     ' One-wire Data-Pin "DQ" on PortA.5
Busy        VAR BIT         ' Busy Status-Bit
R_Temp      VAR	WORD        ' RAW Temperature readings
TempC       VAR WORD        ' Temp in deg C
TempF       VAR WORD        ' Temp in deg F
Float       VAR WORD        ' Holds remainder for + temp C display
Cold_Bit    VAR R_Temp.Bit11' Sign-Bit for +/- Temp. 1 = Below 0 deg C
Real_Cold   CON 1           ' Define Real_Cold = 1
Sign        VAR BYTE        ' +/- sign for temp display
Dummy       VAR BYTE        ' Dummy for Div32

Start_Convert:
    OWOUT   Comm_Pin, 1, [$CC, $44]                             ' Skip ROM search & do temp conversion
    
Wait_Up:
    OWIN    Comm_Pin, 4, [Busy]                                 ' Read busy-bit
    IF      Busy = 0 THEN Wait_Up                               ' Still busy..?, Wait_Up..!
    OWOUT   Comm_Pin, 1, [$CC, $BE]                             ' Skip ROM search & read scratchpad memory
    OWIN    Comm_Pin, 2, [R_Temp.Lowbyte, R_Temp.Highbyte]      ' Read two bytes / end comms
    GOSUB   Convert_Temp
    GOTO    Start_Convert
    
Convert_Temp:                                                   ' +32.0 to +257 F 

    Sign  = "+"
    Dummy = 625 * R_Temp                                        ' Multiply to load internal registers with 32-bit value
    TempC = DIV32 10                                            ' Use Div32 value to calculate precise deg C
    Dummy = 1125 * R_Temp
    TempF = DIV32 100
    IF TempF >6795 THEN                                         ' Over 99.5 deg F..?
       TempF = TempF + 3200
lcdout $FE,1," Temp F = ",Sign,DEC TempF
    ELSE
       TempF = TempF + 3200
       LCDOUT $FE,1, " Temp F = ",Sign,DEC TempF 
    ENDIF
    TempC  = (R_Temp & $0FF0) >> 4                              ' Mask middle 8-bits, shift into lower byte
    Float = ((R_Temp.Lowbyte & $0F) * 625)                      ' Lower 4-bits of result * 625
    RETURN

The code compiles and loads OK, and I get the value (3199) shown on the screen, but seem to have a few niggles I can't workout what settings I need to change.

1) - if viewed at an angle, the display seems to be scanning (ie its similar to the effect when filming a TV and you get a black bar slowley moving over the picture)

2) - holding the DS1820 between fingers I would expect the value to change, but it doesn't

Any guidance would help

[malc-c]

Cutting and pasting the following from Bruce's example gives a bad expression error at the line beginning DEC TempF DIG 3

lcdout $FE,1," TempF = ",Sign,DEC TempF DIG 4,_
DEC TempF DIG 3,DEC TempF DIG 2,".",DEC2 TempF,Deg,"F "

EDIT:
Resolved (sort of !)

lcdout $FE,1," TempF = ",Sign,DEC TempF DIG 4,DEC TempF DIG 3,DEC TempF DIG 2,".",DEC2 TempF,"F "

Gives TempF = +031.99 on the LCD. Seems it was the "Deg" statement that was causing the issue. More work to do to get it reading the correct temperature (ie drop the 0) and if I recal 32F is 0 C and its not that cold in here !!!

[Acetronics2]

Hi, Malc

... Just try this one !!!

Hits the 10000 characters ... so, no code window !!!


It's been written for EP5 and DS18B20 ( I suppose you have a 18B20 as the 1820 is off production - if real 1820, ... nothing to change !!! )

you just have to add the °C to °F feature ...

I won't do everything for you ... be serious !!! ( LoL )

Alain

[davewanna]

I have not used OW, but I can comment on the LCD Problem.
LCDOUT $FE,1 Clears the LCD Panel. So you are clearing the whole screen, every time it goes through the loop.

Depending on the speed of the loop, this can give issues like flashing display, flickering, or scanning that I have seen.

The way I do it, is a LCDOUT $fe,1 before the loop to clear the LCD... Then, to display the data...

lcdout $FE,$80," Temp F = ",Sign,DEC TempF,"   "
    ELSE
       TempF = TempF + 3200
       LCDOUT $FE,$80, " Temp F = ",Sign,DEC TempF,"   "

Be sure to add some spaces onto the end of the displayed temp (" ") so that when it goes from 10 to 9 degrees... you don't end up with 90. It is messier to code this way, but will result in a 100% flicker-free LCD...

Only use $FE,1 to clear the entire screen when you have to.

[malc-c]

Be sure to add some spaces onto the end of the displayed temp (" ") so that when it goes from 10 to 9 degrees... you don't end up with 90. It is messier to code this way, but will result in a 100% flicker-free LCD...

Only use $FE,1 to clear the entire screen when you have to.

Hey, don't knock it, I'm not a perfectionist, if it gets the desired result then that is all that matters.

[malc-c]

Alain, thanks for the code, I'll have a play later and see what I get

[malc-c]

Alain, I had to make some changes to suit the 16F887 (it didn't like the config bits and turning off comparitors for some reason), but I get the following displayed on screen

-23tC 0.06 -28T

Followed by a scale on second line with a rocket under the - of -28 (if that makes sence)

However I still can't get any change by placing my warmed hands on the DS chip.

Is there any way to test the DS device as it doesn't seem to be doing anythig

[davewanna]

Malc-c..

Not nocking it at all! I had the LCD in my main project working like this for ages. The way I do it now is harder to code, and to change.. Often after a code change I end up with stray characters stuck on the screen after it changes page. Have to put in " "s all over the place to make sure everything is erased. But I got sick of the missus saying "Why is the display flickering like that?" on my home-made climate control in the car.

I should rephrase to...
I only use $FE,1 to clear the entire screen when I have to.

[Acetronics2]

Hi, Malc

If your sensor gives ONE TIME the correct temp ...

it is obvious ... you forgot to close the never-ending measuring Loop ... ( Mr de la Pallice )


....


Did you modify the program ??? ( else than just config bits, Osc speed ... etc )


-23tC 0.06 -28T

This should tell your DS 1820 is in a freezer ...

is it the truth ???

I will do a test ( must solder a dedicated cable ) to see if I can have a delicious ice-cream ...


the first line indicates : Bottom value of scale, actual temp, Top value of scale
second line is scale and index showing where you are between Bottm value and Top value ...

The "rocket" means the heating Output is ON ...

Alain

I give you the test results for negative temp ... keep on the line !

[malc-c]

No, Alain, I'ts not that cold in here

I've done some searching on the net and tried the examples found at http://astrosurf.com/soubie/fichiers/RS_Test_DS1820.pbp and included the routines http://astrosurf.com/soubie/fichiers...0_Routines.pbp

The first thing I did was to leave the pin the DS is connected to as default and after loading the HEX the display did indeed state that the sendor was not detected. I then edited the code to point to pin RA5 as that is what I've set the jumper to on the EasyPIC5 board. I also remmed out all the lines not needed as per his comments, and remmed out the stored value and the gosubs for degrees Kelivin etc, so the display would simply show "Temp is" on line 1 and what the temp reads on line 2

On re-compiling / loading the HEX the display does indeed display a reading, -274.0 C

I've never worked with 1-wire devices, but assume that it gets interigated, sends a value which is stored in the PIC, which is then worked on with the maths to convert it to a temp reading? - I tried an experiment, I turned off the power and removed the DS sensor, and turned on the board, hoping that the display would tem ne no sensor detected. However it still read -274 C. Could it be that the 10K resistor between DQ and the 5v line is causing the PIC to read incorectly ???

Oh and just to confirm I have the DS device installed the right way round

[Acetronics2]

Hi, Malc

LoL ...

as it was a Home thermostat, ... I was not in a hurry to deal with neg temps and had left them aside ...

Corrected now !

( was some fun to correctly display - 0.25 °C ... for info ! )

Alain

PS the DS is in my Deep freezer : - 20 °C .... pretty good !

re PS : Porta.0 and PORTA.1 have to be Hi Weak pulled up ...

[malc-c]

Hi Alain, it's now getting hot in here !

I found another example on the net and pasted that into a new program that included my know LCD working code. The only switch activated on the board is SW9-7 for backlight.

temperature VAR	WORD			' Temperature storage
count_remain VAR BYTE			' Count remaining
count_per_c VAR	BYTE			' Count per degree C

DQ	VAR	PORTA.5			' One-wire data pin


' Define LCD registers and bits
;set PORTB as all output 

ANSEL  = 0                             
ANSELH = 0                                                 
DEFINE OSC 20            
DEFINE LCD_DREG PORTB
DEFINE LCD_DBIT 0
DEFINE LCD_RSREG PORTB
DEFINE LCD_RSBIT 4
DEFINE LCD_EREG PORTB
DEFINE LCD_EBIT 5
DEFINE LCD_BITS 4
DEFINE LCD_LINES 2
DEFINE LCD_COMMANDUS 1000
DEFINE LCD_DATAUS 100

ADCON1 = 7			' Set PORTA and PORTE to digital



mainloop: OWOut DQ, 1, [$CC, $44]       ' Start temperature conversion

waitloop: OWIn DQ, 4, [count_remain]	' Check for still busy converting
	IF count_remain = 0 Then waitloop

	OWOut DQ, 1, [$CC, $BE]		' Read the temperature
        OWIn DQ, 0, [temperature.LOWBYTE, temperature.HIGHBYTE, Skip 4, count_remain, count_per_c]

	' Calculate temperature in degrees C to 2 decimal places (not valid for negative temperature)
	temperature = (((temperature >> 1) * 100) - 25) + (((count_per_c - count_remain) * 100) / count_per_c)
	LCDOut $fe, 1, DEC (temperature / 100), ".", DEC2 temperature, " C"

	' Calculate temperature in degrees F to 2 decimal places (not valid for negative temperature)
	temperature = (temperature */ 461) + 3200
	LCDOut $fe, $c0, DEC (temperature / 100), ".", DEC2 temperature, " F"

        Pause 1000                      ' Display about once a second

	GoTo mainloop			' Do it forever

The display now reads:
654.11 C
554.54 F

I'm just wondering if the DS device is faulty ?

I'll give your revised code a try later - I need a break !

[malc-c]

Ok, I found the example on the EasyPIC5 CD (I know it should of been the first place to look, but as it was called one-wire and not temp sensor you can understand why I missed it - I said I was rusty !)

This works and gives a real temp of 25 degree C which rises when I touch the sensor. I apologise now as the following is not PBP - but hopefully someone can tell me why I was having so much trouble with PBP

' *
' * Project name
'     Onewire_Test (Interfacing the DS18x20 temperature sensor - all versions)
' * Copyright
'     (c) MikroElektronika, 2005-2008
' * Description
'     After reset, PIC reads temperature from the sensor and prints it on the Lcd.
'     The display format of the temperature is 'xxx.xxxx°C'. To obtain correct
'     results, the 18x20's temperature resolution has to be adjusted (constant
'     TEMP_RESOLUTION)
' * Test configuration
'     MCU             PIC16F887
'     Dev.Board       EasyPIC5
'     Oscillator      HS, 08.0000 MHz
'     Ext. Modules    DS18x20 connected to RE2 pin, LCD_2x16
'     SW              mikroC v8.0
' * NOTES
'     - Pull up and turning off diode on pin used for one wire bus may be required.
' *

program Onewire_Test

'  Set TEMP_RESOLUTION to the corresponding resolution of used DS18x20 sensor
'  18S20 9  (default setting can be 9,10,11,or 12)
'  18B20 12
const TEMP_RESOLUTION as byte = 9
dim  text as string[8]
     temp as word

sub procedure Display_Temperature(dim temp2write as Word)
const RES_SHIFT as byte = TEMP_RESOLUTION - 8
dim temp_whole as byte
    temp_fraction as Word

  text = "000.0000"

  ' check if temperature is negative
  if (temp2write and $8000) = 0x8000 then

     text[0] = "-"
     temp2write = not temp2write + 1
  end if

  ' extract temp_whole     0
  temp_whole = temp2write >> RES_SHIFT

  ' convert temp_whole to characters
  if (temp_whole/100) then
     text[0] = temp_whole/100  + 48
  end if
  text[1] = (temp_whole/10) mod 10 + 48             ' extract tens digit
  text[2] =  temp_whole mod 10     + 48             ' extract ones digit

  ' extract temp_fraction and convert it to unsigned int
  temp_fraction  = temp2write << (4-RES_SHIFT)
  temp_fraction  = temp_fraction and $000F
  temp_fraction = temp_fraction * 625

  ' convert temp_fraction to characters
  text[4] =  temp_fraction/1000    + 48         ' extract thousands digit
  text[5] = (temp_fraction/100) mod 10 + 48         ' extract hundreds digit
  text[6] = (temp_fraction/10) mod 10  + 48         ' extract tens digit
  text[7] =  temp_fraction mod 10      + 48         ' extract ones digit

  ' print temperature on LCD
  Lcd_Out(2, 5, text)
end sub'~

main:
  ANSEL  = 0                              ' Configure AN pins as digital I/O
	ANSELH = 0
  Lcd_Config(PORTB,3,2,1,0,PORTB,4,7,5) ' Lcd_Init_EP5, see Autocomplete
  Lcd_Cmd(LCD_CURSOR_OFF)
  Lcd_Out(1, 1, " Temperature   ")
  ' Print degree character, 'C' for Centigrades
  Lcd_Chr(2,13,223)
  Lcd_Chr(2,14,"C")

  '--- main loop
  while TRUE
    '--- perform temperature reading
    Ow_Reset(PORTE,2)            ' Onewire reset signal
    Ow_Write(PORTE,2,$CC)       ' Issue command SKIP_ROM
    Ow_Write(PORTE,2,$44)       ' Issue command CONVERT_T
    Delay_us(120)

    Ow_Reset(PORTE,2)
    Ow_Write(PORTE,2,$CC)       ' Issue command SKIP_ROM
    Ow_Write(PORTE,2,$BE)       ' Issue command READ_SCRATCHPAD

    temp =  Ow_Read(PORTE,2)
    temp = (Ow_Read(PORTE,2) << 8) + temp

    '--- Format and display result on Lcd
    Display_Temperature(temp)

    Delay_ms(500)
  wend
end.

Maybe its time to learn a new language

[CocaColaKid]

Just some food for thought. This is the code I use for reading the DS18S20.

ReadDS18S20:
    owout sensor,1,[$CC, $44]                       ' Send Start Temperature Conversion command
    owout sensor,1,[$CC, $BE]                       ' Send Read Temperature command
    owin sensor,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
        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
    TempF = TempC * 18 / 10 + 3200
    return

This is the code I use for the DS18B20. This one also includes the CRC calculation.

ReadDS18B20:
    low portb.7 : low portb.6 : low portb.5
    pause 10
    owout sensor,1,[$CC,$44]
    low RailPullUp
    pause 750
    high RailPullUp
    owout sensor,1,[$CC,$BE]
    owin sensor,0,[STR dq\9]
    rawtemp.Byte0 = dq[0]
    rawtemp.Byte1 = dq[1]
    gosub getcrc
    if SensorError[sensor] = 1 and y < 3 then ReadDS18B20
    gosub ConvertTemp
    if SensorError[sensor] = 1 then
        y = 0
        TempC = 0
        TempF = 3200
        Signc = Positive
        SignF = Positive
    endif
    high portb.7 : high portb.6 : high portb.5
    return
    
ConvertTemp:
    if NegBit = 1 then BelowZero
    SignC = Positive
    SignF = Positive
    dummy = 625 * RawTemp
    TempC = DIV32 100
    dummy = 0
    dummy = 1125 * Rawtemp
    TempF = DIV32 100
    TempF = TempF + 3200
    return

BelowZero:
    SignC = Negative
    dummy = 0
    RawTemp.byte0 = RawTemp.byte0 ^ 255
    RawTemp.Byte1 = RawTemp.byte1 ^ 255
    dummy = 625 * RawTemp + 1
   	TempC = DIV32 100
    TempF = (TempC + 5000) * 900
    TempF = DIV32 500
    if RawTemp >= 285 then
        TempF = TempF - 12199
        SignF = Negative
        else				
        TempF = 12199 - TempF
        SignF = Positive
	endif
	return

'------------------------ Calculate the CRC from Byte 9 ------------------------

GetCRC:
    for x = 0 to 7
    DataByte = dq[x]
    gosub CalcCRC
    next x
    if dq[8] <> CRCCalc then
        SensorError[sensor] = 1
        y = y + 1
        else
        SensorError[sensor] = 0
        y = 0
    endif
    CRCCalc = 0                
    return

'--------------------- CRC Bit Calcuation Method -------------------------------

CalcCRC:
    for i = 0 to 7
    DataBit = CRCCalc.0 ^ DataByte.0
    DataByte = DataByte >> 1
    if DataBit = 0 then Shift
    CRCCalc = CRCCalc ^ $18

Shift:
    CRCCalc = CRCCalc >> 1
    CRCCalc.7 = DataBit
    next i
    return

[Copy'nPaste]

"Maybe its time to learn a new language "

He he, don't let Alain hear you say that :-)
Pbp is somewhat dated, mE basic example is for the new DS 18S20, note the "S".
It has slightly reduced resolution from the DS 1820, or DS18B20 as it's now known, therefore the code to interrogate the device, and change the data into "English" :-) is different.
No, I don't have the solution, but at least I have a clear understanding of the problem, I think.

[CocaColaKid]

The DS1820 and the DS18S20 were software interchangeable as we started out using the 1820 and then switched to the 18S20 when we could not get the other. We changed nothing I our code from my memory though.

[malc-c]

"Maybe its time to learn a new language "

He he, don't let Alain hear you say that :-)

LOL - only kidding, it's taking me all these years to get my head pbp and I'm still getting it wrong - Alain, I'm not going nowhere

@coke

Many thanks for posting your code - I'll give it a try now that I know the hardware is sound.