DS1820 - Help I'm rusty !

[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.