DS1820 - Help I'm rusty !

[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 !