ds18s20 reads incorectly

[Acetronics2]

Hi, Cleaver

I suppose you work on an easyPic 4 or 5 ...

try this with sensor connected to PORTE2 and Pullup on porta.0 and 1.

After power on, type of sensor and ID is displayed.

press RA0 Button ( active low ! ) and you turn to thermo mode ( thermostat, in fact , see RA0 and RA.1 use ... )

Alain

PS : Fully PbP Written Program...

[manwolf]

jcleaver

Here is a couple of files for you to play with.

pbptc.txt is your program that correctly displays the temp C and changes when the temp changes. You will need to change the LCD port, I use an easypic5 and you are using a different port.

I also have a program for MikroB attached, again it is for the ep5 board.

Take a few minutes and look at how the temp is being read in both. Once you figure that out you will see where the problem is.

BTW the formula is from the DS18S20 datasheet.





In your Mikro file did you notice that the temp was calculated before it is converted?

if j2 = $FF then
tmp_sign = "-" ' temperature sign
j1= j1 or $FF ' complement of two
j1= j1 + $01
else
tmp_sign = "+"
end if
j2 = (j1 and $01) * 5 ' Get decimal value
j1 = j1 >> 1 ' Get temp value
j1 = ((j1*9/5)+32) 'Convert C to F

And in your PBP file nothing is calculated until after the conversion.

TEMP = ((TEMP*9/5)+32 )
Lcdout $fe, 1, dec (temp >> 1),".",dec(temp.0 * 5)," degrees C"

Good Luck!

Acetronics: May I play around with the thermostat program you posted?

[jcleaver]

Want To Thank All Of You For Your Help Been Great To Work With
Will Keep You Updated

Also Would Like To Look At The Pb Code For The Thermostat Program

If Not Giving Away Something

Again Thanks

Jack

[jcleaver]

Manwolf
Worked With Your Pbp And Your Right It Is Displaying The Correct C Temperature

Its Pb Math Thats Incorect

Any Ideas How ?

Also The Formula Temp = ((temp*1.8)+32) Gives Corect Answer But Wont Compile
On Pbp

[manwolf]

Jack

As Acetronics stated:

Remember PBP works with UNSIGNED INTEGERS ...

So 9/5 = 1.8 still won't fly in PBP

How about something like this?

temp = (((temp >> 1) * 100) - 25) 'calculate degrees C

temp = (temp */ 461) + 3200 'convert degrees C to F

And before you ask, crack open the ugly green book and figure out what '*/' does.

Hint: it uses all unsigned integers.

The hardest part of writing any program is learning how to handle the math. If you can not get your head around the math none of this stuff makes any sense.

Don't be afraid to throw some output in there to see what is happening. Run Debug, output to LCD or a serial port to see what it is changing.


For a better explaination of the math go here - http://www.rentron.com/PicBasic/one-wire3.htm

Ted

[Acetronics2]

Hi, Manwolf

What do you mean by that :

" Acetronics: May I play around with the thermostat program you posted? "

Of course YOU can play with it ...

Alain

[Bruce]

Your bit-banged read & write routines use a @ NOP for a 1uS delay, but you're running
at 20MHz so these are only 200nS. You would need 5 x @ NOP for a 1uS delay.