Help with DS18B20 program

[Bruce]

If it's reading all 1's my guess would be it's a bad sensor or you have it wired backwards.
I have wired a few of these backwards, and they refused to work afterwards. Even after
I re-wired it.

With the flat side facing you, pins downward, from left-to-right, are ground, DQ, Vdd.

[presario1425]

With the flat side facing you, pins downward, from left-to-right, are ground, DQ, Vdd.

Just like the way I have it connected.

Really don't remember ever connecting it the wrong way. Then again, I was too excited at the beginning So, I'm guessing either I messed it up at some point, or DigiKey sent me a bad sensor. Wish there was a way to check the sensor (like resistance values across pins etc.) and also wish that these sensors were not $5 a pop. You know any place where they sell these for less than $5?

I can live with a bad sensor knowing that my program had the potential to work Will try again. Anyway, thanks a lot Bruce for all your help.

[KVLV]

you might find the ds18b20 at http://canada.newark.com/

Just like the way I have it connected.

Really don't remember ever connecting it the wrong way. Then again, I was too excited at the beginning So, I'm guessing either I messed it up at some point, or DigiKey sent me a bad sensor. Wish there was a way to check the sensor (like resistance values across pins etc.) and also wish that these sensors were not $5 a pop. You know any place where they sell these for less than $5?

I can live with a bad sensor knowing that my program had the potential to work Will try again. Anyway, thanks a lot Bruce for all your help.

[KVLV]

the thing is you have not mention how fast you are running your PIC. I found that problem when I ran my pic18f4550 with 20HMz, all I read back from the ds18b20 are zero/not connected. If I lower the chip to 4HMz then I can read the temperature.

I don't know how to confirm this, the OWOUT and the OWIN command might be too fast for the ds18b20 to catch up with faster pic chip ?

[Bruce]

Check http://www.findchips.com This shows 6 distributors that stock the 18B20.
Where are you located? I'll send you a used one (at least we know it's working)
if you spring for the postage.

But, before I wrote it off as bad, I would check with what KVLV just said. You might
try using a different I/O-pin, different oscillator speed, etc.

Try a timing test with say an LED on a port pin. Toggle it on & off. Does it toggle at the
speed you expect? If not, it could be a timing issue, and that would definitely be a problem
with 1-wire comms.

LCDOUT can sometimes work just fine. Even if you have the wrong oscillator speed declared.
So I would run a series of tests before I wrote the sensor off as bad. Just in case.