Marco,  It is the DS18S20, with 3 leads.

For some reason the examples in the book used 2 ports:  Porta 4 to pull =
down the line, and Portb x to read the line.  I didn't know about A4 =
being special open drain at the time, so I switched the code to B0 & B1, =
and it still worked perfectly!  Which was why I asked if another pin =
could be substituted for A4.

Is this normal?

Lindy

-----Original Message-----
From: pic microcontroller discussion list =
[mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of marco.genovesi@libero.it
Sent: Friday, June 04, 2004 12:20
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [PIC:] How to make pin RA4 on 16F877 I/O?

>> ...and I was curious why it took 2 I/O pins to do the communication.  =
I thought 1-wire meant only one.  (-:


Lindy, what Dallas sensor do you have?
a DS1820 - DS18S20.. use only 1 pin for communication (plus ground and =
V+).
Note that there are also other Dallas temperature sensors with different =
protocols, as 2 wire (DS1721) and 3 wire (1620)...


You can find an example of 1 wire protocol on TLOGGER.zip (16F84 & =
DS1820) at:

http://www.nexuscomputing.com/picarchive/files.html

There are other examples on the web, I remember.



Marco









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