Temperaturüberwachung mit Dallas DS1820

Interface RS232 ⇔ DS1820 (bis zu 127 Stück)

/*
  ds1820mes.c                        Strobl 1999-08-02 / 2002-06-09
  
  (C) Copyright 1999, 2002 by Wolfgang Strobl, all rights reserved
  Free for noncommercial use. mailto:ws@mystrobl.de

  Version for 12c672 processor, English docs
  
Purpose

    Read and decode Dallas DS1820 temperature sensors wired through
    a "1-wire" (tm) bus, optionally drive a single fan, 9600 Baud serial
    interface for input and output.
    
Features

  * Command driven, command input via RS232, data output via RS232
    messages

  * Enumerates up to 127 Dallas DS1820 "1-wire" temperature sensors wired
    to a single pin (pin_4 / GP4)
     
  * Read serial no, read scratchpad, get temperature, output result
    in degrees Celsius. 
     
  * Check CRC for serial no and scratchpad
  
  * "parasite power" is supported in this version, only two wires needed
  
  * Use one of the DS1820 on the bus for storing the time between two
    measurements (because the 12c672 has no EEPROM).

  * Pure C, no external or inline assembly required
  
  * 4MHz operation, exact calibration necessary for software RS232 

How to wire:
  
  All DS1820 in parallel: ground, Pin A4, ground. Up to 127 
  4,7k Pullup on Pin-A4.

  RS232out  via GP2 (protected by a 10k resistor)
  RS232in   via GP5 (protected by a 10k resistor)
  DS1820    via GP4 (4,7k Pullup)
  FAN       via GP1 (use a switch transistor as you see fit)
  
Links:

  DS1820 http://www.dalsemi.com
  12C672 http://www.microchip.com

Beispieloutput:

DS1820-8 2.43 (C) strobl@unser.net 99-08-2
. for menu
# 1. 10 c0 71 26 00 00 00 bd  22.5 C 2230
# 2. 10 1b 70 26 00 00 00 4c  22.0 C 2189
# 3. 10 47 a8 26 00 00 00 7f  22.5 C 2252
(
# 1. 10 c0 71 26 00 00 00 bd  22.5 C 2231
# 2. 10 1b 70 26 00 00 00 4c  22.0 C 2189
# 3. 10 47 a8 26 00 00 00 7f  22.5 C 2253
)
v, d1..d9, ?, f, F, b<x>, m, c to continue>.
d
2

D 10 s.
...written

>m
# 1. 10 c0 71 26 00 00 00 bd  22.5 C 2230
# 2. 10 1b 70 26 00 00 00 4c  22.0 C 2182
# 3. 10 47 a8 26 00 00 00 7f  22.5 C 2255

>F

>b
01 
>?
SP: 2d 00 32 32 ff ff 11 57 19 

>c
(
# 1. 10 c0 71 26 00 00 00 bd  22.5 C 2231
# 2. 10 1b 70 26 00 00 00 4c  21.5 C 2173
# 3. 10 47 a8 26 00 00 00 7f  22.5 C 2257
)
(
# 1. 10 c0 71 26 00 00 00 bd  22.5 C 2230
# 2. 10 1b 70 26 00 00 00 4c  21.5 C 2173
# 3. 10 47 a8 26 00 00 00 7f  22.5 C 2258
)
(
# 1. 10 c0 71 26 00 00 00 bd  22.5 C 2231
# 2. 10 1b 70 26 00 00 00 4c  21.5 C 2171
# 3. 10 47 a8 26 00 00 00 7f  22.5 C 2258
)

Im obigen Beispiel sind z.B. nur drei Sensoren angeschlossen, maximal möglich sind (aufgrund der Konstruktion des Programms) 127 verschiedene Sensoren.

Beispielauswertung

 Olivetti M10 als Steuer- und Anzeigeeinheit

Ein Trivialprogramm liest einen Sensor kontinuierlich aus und stellt die Messwerte wie ein Kurvenschreiber dar.