Each OW device has a unique ROM ID, which enables you to target a specific device. The first thing you need to do is build and run the example program OWSearch.bas. This program not only serves to test your OW bus, but it also displays the ROM IDs for all devices connected to it. For example,

Using the OW_PIN option is therefore the preferred method of assigning the OW bus pin, in terms of both execution speed and less program ROM being used. Unless there is a compelling reason to do so, do try and avoid the use of SetPin()

The above program sample uses a 20MHz clock, but you may have problems when using a slower clock. For example, 4MHz. This is because the OneWire (OW) library uses indirect addressing to access the OW port pin. If you don't know what indirect addressing means, don't worry - but it does cost many more processor clock cycles than if direct addressing was used. Luckily, the DS18B20 module allows you to use direct addressing. An additional benefit is that direct addressing will generate far less code than direct addressing. Here is how it's done...

// device and clock speed...
device = 18F452
clock = 20

// import modules...
#option OW_PIN = PORTC.0
include "DS18B20.bas"
include "convert.bas"
include "usart.bas"

// FAMILY $28 ($1D) ($0000002CDBAE) <- DS18B20
// FAMILY $28 ($3F) ($0000002CD16E) <- DS18B20
const Sensor_A(8) as byte = ($28, $AE, $DB, $2C, $00, $00, $00, $1D)
const Sensor_B(8) as byte = ($28, $6E, $D1, $2C, $00, $00, $00, $3F)

// display a sensor value...
sub DisplaySensor(byrefconst pID() as byte)
   dim TempA as shortint
   dim TempB as word
   RomID = pID
   Convert
   GetTemp(TempA, TempB)
   USART.Write(DecToStr(TempA),".",DecToStr(TempB,2), $BA, "C",13,10)
end sub

// program start...
SetBaudrate(br115200)
while true
   DisplaySensor(Sensor_A)
   DisplaySensor(Sensor_B)
   delayms(1000)
wend

It's virtually identical to the previous code example, except I've removed the call to SetPin() and put

#option OW_PIN = PORTC.0

before the module includes. Notice the emphasis on before. Options should always be declared before you include a module so that the Swordfish pre-processor can calculate a value before it is used in a module.

Using the OW_PIN option is therefore the preferred method of assigning the OW bus pin, in terms of both execution speed and less program ROM being used. Unless there is a compelling reason to do so, try and avoid the use of SetPin()