' Written by Denis Bernard
 ' bernard@xs4all.nl

 ' 1 wire communication with Dallas temperature sensor DS1821
 ' small PR35 Package, 3 pin , ± 2$. See Conrad elec.(europe)
 ' Temperatures are printed in degres when >-1° , <125°
 ' for temperature <0 , 256 - Temp_buf will give from -55 to -1

 $crystal = 24000000 : $baud = 2400
 Config 1wire = P3.3 'use P3.3 for 1 wire communication
 Enable Int1 : Enable Interrupts 'Int1 optional (24MHz)
 Dim Temp_buf As Byte , Stat_buf As Byte

 1wreset
 Print Err ' optional
 1wwrite &H0C ' write status
 1wwrite &B01000010 ' continu convertion

Debut:
 1wreset
 1wwrite &HEE ' start conversion

 1wreset
 1wwrite &HAA ' get temperature
 Temp_buf = 1wread()

 1wreset ' optional
 1wwrite &HAC ' optional read status
 Stat_buf = 1wread() ' optional 82 when DS1821 run

 Print Temp_buf ; " " ; Stat_buf ; " " ; Tcon ' temperature is Temp_buf

 Goto Debut
 End
'Note that int1 pin is used because of the 24 Mhz Crystal
'this slow-down the communication (with out Isr code) just enough.
'make sure Tcon.2 (IT1) remain zero. if not [ Reset tcon.2 ]
'with a 12 MHh crystal any pin can be used and no need for interrupt.

' DS1821 pin1 = Gnd / pin2 = data in/out / pin 3 = +5v
' tested on Bascom-8151 + Bascom Lt