How come my DS18S20 code still works?

[Wilson]

Hello Jerry.

Excellent explanation. Now I understand it a lot better.

You are right, I really do not need that much accuracy but it was good to find out how it can be done.

Thanks very much.

Wilson

[mystified]

my code just gives me the same output, I'm trying to use 4 7 segment displays can you all help me I am useing a 18f452
clear
define osc 20
include "modedefs.bas"

trisa=%11111111 ' a as input
trisb=0 'port b as output
trisd=%00001111 'portd as output 7-4 & 0-3 as input
digit var byte
pattern var byte
digit1 var portd.7
digit2 var portd.6
digit3 var portd.5
digit4 var portd.4
'DS18S20_9bit con %00011111;93.75ms,0.5c
'DS18S20_10bit con %00111111;187.5ms,0.25c
'DS18S20_11bit con %01011111;375ms,0.125c
DS18S20_12bit con %01111111;750ms,0.0625c default

i var word
DQ var PORTA.4 ' one wire data pin

Temp_C var word
SignC var word
Busy var byte
Negative var word
Positive var word

Temper var word
count_remain var byte
count_per_c var word


digit4=0
digit3=0
digit2=0
digit1=0



Start:
temper.lowbyte=0
temper.highbyte=0
count_remain=0

owout DQ,1,[$CC,$B4] 'test for parasite power or external supplies
pause 10 'wait for power test

owout DQ,1,[$CC,$4E,0,0,DS18S20_12bit]


owout DQ,1,[$CC,$44] 'start conversion

Waitloop: ' check for still busy converting
owin DQ,4,[count_remain]
if Count_remain=0 then goto Waitloop

owout DQ,1,[$CC,$BE] 'read scratchpad

owin DQ,0,[temper.lowbyte,temper.highbyte,skip 4,count_remain,count_per_c]

'calculate temperature in c to 2 decimal
temp_C=((( Temper>>1)*100)-25)+(((count_per_c - count_remain)*100)/count_per_c)
' 7 segment 4 led display


digit=Temp_C dig 3 'get 1000s
gosub convert
portb=pattern
digit4=0
digit3=0
digit2=0
digit1=1

pause 5

digit=Temp_C dig 2 'get 100s
gosub convert
portb=pattern
digit4=0
digit3=0
digit2=1
digit1=0
portb.7=1

pause 5

digit=Temp_C dig 1 'get 10s
gosub convert
portb=pattern
digit4=0
digit3=1
digit2=0
digit1=0
portb.7=0
pause 5

digit=Temp_C dig 0 'get 1s
gosub convert
portb=pattern
digit4=1
digit3=0
digit2=0
digit1=0

pause 5
digit4=0


goto Start

end


convert:
lookup digit,[$3f,$06,$5b,$4f,$66,$6d,$7d,$07,$7f,$6f],pattern
portb=pattern
return