Now we finish 7 seg display temp form ds1820 about 90%
But we stil have porblem with display fashing and i have try at 20 Mhz cannot resolve it



Code:

Define LOADER_USED 1
DEFINE OSC 4
@ Device pic16F877A, xt_OSC, BOD_OFF, PWRT_ON, WDT_OFF, PROTECT_OFF 'WRT_On

Segments Var PORTC
Digits Var PORTD

i Var Byte
n Var Byte
Value Var Word

' Allocate variables
command var byte ' Storage for command
J var byte ' Storage for loop counter
temp var word ' Storage for temperature
T VAR WORD
DQ var PORTd.4 ' Alias DS1820 data pin
DQ_DIR var TRISd.4 ' Alias DS1820 data direction pin
read_done var byte
Lastdata var word


TRISc = $00 ' Set segment pins to output
TRISd = $f0 ' Set digit pins to output
TrisB = $00
Portb = $00
portd = $ff

DEFINE HSER_RCSTA 90h
DEFINE HSER_TXSTA 24h
DEFINE HSER_SPBRG 12 ' 19200 Bauds ,4 m
'debug ====

' Mainloop to read the temperature and display on LCD


mainloop:
'goto display
'Goto mainloop

Gosub init1820 ' Init the DS1820

command = $cc ' Issue Skip ROM command
Gosub write1820

command = $44 ' Start temperature conversion
Gosub write1820

Pause 2000 ' Wait 2 seconds for conversion to complete

Gosub init1820 ' Do another init

command = $cc ' Issue Skip ROM command
Gosub write1820

command = $be ' Read the temperature
Gosub write1820
Gosub read1820


'Display the decimal temperature
'HSEROUT ["Temp = ",dec (temp>>1),".", dec (temp.0*5)," C",13,10]
'T = ((temp>> 1)*100)+((TEMP.0*5)*10)
'HSEROUT ["Temp = ",dec T ,13,10]
value = ((temp>> 1)*100)+((TEMP.0*5)*10)
GOTO DISPLAY
Goto mainloop ' Do it forever


' Initialize DS1820 and check for presence
init1820:
Low DQ ' Set the data pin low to init
Pauseus 500 ' Wait > 480us
DQ_DIR = 1 ' Release data pin (set to input for high)

Pauseus 100 ' Wait > 60us
If DQ = 1 Then
'Lcdout $fe, 1, "DS1820 not present"
Pause 500
Goto mainloop ' Try again
Endif
Pauseus 400 ' Wait for end of presence pulse
Return


' Write "command" byte to the DS1820
write1820:
For i = 1 to 8 ' 8 bits to a byte
If command.0 = 0 Then
Gosub write0 ' Write a 0 bit
Else
Gosub write1 ' Write a 1 bit
Endif
command = command >> 1 ' Shift to next bit
Next i
Return

' Write a 0 bit to the DS1820
write0:
Low DQ
Pauseus 60 ' Low for > 60us for 0
DQ_DIR = 1 ' Release data pin (set to input for high)
Return

' Write a 1 bit to the DS1820
write1:
Low DQ ' Low for < 15us for 1
@ nop ' Delay 1us at 4MHz
DQ_DIR = 1 ' Release data pin (set to input for high)
Pauseus 60 ' Use up rest of time slot
Return


' Read temperature from the DS1820
read1820:
For i = 1 to 16 ' 16 bits to a word
temp = temp >> 1 ' Shift down bits
Gosub readbit ' Get the bit to the top of temp
Next i
Return

' Read a bit from the DS1820
readbit:
temp.15 = 1 ' Preset read bit to 1
Low DQ ' Start the time slot
@ nop ' Delay 1us at 4MHz
DQ_DIR = 1 ' Release data pin (set to input for high)
If DQ = 0 Then
temp.15 = 0 ' Set bit to 0
Endif
Pauseus 60 ' Wait out rest of time slot
Return
'================== 7 seg ment display ==============================
display:
'value = ((temp>> 1)*100)+((TEMP.0*5)*10)

PORTC = $39
LOW DIGITS.0
PAUSEUS 1500
PORTC = $0

'value = 125
For i = 1 To 4 ' Loop through 4 digits

n = Value Dig i ' Get digit to display

' Gosub display1 ' Display the value
Digits = $ff

Lookup n, [$3F, $06, $5B, $4F, $66, $6D, $7D, $07, $7F, $6F,_
$77, $7C, $39, $5E, $79, $71, $0FF], Segments

If i = 2 then segments = segments + 128 'Digit 2 show dot

Digits = ~Dcd i

NEXT I
goto mainloop
End