Proton Tutorial - DS18S20

Device 16F877
XTAL 4
 
Declare LCD_TYPE ALPHA              ' Type of LCD Used is Alpha
 Declare LCD_DTPIN PORTB.4           ' The control bits B0,B1,B2,B3
 Declare LCD_RSPIN PORTB.2           ' RS pin on B4
Declare LCD_ENPIN PORTB.3           ' E pin on B5
Declare LCD_LINES 2                 ' Amount of LCD lines
Declare LCD_INTERFACE 4             ' Interface method is 4 bit
 
PORTB_PULLUPS = true
ALL_DIGITAL = TRUE
 
SYMBOL DQ = Portb.0                 'Place the DS1820 on bit 1 of PORTA
 
Dim Sign as Byte
Dim Cnt as Byte
Dim Count_Per_Deg as Byte
Dim Temp as Word
Dim Temp_Dec as Byte
 
Delayms 150                         ' Let LCD warm up
 
Cls
 
' Send a command that creates the degree
Print $FE,$40,$06,$09,$09,$06,$00,$00,$00,$00  
'  symbol on the LCD, to print it, simply address
'  the character as 0, eg,
'  Print At 1, 1, Value, 0, "Degrees"
 
Again:
 
'Send calculate temperature command
OWRITE DQ, 1,[$55,$10,$31,$C5,$C8,$00,$00,$00,$F4,$44]            
                 ' FF  I1  I2  I3  I4  I5  I6  CRC                 
                 '  FF - Family, Ix - Address bytes,
                 '  CRC - checksum
REPEAT
     DELAYMS 25                   ' Wait until conversion is complete
     OREAD DQ,4,[Cnt]             ' Keep reading low pulses until
UNTIL Cnt <> 0                    '  the DS1820 is finished
 
'Send read scratchpad command
OWRITE DQ,1,[$55,$10,$31,$C5,$C8,$00,$00,$00,$F4,$BE]            
                ' FF  I1  I2  I3  I4  I5  I6   CRC
                '  FF - Family, Ix - Address bytes,
                '  CRC - checksum checksum
 
OREAD DQ,2,[Temp.LOWBYTE,Temp.HIGHBYTE,Cnt,Cnt,Cnt,Cnt,Cnt,Count_Per_Deg]
 
' Each Cnt is 1/16 of a degree, therefore 100/16 = 6.25, and that's our decimal value
Temp_Dec = (6.25 * Cnt)      
 
' Bits 8-15 are 1 for a negative temperature and 0 for a positive
If Temp.8=1 Then
     ' If negative then drop the first bit, and invert the value      
     Temp=(Temp.LowByte ^ $FF) >> 1    
     ' If Cnt = 0 then increment Temp, as the 1820 does not do this
     If Cnt = 0 then Temp = Temp + 1    
     ' Change the sign to a negative
     Sign = "-"                                                           
Else
     ' If positive then drop the first byte
     Temp=(Temp >> 1)   
     ' And change the sign value to positive               
     Sign = "+"       
 
     ' Invert the decimal value                                                   
     Temp_Dec = 100 - Temp_Dec                             
Endif
 
' Display the data on the LCD
Print At 1,1, Sign, Dec Temp, ".", Dec DIG Temp_Dec, 1, 0,"C "
 
 
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