' -----[ PrecTemp ]-----------------------------------------------------------
'This program uses the Dallas DS1620 temperature chip and returns a 
'temperature reading accurate to 1/10 deg Celsius. The routine uses 2
'undocumented codes for the DS1620. (read counter & Load Slope)
'The DS1620 has a little thermal mass and does not respond instantly to
'contact changes in temperature but it is very accurate. 
' The chip will actually heat up about 1/2 to 1 deg C in the first few
' seconds of operation due to the heat generated on the chip itself and
'the LP voltage regulator next to the chip.
  
'  BS2           DS1620
' -----          -------
' Pin 11         DS1620.3
' Pin 12         DS1620.2
' Pin 13         DS1620.1

True    CON     1
False   CON     0

' DS1620 pins
'
Rst     CON     11                       ' DS1620.3
Clk     CON     12                       ' DS1620.2
DQ      CON     13                       ' DS1620.1

' DS1620 commands
'
RTmp    CON     $AA                     ' read temperature
WTHi    CON     $01                     ' write TH (high temp register)
WTLo    CON     $02                     ' write TL (low temp register)
RTHi    CON     $A1                     ' read TH
RTLo    CON     $A2                     ' read TL
Strt    CON     $EE                     ' start conversion
StpC    CON     $22                     ' stop conversion
WCfg    CON     $0C                     ' write configuration register
RCfg    CON     $AC                     ' read configuration register
'non documented commands
RCnt	CON	$A0			'Read Counter Command
LSlo	CON	$41			'Load Slope Command

' -----[ Variables ]-------------------------------------------------------
'
cmdByte VAR     Byte                    ' command to send to DS1620
tmpIn   VAR     Word                    ' 9-bit temp input from DS1620
nFlag   VAR     tmpIn.Bit8              ' negative flag
hlfBit  VAR     tmpIn.Bit0              ' half degree C bit
RegIn	VAR	Byte			'DS1620 config register reading
CovDon	VAR	RegIn.bit7		'Conversion done bit done=1
CouRem	VAR	Word			'Count remaining register reading
COC	VAR	WORD			'Count per Deg C register
tempC   VAR     Byte                    ' converted celcius value
temp    VAR     Word                    ' temperature to display
sign    VAR     Byte                    ' sign of temperature
frac_d  VAR	byte			'1/10 th fraction of temp

        DirH = %00111000                ' DS1620 pins
        Outs = $0000                    ' all outputs off to start


' Initialize the DS1620
' - use with CPU in single shot mode
        HIGH Rst                        ' alert the DS1620
        cmdByte = WCfg                  ' prepare to write config
        GOSUB CmdOut                    ' send the command
        cmdByte = %00000011             ' with CPU; single shot  mode
        GOSUB CmdOut
        LOW Rst
        PAUSE 10                        ' pause for EE write cycle
        

' -----[ Main Code ]-------------------------------------------------------
'
Main:
        HIGH Rst			'Alert the DS1620
        cmdByte = Strt                  'Start temp conversion
        GOSUB CmdOut
        LOW Rst
  T1:   High Rst			'Alert the DS1620
	CmdByte = Rcfg			'read the configuration register
	GOSUB CmdOut			'to see when the conversion is done.
	Gosub Rconfig
	LOW RST
        HIGH Rst                        ' alert the DS1620
        cmdByte = RTmp                  ' read temperature
        GOSUB CmdOut
        GOSUB TempIn                    ' get the temperature
        LOW RST
	HIGH RST			'alert DS1620
	CmdByte = RCnt			'Read Count Remaining register
	GOSUB CmdOut
	GOSUB ReadCount			'get result
	HIGH RST			'Alert Ds1620
	CmdByte = LSlo			'Load slope command
	GOSUB CmdOut			'Loads Slope into counter Register
	LOW RST
	HIGH RST			'Alert DS1620
	CmdByte = RCnt			'read count remain reg for slope
	GOSUB CmdOut
	GOSUB CountC			'Get Count per deg C 
'************************************************************************
' Temperature = TmpIn - 0.25 + (CoC - CouRem)/CoC
'  Temperature = TmpIn - 1/2 deg bit + (Count per deg - Count remaining)/ count per deg
'************************************************************************

   '**************************************************************
ShowC:  GOSUB GetC                      ' convert to celcius
        temp = tempC
        GOTO ShowT

        GOTO Main


' -----[ Subroutines ]-----------------------------------------------------
' send command byte to the DS1620
CmdOut:
shiftout DQ ,clk ,0,[cmdbyte]     
   RETURN

' read 9-bit temperature from DS1620
TempIn: tmpIn = 0                       ' clear input variable
shiftin DQ, clk,1,[tmpin\9]        	'get 9 bit result
RETURN

'Read Config register for Conversion done bit 7  1=done
RConfig:  RegIn = 0			'reset register to 0
	Shiftin DQ, CLK, 1, [RegIn\8]	'get result
	LOW RST
	IF CovDon = False then T1	'if done bit not 1 do it again
  RETURN

'read count remaining register
ReadCount:  CouRem = 0			'Reset count remaining register
	shiftin DQ, clk, 1, [CouRem\9]  'get count remaining 9 bit
	LOW RST
   RETURN

'read count per deg c register
CountC:    CoC = 0			'Reset CoC register
	Shiftin DQ, CLK, 1, [Coc\9]	'get result 9 bit
	LOW RST
   RETURN

' convert reading from 1/2 degrees input (rounds up)
'
GetC:   IF nFlag = 0 THEN CPos          ' check negative bit (8)
        sign = "-"                      ' set sign
        tempC = -tmpIn / 2      ' if neg, take 2's compliment discard hlfbit
        GOTO CDone
CPos:   sign = " "
        tempC = (tmpIn & $FE) / 2 	'mask the half bit & convert to DEG C
CDone:  RETURN

showT:
frac_d  = ((CoC - CouRem) * 10)/ CoC ' deals with BS2's lack of floating point
'**************************************************
'data to lcd goes here if you are using a LCD display
'**************************************************
Debug DEC tempC, ".", Dec frac_d, "Deg C",cr,cr	'display temp to 1/10th deg

pause 1200				'wait a little while
  GOTO Main				' do it again

'Program by Pat Sweeney
'	   The Circuit Tree
'	   Tenino Wa