In SX Microcontrollers, SX/B Compiler and SX-Key Tool, Dunnsept wrote:

OK.. final work around without using tables at all.. 

note: YMMV, this works for me and is accurate enough. this is also obviously not complete code

  

[code]
check_cj_temp
read_tc
temp = TC_LSB \ 5
temp = temp * 2
theTEMP = cj_temp + temp 


get_cj:
 owwrbyte tempin, skipnet
 owwrbyte tempin, rdreg
 owwrbyte tempin, $18
        owrdbyte tempin, cj_temp
 owrdbyte tempin, tcuvb
      
return 

check_temp:
  owreset tempin,temp1
  owwrbyte tempin,skipnet
  owwrbyte tempin,rdreg
  owwrbyte tempin,$0E
  owrdbyte  tempin,  TC_MSB
  owrdbyte tempin, TC_LSB
  sign = TC_MSB.7                             ' save sign bit
  TC_LSB = TC_LSB >> 3  
[/code]
[/code]
TC_LSB is the lsb returned from the DS2760 after adjusting the 12 bit data. cj_temp is the MSB from checking the cold junction temp.

I put together a speadsheet of the calculations to compare to the real K type table and the values are really close. looks like maybe +- 0.5 or so

sometimes it's right on. 

I know that thermocouples are not linear but for the ranges I want this is really close and sure beats having to deal with all those table lookups ;-)

 

BTW: the heat sink on my regulator on the SX tech board is 113F whilst my office is 71F  isn't it wonderful the things you can discover with thermocouples? :p   :p

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