Expand the DS1820 library

[CS]

Hi David,

after a long test phase I found out, that it would be nice to have the possibility to get negativ or positiv sign before the temperature.
This information is stored in the DS18S20 Scratchpad Byte 1. If all bits are 0 then we have a positive temperature and when all bits are 1 then we have a negative temperature. So I overloaded the GetTemp function with the following:

Code: Select all

{
****************************************************************************
* Name    : GetTemp (OVERLOAD)                                             *
* Purpose : Read the device temperature  (pSign = 0 means negativ)         *
****************************************************************************
}   
Public Sub GetTemp(ByRef pTemp As ShortInt, ByRef pFraction As Byte,ByRef pSign As Byte)
   OW.WaitForHigh
   ReadSP
   pTemp = FSP(0).AsWord >> 1
   pFraction = (FSP(0) And $01) * 5
   If (FSP(1)) = $FF Then
      psign = 0
   Else
       psign = 1
   End If
   
End Sub

Of course it would be possible to build a function 'GetTempAsStringWithSign' like the following:

Code: Select all

{
*****************************************************************************
* Name    : GetTempAsStrWithSign                                                    *
* Purpose : Read device temperature and return as formatted string with sign*
*****************************************************************************
}  
Public Function GetTempAsStrWithSign() As String
   Dim TempA As ShortInt
   Dim TempB, Sign As Byte
   Dim s As String
   
   GetTemp(TempA, TempB, Sign)
   If sign = 0 Then
      s = "-"
   Else
      s = "+"
   End If
   
   Result =  s + DecToStr(TempA) + "." + DecToStr(TempB)
End Function

I can't test the last function because the testprogramm run into the demo limit.

Maybe you would integrate it in your next update!?

Best wishes

CS

[David Barker]

Nice to see you are getting to play will the compiler.

According to the DS18S20 datasheet...

"The temperature data is stored as a 16-bit sign-extended two’s complement number in the temperature register"

So you shouldn't need to do what you are doing as pTemp is already a signed number.

You also shouldn't need an explicit "-" symbol, as the DecToStr() routines will add this for you, if needed. For example...

Code: Select all

include "usart.bas"
include "convert.bas"

dim SignedNum as shortint

SetBaudrate(br19200)
SignedNum = -10
Write(DecToStr(SignedNum), 13, 10)

[David Barker]

I've posted a short article on the wiki showing how you can use Swordfish to connect to multiple OW devices of the same family...

http://www.sfcompiler.co.uk/wiki/pmwiki ... B20Article

[CS]

Thanks David,

it seems that I have overread the part with the 16-bit sign-extended.

CS

P.S.: Because of my starting problems with the OW-Devices I think it is a good idea to post an article on the wiki. Great !