Convert Hex binary string to a value in Rules

Setup, Configuration and Use Scripts & Rules
1

How can I convert a binary hex string to a value.

I read the string form a CO2 sensor (T6613) device by the serial binding. I have added -Dfile.encoding=ISO-8859-1 in Java args so the read and write of 8bit characters to the /dev/ttyS0 work ok.

I have an item
String RS_CO2 “RS_CO2 [%s]” { serial="/dev/ttyS0@19200" }

In my rule I have

rule "CO2 rs2232 wait for device"
when 
     Item RS_CO2 changed
then
    
       var rsstring      = RS_CO2.state.toString    // The string looks like this "\u00FF\u00FA\u0002\u0002\u008A"	 . The last 2 bytes hold the value
       var check         = rsstring.substring(1,2)      // Reads byte FA to test the answer is right
       var valuestring = rsstring.substring(3,5)     // Reads the value string from the string

       if (check == "\u00FA")  //  right measure 
       {
          var value =  ????????????(valuestring)
          postUpdate(CO2, value)
       }

end

I have tried many conversions, but they all take a hexstring as a starting point, not a binary hex string.

Can anyone give me a hint on this issue and replace the ??? by a function. This can’t be to difficult?

2

Some methods here that may be useful

3

Hello Rossko57

Thank you for your help, but the answer is somewhere hidden in all the discussions. But you gave me a new insight with your answer and I now have it done. Far to complex and waiting for a simple solutions, but it is working.

rule "CO2 rs2232 wait for device"
    when 
         Item RS_CO2 changed
    then

           
           var rsstring    = RS_CO2.state.toString	
           var check          = rsstring.substring(1,2)    // check value
           var valuestring = rsstring.substring(3,4)    // high 
           var valuestring2 = rsstring.substring(4,5)   // low
           
           var char [] array = rsstring.toCharArray()
           val StringBuilder sb = new StringBuilder
           array.forEach (b | sb.append(Integer::toHexString(b) + " "))   // readable string for debug
     
           var char [] array2 = valuestring.toCharArray()
           val StringBuilder sb2 = new StringBuilder
           array2.forEach (b | sb2.append(Integer::toHexString(b)))  // high
     
           var char [] array3 = valuestring2.toCharArray()
           val StringBuilder sb3 = new StringBuilder
           array3.forEach (b | sb3.append(Integer::toHexString(b)))  // low
     
            
           if (check == "\u00fa")  // check right string
           {
              var value = Integer::parseInt(String::format("%s",sb2), 16)  //high
              var value2 = Integer::parseInt(String::format("%s",sb3), 16)  // low
              var value3 = value * 256 + value2
              
              postUpdate(AD_CO2, value3)
              logInfo("CO2 rs 232", "String CO2 =" + sb + "value =" + value3 )

           }

    end

And it works with this brute force solutions.