[Tinyos-help] Problem reading the temperature byte in TinyOS packet

[Shuvo Debnath]

Hi Michael,

Thanks for the response. Unfortunately it did not seem to fix the problem!  I was doing a bitwise AND operation originally, but that was giving me very large results.   

An example output of my listener using bitwise logical AND with 0xFF is:

HexRawTemperature=d5  IntRawTemperature=213   (I printed both hex and int to make sure it was not a signing issue)
adjTemp=852.0  (value after binary shifting packet[18] by 2 places to the left, as instructed in the documentation)
Converted Temperature in Celsius = 62.624563   (Definitely not my room temperature!)

Would you have any other suggestions? Does WindowsXP or Java do anything funny to packet streams?  

Thanks,
Shuvo 





----- Original Message -----
From: Michael Schippling <schip at santafe.edu>
Date: Sunday, June 3, 2007 3:09 am
Subject: Re: [Tinyos-help] Problem reading the temperature byte in TinyOS packet
To: Shuvo Debnath <Shuvo.Debnath at student.uts.edu.au>
Cc: tinyos-help at Millennium.Berkeley.EDU

> I think what you probably want is a Bitwise (not Logical) AND:
>     packet[18] & 0xFF
> 
> What you may be seeing is Java's attempt to help you by promoting
> a byte that we wish was unsigned to a signed int.
> 
> MS
> 
> Shuvo Debnath wrote:
> > Hello, 
> > 
> > I am using a mica2 mote and MTS310CA sensor running XServe, and 
> am trying to read in the temperature byte.  I have read all the 
> documentation, and using Java, my function that converts a raw byte 
> -> temperature works 100%, I tested this thouroughly. However I am 
> having trouble actually getting the correct raw byte.  When I read 
> in the documented byte (18th in packet) I should be getting a value 
> between 110-130 to correspond to room temperature (19-23 degrees 
> C).  
> > 
> > However, instead I get very small numbers: Such as 2 or -13 
> depending on which sensor I read (I have multiple MTS310).   I 
> tried running the sensors against MoteView and the results are all 
> accurate, so it is not a hardware issue. 
> > 
> > I suspect this is a Java issue but I am not sure. Does anyone 
> have any suggestions? I need to get problem solved fairly quickly 
> due to a very imminent deadline!  
> > 
> > If it helps, I am reading the packet by simply doing a:
> > 
> > byte[] packet= reader.readPacket();
> > if(packet.length==32)
> > System.out.println("For Node:" + packet[7] + 
> "RawTemperatureReading=" + packet[18]);
> > 
> > A logical AND between the raw byte and 0xFF gives more extreme 
> results (250+ on one sensor and < 10 on others). 
> > 
> > Thankyou in advance,
> > Shuvo
> > 
> > 
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