I don't know what your message structure is, nor
what instructions you are following for conversion.
Most motes have >8bit converters so you should
get two bytes of reading. Maybe you are only
looking at the low byte and shouldn't shift it?
The sensors do need to be calibrated since they
are only approximate in their absolute values,
and the thermistor is on the circuit card where
heat from other components can be a problem.
Or maybe your room IS warmer than you think...
The "funny things" that happen with packets are
usually related to Java's insistance on using
signed ints everywhere, which judicious AND
masking usually fixes.
MS
Shuvo Debnath wrote:
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 <[EMAIL PROTECTED]>
Date: Sunday, June 3, 2007 3:09 am
Subject: Re: [Tinyos-help] Problem reading the temperature byte in TinyOS packet
To: Shuvo Debnath <[EMAIL PROTECTED]>
Cc: [email protected]
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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