Emoncms+RFM2Pi+TinyTX DS18B20 negative Temp´s error

Hi,

i´m running emoncms on a Raspberry Pi with RFM2Pi connected to the Uart´s.

All works fine...except negative Temperatures.

They will come as Numbers larger than 63000.

time                 data
1388868555 21.62
1388868615 14.37
1388868676 652.36
1388868676 652.36

On the PI run´s the rfm12piphp gateway service.

When I parse the incomming Data with the perl gateway Script serial.pl

all Values are displayed right.

17 157 5 220 11
Temperature 14.37
Battery 3036
17 212 254 195 11
Temperature -3
Battery 3011
-> 4 b
17 124 252 156 11
Temperature -9
Battery 2972
-> 4 b
17 24 251 124 11
Temperature -12.56
Battery 2940
-> 4 b
17 61 250 94 11
Temperature -14.75
Battery 2910
-> 4 b

I find out that the Data is right but only parsed as the positve Number. 

decimal
64311
decimal (formatted)
64,311
hex bytes
FB 37
hexidecimal
FB37

Negative number -1,225 (two's complement hex 0xFB37)

How can I fix this ?

Sorry for my bad english

mattes