Found this one myself -
http://en.wikipedia.org/wiki/SDI-12 -
"all SDI-12 communications are transmitted in ASCII at 1200 baud with 7 data bits and an even parity bit."if you use Serial.begin(1200) you should be able to get data in, you need to strip off the parity bit and then you can strat interpret the bytes...
not tested but this could be the starter
NewSoftSerial nss(3,4); // use software serial so hardware serial is free for PC
void Setup()
{
Serial.begin(9600);
nss.begin(1200);
}
void loop()
{
if (nss.available() > 0)
{
int val = nss.read();
val = val & 0x7F; // strip of one byte
Serial.print(val, DEC);
}
}