How to send data to SDI12 from Arduino

Kindly help, I want to send a combination of data from Arduino to SDI12 bus for Decagon. I am using Arduino SDI-12 Library.

This is the code I am using to send data:

void SDIsend( gps_fix & fix, int distance )
{
  if (fix.valid.time && fix.valid.location) {
    writeChar( fix.dateTime.hours, fix.dateTime.minutes, fix.dateTime.seconds,fix.lat, fix.lon, distance );
  }
}

and this is the error I get

'writeChar' was not declared in this scope

I am using Arduino Uno.

So, what scope IS writeChar() defined in?

I respectfully suggest that you take your snippets to http://snippets-r-us.com.