I am trying to modify an existing flux station (measuring at 10Hz) to incorporate an SDI-12 water quality sensor that only needs to measure every 30 minutes. I had hoped it would be a simple matter of plugging into the SDI-12 port and calling the sdi12recorder command. However documentation that I've found online indicates that I need to do the SDI-12 measurements in a 'slowsequence' section of the program, and that the SDI-12 port (port '0') is not compatible with slowsequence. When I pull up the help menu in crbasic for the sdi12recorder command, it says that it can use control ports 1, 3, 5, and 7. (Why only odd numbers?) But when I try to compile using port 5, I get an error saying that I must choose a port from 0 to 4. Currently control ports 1 and 3 are already being used for flux sensors. Is it possible that crbasic numbers the ports differently so that I need to say '3' to get control port '5'? Or what do I need to do in order to get this to work?