Could you please look at porting the code to the new Arduino R4 UNOs? They use a different chip (Renesas RA4M1 (Arm® Cortex®-M4)), and I cannot get SDI-12 code to compile for those board definitions.
Reading the preceding posts, I saw you use a software UART for the communication. The R4 UNO has 2 hardware UARTS, but another plus is that the built-in softwareSerial library supports customizable parity, stop and data bits. We were able to configure a couple of new ultrasonic water flow sensors with UART output available from Mouser and Digikey for around $30 to $60 each. This promises to be a huge improvement for our remote instruments that always required cleaning the Hall effect flow sensors due to debris clogging them. Neither has Arduino support yet, but we were able to reverse engineer some of the python code of one of the evaluation kits and get them to work with Arduino R3 and R4 UNOs. I would be happy to share our research and product links.