Reply To: Problems with a combined MH21 Gen1 and Gen2 station

The only difference between the Gen 1 and 2 Hydros21 sensors is that the Gen 2 sensors need a little more time to respond to the SDI12 measurement command, which is hardcoded into one line in the MeterHydros21.h file within the ModularSensors library.  If you’re using the most recent version of ModularSensors, then your code will support both generations of sensors.  But the SDI12 library is a separate library from ModularSensors and is very complex and handles things like interrupts and timing that can break if not used correctly, or it could also conflict with other libraries or functions if they’re not compatible.  I didn’t check the rest of your code, but I’ve successfully used over a dozen Hydros21 sensors simultaneously with one Mayfly board before with all the sensors connected to D7, but the most important thing is to verify that each sensor has had its SDI12 address changed individually to a unique number prior to connecting them all to a logger with a sketch that is communicating with all of them at once.