I have a Lumagen 2021 scaler, and notice that strange things happen to
it when I have it connected via USB-RS232 converter on my PC, and
start up either HCFR or displayCAL, around the time those apps try to
discover their list of meters.
I am guessing there is some serial chatter related to discovering
meters which have a serial interface which is being interpreted by the
Lumagen, which has a very simple command structure.
It would be nice to either be able to make these apps or Argyll ignore
a particular serial port (maybe already possible and the app writers
need to allow the option), or alternatively to check if it is a
Lumagen and don't do anything else to it.
Lumagen RS232 spec is here: