Once the app is connected to the receiver, it can be configured by setting its parameters in Device > Set up receiver.
Each supported brand and model have a set of specific forms where modifying these parameters and send the configuration to the receiver.
Usually, GNSS receivers can be configured in two modes: base or rover, and each one can establish different types of data links, depending on the capacities and hardware available.
The contents of:3.4 Configuration of the external receiver
