I started with a simple Victron Blue Solar solar controller, then added a wall mounted monitor gauge connected by a VE direct cable. I have now moved onto the RPi Venus and have connected the solar controller to the Rpi with a VE.Direct/USB cable. That leaves me with the no spare socket on the solar controller to connect to my old wall mounted monitor. Is there any way of activating that monitor gauge other than to fill a hole in my van. Bluetooth dongle?
If your monitor just receives the serial data from the MPPT, then it can be paralleled with the input to the RPi. ( you will need to make a special cable for this.) IF it interrogates the MPPT for the data, then this will not work. In either case, you may be better off filling the hole, and using the GUI from the R-Pi.