Hardware serial on soligen2010 dspmeter

[koolcat6666]

I do not understand your decription to use hardware: you Say to use pin 0 (i understand D0) to Connect nextion display instead pin 9 ( i understand D9), but D0 is serial rtx and is already used to connect raduino board to the second nano. So Nothing is going from dsp to nextion but signal from raduino. Am i wrong? Can you explain this better? Do i have to wire radunino and Nextion display on the same pin (D0) on second nano, Wire both on the same pin, Or do i have to use use D1 hw serial tx?