Spencer,
A 5 inch absolutely needs its own power supply. Using the onboard 7805 will result in thermal shutdown. (been there... it appears to work for a while... then screen blanks, reboots, or other bad things). The "all zeros" on your display means that the Nano and the Nextion are not talking (I assume that when you tiddle the VFO, nothing happens?) The "not talking" can happen if the nano and the Nextion dont boot in a certain order. It can also happen if you reverse the blue and yellow wires.?
All your symptoms point towards inadequate PS amps. (I don't think USB can provide the amps needed by a 5" screen). Find a buck or an inexpensive ps on Amazon and put that Nextion on it. Bet ut wukk work fine.
73
Mark
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AJ6CU
KD8CEC 2.0, Nextion Screens,? and open source uBITX Raduino boards for Arduino IOT, BLE, RP2040, Teensy 4.0, and Raspberry Pi Pico
https://github.com/aj6cu
