I was having trouble running PiStar on RPi3 with a DVMEGA/Bluestack on USB0 and Nextion on USB1. The DVMEGA runs fine without the Nextion. When both are plugged in the DVMEGA can't initialize and mmdvm host just cycles up and down. I have to actually configure the display to None to get the DVMEGA back. PiStar runs fine with Nextion on USB0 if I connect the DVMEGA to the GPIO eliminating the Bluestack.
The following solution came from Brad Kellison in the PiStar Facebook Group: Not enough current from the port to run both. Try a separate supply for the display.
Brad, thanks for this suggestion. I was surprised to see how low the Pi voltage was even without the display. I did not suspect voltage since the DVMega worked with the display if it was on the GPIO. I forgot that the Bluestack also had an Arduino inside. Some power supplies are horrible, Some cables are horrible too. I finally found a single power supply and cable combination that sustains 5.0v at the Pi and 4.9 at the display. The DVMega still would not initialize. I finally split the power for the Nextion screen from the USB source and powered the display independently. Sure enough everything came up as expected. This experience was an eye-opener to the inconsistencies between power supplies AND cables and the ability of the USB ports on the Pi to source current.
So if you are trying to run DVMEGA Bluestack on USB with a Nextion Screen on USB you probably will have to provide a second power supply for the screen.
DV-Mega Single / Dual band Hat for the Raspberry Pi
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