Connect multiple Nextion displays

It is perfectly possible to connect more than one display to your MMDVMHost hotspot or repeater.

But there are some things you should take in account !

Provide enough power

On the 'where to connect my display' page, it is already mentioned : take care of the power supply.

You have to power your host (Raspberry Pi, orange Pi, banana Pi, Pi zero, ...). Check the specifications to be sure to provide enough power of good quality. Bad powersupplies are source of many problems ! Your device may run unstable, reboot, ... Again : use a good power supply !

Make the calculations. Power for the host + power for the modem + power for the displays. And then add some serious reserve.

For the RPi, check the Power Supply page and the Power chapter fo the FAQ page.
The latter also specifies the maximum power you can draw for your USB peripherals (i.e. USB/TTL convertor).

So the bottom line is: provide enough good quality power. And before you think : 'OK, OK, you just said that several times', please don't say I didn't warn you.

If necessary, you can provide the power to the Pi (or wathever host you have) with one power supply and use another power supply for powering the displays. Do not forget to connect the GND of both. Only the GND. Not the +5V.


Just some displays in parallel

When you just want to display data and you do not need to use the touch buttons commands to the host on the display, you just connect the displays in parallel without connecting the display TX lines (blue wire).




You could also connect ONE blue wire, from the display where you want to use touch buttons sending commands to the host.
But connect ONLY ONE display to the RX of the host.





One display connected to the modem and one to the host

Another possibility is to connect one display to the modem and one to the host.
This is only possible when using my NextionDriver AND you configure MMDVMHost and NextionDriver the right way:

  • configure the NextionDriver to use the host-connected display (/dev/ttyAMA0, /dev/ttyUSB0)
  • activate the Transparent Data option for MMDVM

The NextionDriver will send all data to both the displays.

When the modem is able to return data to MMDVMHost, it is possible to use touch button commands to the host on both displays (but at this time, most modems don't send data back to the host).


Merge displays

When you want to connect multiple displays and all displays must have the possibility to send commands to the host, you have to 'merge' the data from the display to the host. This can be done by using some TTL logic. But it also can easily be done by using some diodes (this can be any small signal diode i.e. 1N4148).

Note that, if you touch a button that sends commands, the host will not know which display sends commands. But even then, all displays share the communication channel, so all data goes always to all displays.