Over the weekend I made this upgrade to my serial LCD back pack so that each LCD is assigned a unique address and only responds to messages sent to its own address. This way you can connect multiple LCDs, up to 254 of them (expandable to infinite number but what is the use of that?!). You can set the LCD back pack to respond to everything, or set it to only respond to messages sent to its own address and broadcast messages (address 255).
This is a result of a post that the OP wants to connect up to 100 LCDs together:
Here is a picture:
The top LCD has address 1 and the bottom has address 2. First I sent out a broadcast address (255) with a message:
Then I sent a message bound for screen 1:
"Screen 1 reporting!"
And only screen 1 is displaying it.
Finally I sent a message bound for screen 2:
"Screen 2 reporting!"
And only screen 2 is displaying it.
You can connect any number of displays to one serial port as my picture shows, only one FTDI USB TTL serial adapter I did have to use a separate power supply to power the two displays since the adapter is not providing much power.
If I disable the addressable features, then both LCDs will display identical messages except one screen is smaller and the other is bigger.