Well, I received my 2nd display today and of course had to wire it up. 1st I had to verify the display was good which of course it was. It displayed the message just as the first did.
Then came the fairly easy task of extending the display from 40 to 80 columns.
The electrical connections were pretty straightforward. I simply took all the power connections at the banana plugs from the 1st display and tied them to the second. So GD went to GD, 5D to 5D, 5L to 5L and GL to GL. I then took an old hard drive ribbon cable and jumpered from J2 on the 1st display to J1 on the second. This puts the second display to the right of the first. At this point the value of the higher current 5V supply for the display power is even more important so if you attempt this, make sure your supply is adequate.
The last thing to do was to make a few changes in the code from the 40 to 80 column.
I’ve included the source for the 8×80 display here.