I finally finished wiring the LED displays on the breadboard prototype. What a mess!
The LTP-305HR displays are still being driven basically statically, with only one column of LEDs (on both logical rows) being illuminated at a time, and only changing at a very low rate. I still need to write Microblaze code to set up the timer for a 15 kHz interrupt and drive it from that for proper multiplexing.
After that, it will be time to write the VHDL to control the display entirely in hardware.
Since I’m confident that the display drivers work, I can start laying out the PCB now.
There is more variation in display intensity than I’d hoped, dependent on the number of LEDs illuminated in in a column. This is probably due to not really having enough voltage to work with. It’s not ideal, but the only practical alternative would be to require an additional power supply. A 6V supply would probably be fine. The higher the voltage, the more power the sink drivers have to dissipate.