BulletMagnet83:
Thanks for the replies so far!Unfortunately I don't own a TTL/USB converter, although it is on my shopping list. Is there any way I can modify an Uno board to accomplish the same thing? Like pulling the MCU out so the 8U2 HAS to talk to whatever I've wired up to the Tx/Tx pin headers?
I did remember about the blanking pin :-)) I've got the display to light all segments using synchronous mode so I'm fairly confident the hardware actually works, and the fault lies with me.
If you remove the MCU from arduino and connect TX to TX and RX to RX, you will be using the 8U2 (or 16U2) TTL USB adapter on the UNO board to connect to PC.