This is my proof-of-concept for using mqtt with the esp8266. I saw this LED display sitting around and I couldn’t imagine why no one was using it, the answer was no one knew how to talk to it. Easy, I think. Looking at the board it’s just an 8031, a serial level shifter, and a bunch of display-centric parts. The pile of capacitors around the max232 equivalent was the give-away. capacitors external to the chip are needed in the voltage boosting/negative voltage generation circuits for rs232 levels (until recently, I hear someone put them on-die). Tracing those signals is easy and I found they went to UART pins on the 8031.
Details at Evan’s Techie-blog.