You've got 5 wires going into the board. Start with finding out which ones are power and ground.
There is also an LED for illumination. Find out (follow the traces) if it is always on, controlled by an IC on the board or by one of the 5 wires.
All unidentified wires: Trace them and see if they go into the IC under the black blob.
Protocol to control that IC can be I2C, RS232, SPI, or something propriatary.
If you can probe the wires while its operational, check them all.
If it toggles regularly, but low-frequent: Its a chip select.
if it has regular, but short spikes: Its either an acknowledge or an frame-sync
if if toggles fast but regular (fixed frequency, 50% duty cycle): its a clock
if it toggles irregular, its data.
"Regular", "infrequent" and "short" are all relative to the other signals.
Lookup patterns of I2C (clock+data), SPI(clock+data+chip select), RS232 (only data) on the internet and you'll see that you can easily identify them.
Once you know the protocol, deduce the data being sent. Correlate that to the image produced and you'r done!