Wanting to control a split flap display that was not near a
computer [Tom] looked to a common solution for communicating
over distances not practical for I2C or SPI. He developed his
own hardware and packet format using the RS-485 protocol. This
is part of a larger project he has been working on to feed data
to a split flap display that he plans to hang on the wall.
RS-485 is designed to work over long distances and overcome
noise issues. The core of the communications system is the board
seen on the left. It uses a MAX1483 chip, a pair of RJ45 jacks
for Ethernet cables, and two terminal blocks for power and
communications. There are a few nice things about this. The
board acts as a pass-through making it easy to chain nodes
together, and the data structure is completely independent of
the hardware itself. Because of this [Tom] developed his own
packet format that will be a bit more resilient than the Arduino
networking scheme we looked at the other day.