My ship has limited power. So I am creating three bus paths: Ground, 5V, and 3.3V. It will also help with the limited amount of wire I have. It is important to not have ground loops. Ground loop is an unwanted electric current path in a circuit resulting in stray signals or interference, occurring, e.g., when two earthed points in the same circuit have different potentials. The 9V-1A power supplies share the same ground. If you follow each ground path, they end without connecting back. I made sure both sides of each bread board are grounded
I will keep 5V and 3.3V isolated on the control boards. Still need to connect up the 3.3V. I will also not to create loops. Ground loops are very bad.
I connected the ground and 5V buses together around the control boards.
I2C uses SDA and SCL connections.
SDA: Serial Data: Data moves here
SCL: Serial Clock: Clock sync here
SDA : pin 20
SCL: pin 21
SDA: pin A4
SCL: pin A5
I checked each ground and power path with a multimeter to verify wiring. I split the power connections of the Arduino devices to separate locations on the boards. 5V is reading 4.99V. I checked for ground loops. I also wired to limit the connection lengths.
The bottom rows are I2C bus. On the control board by the Slave 4, You will notice some extra jumpers. I found that one of the control boards top and bottom rows were no longer connected left side to right side. I place jumpers on them to complete the circuit. I can now get 4.99V across the top row of red pins.
I was able to find a few SN74HC595N shift registers to connect the lighting up with. This saves on wire and ports of the controllers.
I found a 8 position dip switch. I need to find a shift register for them.