From Left to Right

Raspberry Pi  4B 8GB with T-Cobbler
Bi directional Logic Level Converter (BD-LLC), little red IC
Arduino 4: Arduino Hero  (Arduino master until BD-LLC is configured)
Arduino 5: Arduino Hero
Arduino 6: Arduino Hero
Arduino 7: Arduino Mega 2560
Arduino 8: Arduino Mega Wifi
Arduino 9: Arduino Uno R3
Arduino 10: Arduino Hero
Arduino 11: Arduino Hero
Arduino 12: Arduino Hero

 

Below is the first setup files to get the Raspberry Pi and Arduino devices to communicate on the I2C Bus.   Raspberry Pi is the master with all the Arduino devices as slaves.  I am sending a simple command to turn on LED 13 for 2 seconds and then off moving from Arduino 4 to Arduino 12. 

INO files for Arduino device

pi@raspberrypi:~ $ i2cdetect -y 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: — 04 05 06 07 08 09 0a 0b 0c — — —
10: — — — — — — — — — — — — — — — —
20: — — — — — — — — — — — — — — — —
30: — — — — — — — — — — — — — — — —
40: — — — — — — — — — — — — — — — —
50: — — — — — — — — — — — — — — — —
60: — — — — — — — — — — — — — — — —
70: — — — — — — — —
pi@raspberrypi:~ $