I2C Multiplexer 4 - V2
This is a I2C 4 bus multiplexer based on the TCA9545A chip. Lots of optional pull ups via jumpers. Each channel can be either 3.3V or 5V selectable via jumper. Resets are also isolated via MOSFET. Channels can be powered from the master bus or an alternate supply. It can be mounted in a standard 72mm DIN carrier.
I designed this to be used with my NanoPi NEO Adapter - V3.
A PCB of the multiplexer can be ordered from OSHPark. (As of 2018 ~$45US for 3 boards)
The schematic is available here.
The I2C connector is documented at Standard Connector for I2C.
Many components are SMD although reasonably large and easy to work with. Resistors, most capacitors, and LEDs are 1206 size.