I'd like to start implementing a system consisting of 3 microcontrollers, but I would like to know the possibilities to let them communicate one with the other.
Ideally, 2 microcontrollers are acting as slaves, while the last (the "master") one is connected to a PC via RJ45. The problems I have right now is how to connect these 2 microcontrollers to the "master". The slaves MCUs perform very simple tasks (turning on/off a LED).
Ethernet communication is certainly possible (typically the Microchip Ethernet interfaces use SPI back to the MCU; just make sure the MCU has enough FLASH and data memory for the IP stack) and will allow any to talk to any other.
However, as intimated above, Ethernet can be a bit of 'overkill' depending on what information is required to be exchanged.
Using the UARTs on the MCUs will allow the master to talk to the slaves simultaneously (if needed). If you only have 1 SPI interface on the master then you can select the slave to communicate with using the \CS\ that is unique to eac slave.
Susan