The heart of all the system is the PIC. I have used various models, based on my requirements. Many typologies of PIC can be used because they have at least one USART integrate, I have tried the 16F88, 16F876,16F628 all work perfectly, also using the oscillator inside(16F88). In the code attached I make reference to 16F628 which it manages all the protocol and the interface with the outside through its doors of entrance/exit. For the physical transfer of the data comes in aid a RTX of common use in nets CAN which the MCP2551 or Maxim, MAX3050 and others of the same family. The use of this RTX simplifies the SW because the commutation rx-tx is automatically managed from the chip.
The protocol is completely various from the Can-Bus and imagined to use the PIC resources, simplifying it to the maximum maintaining like priority irrenounceable reliability of the data received.
The BUS physic is composed from 4 spin in which the 2 pass the data and 2 the current. The disturbs' immunity it's given from the type of transmission differentiates used also in industrial area.
The transmission type is asynchronous 38400bps 8N1, the speed can be easily increased or decreased without no one type of inconvenience software to part the maximum distance that varies.
The particulars CAN speak approximately 1Mbps max 40 meters, 115200bps 600metri max and so on, for the informations see CAN BUS