Communication protocol between CAN and CC2540 chip. [[BR]]

List of commands from CC2540 to CAN transiver: 
 1. Subscribe to a message
 2. Unsubscribe from messages
 3. List of all subscriptions 
 4. Passthrough message  

Command message structure
 1. Command code (1 byte)
 2. Payload size (1 byte)
 3. Payload (0 - 255 bytes)

Examples
 0x01:0x08:0x00:0x00:0x07:0x06:0x00:0x01:0x05:0x05
 1. byte - subsribe command
 2. byte - payload size 8 byte = 2 CAN message IDs * 4 byte each