I have a Pi Zero that I would like to use to communicate with a B+. In theory I can connect an adaptor cable and a WiFi or Ethernet USB dongle to the Zero, and do the same on the B+.
However, as an alternative, it is theoretically be possible to connect the two together either using USB or GPIO (e.g. off the top of my head, using PPP over the serial).
I would imagine the following may exist:
USB to USB (with special hardware & kernel drivers) - up to 400 Mbit/s
Serial to Serial (e.g. PPP) - up to 3.5 Mbit/s (Raspberry Pi: Increase UART speed)
SPI (with additional hardware) - ?? Mbit/s
I2C (with additional hardware) - 30 Mbit/s (What bitrate can I get from an i2c bus?)
Bit Banging GPIO - ?? Mbit/s
USB/Ethernet - 400 Mbit/s - e.g. with a USB 2 Gigabit Ethernet Adaptor - are there any already supported by the kernel, or use pi compatible drivers?
Could you confirm if they do exist, and if there are mature implementations (e.g. can be relatively easily used to transfer IP datagrams).
I am looking to implement a backup camera (camera on the zero, screen on the B+) so would need to transfer a fair amount of data fairly quickly.