Electronic – Is BeagleBone Black a microcontroller or computer

Simple enough. Pins 1 is the SPI Chip Select (GPIO). 2 - 4 are SPI data and clock pins. RST is an active low input (to the ENC28J60) so any GPIO can be used. INT and WOL are active low outputs (from the enc), so a GPIO in input mode on the BeagleBone.

For the SPI pins, you want the p9 header pins 28-31, which are Chip Select, Data Out, Data In, Clock. Any GPIO will work for the other signals.

The BeagleBone Black has 3.3V logic level signals. Its serial ports are all 3.3V ports. UART0 is tied to the debug header, and is hard coded for the debug log from the BBB. It is not useful for standard communication between two devices.

You have two main options. Luckily, the BBB has multiple UARTs that can be enabled. Turn one of the other UARTs on and connect the appropriate pins from the expansion headers to the RPI. Since the RPI defaults to a UART shell on the serial port, you can ssh into your BBB and then use minicom or similar to talk to the RPI from there.

_{Alternatively, you can use a USB serial cable on the BBB's USB Host port (or OTG if you needed to). AND you can also do the same on the RPI (so you have two usb to serial cables connected together), but that would require some setup on the RPI, a catch 22.}