I used a Raspberry PI 3 directly connected to the Aruba AP-315 and was successful at getting into the console.
1. sudo raspi-config -> Interface Options -> Serial -> Would you like a login shell? (NO) -> Would you like serial port hardware? (YES) -> Finish -> reboot
2. sudo apt install minicom
3. Connect the following
Aruba pwr -> GPIO1 (3.3V)
Aruba grnd -> GPIO6 (GND)
Aruba TX -> GPIO10 (RXD0)
Aruba RX -> GPIO08 (TXD0)
4. minicom -b 9600 -o -D /dev/ttyS0
You should be in!