Template:RK3399-HWAccess
From FriendlyELEC WiKi
1 Access hardware
1.1 Access Serial Interface
For now only UART4 is available for users:
Serial Interface Serial Device UART0 Used by Bluetooth UART1 Used by Gbps Ethernet UART2 Used by Serial Debug Port UART3 Used by Gbps Ethernet UART4 Available, device name is /dev/ttyS4 (note: this is only applicable for ROM released after 20180618)