crw-rw---- 1 root dialout 204, 64 Aug 24 16:30 /dev/ttyAMA0 crw-rw---- 1 root dialout 4, 64 Aug 24 16:30 /dev/ttyS0 lrwxrwxrwx 1 root root 5 Aug 24 16:30 /dev/serial0 -> ttyS0 lrwxrwxrwx 1 root root 7 Aug 24 16:30 /dev/serial1 -> ttyAMA0
It is recommended to use /dev/serial0 in all cases if serial communication should go by GPIO14(TX) and GPIO15(RX).
If Bluetooth is activated the system will use /dev/ttyAMA0 to communicate with it.