USM-110 User Manual 26
3.3.2 UART
Users can access the Android/Linux UART serial ports via tty-devices. The tty-
devices have different names depending on the UART driver on different boards.
RS-485 uses half-duplex communication, which means that one medium is used for
transmitting and receiving data. Therefore, the RS-485 transceiver transmit mode
must be controlled. Typically, the UART RTS signal is used to switch the transmitter
on and off.
COM Name Device Node Remark
UART0 /dev/ttyS0 for BT data
COM1 /dev/ttyS1
COM2 /dev/ttyS2 Debug port/RS232
COM3 /dev/ttyS3
COM4 /dev/ttyS4 Support RS-485/422