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3.4
UART
The Android/Linux UART/serial port access from user is through the tty-devices. The
tty-devices have different names depending on UART driver on different board.
RS-485 uses half-duplex communication, which means that one medium is shared
for transmitting and receiving data. Therefore the system needs to control the RS-
485 transceiver's transmit mode. Usually the UART RTS signal is used to switch the
transmitter on and off.
3.4.1
EPC-R4710 UART
COM Name
COM1
COM2
COM3
COM4
COM5
COM6
3.4.2
How to Configure RS232 or RS485 Mode
Enter U-boot interrupt mode.
Connect device to debug port, and open debug console.
Press "ctrl + c" key before power up the device, until get the following information on
debug console:
Hit any key to stop autoboot: 0
=> <INTERRUPT>
=>
Then you can input the following command to config UART mode.
RS485 Mode:
setenv uart_mode 0x0c
saveenv
reset
RS232 Mode:
setenv uart_mode 0x00
saveenv
reset
Note:
The default value is RS232.
Cp210x support four port, but RSB4710 Only ttyUSB2 and ttyUSB3 support RS485
mode.
Above command "setenv uart_mode 0x0c", 0x0c means set bit2(ttyUSB2) and
bit3(ttyUSB3) to 1 (0 means to RS232; 1 means to RS485).
If you just want ttyUSB2 (or ttyUSB3) to be RSB485 mode, please change 0x0c to
0x04 (or 0x08).
EPC-R4710 User Manual
Device Node
/dev/ttyS4
/dev/ttyS2
/dev/ttyUSB0
/dev/ttyUSB1
/dev/ttyUSB2
/dev/ttyUSB3
22
Remark
Support RS232, no flow control
Debug Port
Support RS232
Support RS232
Support RS232 and RS485
Support RS232 and RS485
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