Difference between revisions of "How to use UART for RK3399 RSB4710"
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| USB2COM3<br/> | | USB2COM3<br/> | ||
| − | | dev/ttyUSB3<br/> | + | | /dev/ttyUSB3<br/> |
| support RS232 and RS485<br/> | | support RS232 and RS485<br/> | ||
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3. COM2 is designed as debug port default. | 3. COM2 is designed as debug port default. | ||
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= How to config RS232 or RS485 mode = | = How to config RS232 or RS485 mode = | ||
Revision as of 02:54, 11 March 2020
Contents
Overview
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
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.
Boards
RSB4710 Borad
| COM Name | Device Node | Remark |
| COM0 | /dev/ttyS0 |
for BT Data |
| COM2 |
/dev/ttyS2 |
Debug Port |
| COM4 |
/dev/ttyS4 |
support RS232, no flow control |
| USB2COM0 |
/dev/ttyUSB0 |
support RS232 |
| USB2COM1 | /dev/ttyUSB1 |
support RS232 |
| USB2COM2 |
/dev/ttyUSB2 | support RS232 and RS485 |
| USB2COM3 |
/dev/ttyUSB3 |
support RS232 and RS485 |
Note :
1. Only COM4、USB2COM0、USB2COM1、USB2COM2、USB2COM3 are designed for custom using.
2. Only USB2COM2 and USB2COM3 support RSB485.
3. COM2 is designed as debug port default.
How to config RS232 or RS485 mode
Enter U-boot interrupt mode
Connect device to debug port, and open debug console. See more : How_to_debug.
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 cammand to config UART mode.
Config Uart Mode
Only ttyUSB2 and ttyUSB3 support RS485 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).