Difference between revisions of "How to use UART RK3568"
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| '''Remark''' | | '''Remark''' | ||
|- | |- | ||
| − | | | + | | COM1<br/> |
| /dev/ttyS4<br/> | | /dev/ttyS4<br/> | ||
| support RS232, no flow control<br/> | | support RS232, no flow control<br/> | ||
|- | |- | ||
| − | | | + | | COM2<br/> |
| /dev/ttyS7<br/> | | /dev/ttyS7<br/> | ||
| support RS232, no flow control<br/> | | support RS232, no flow control<br/> | ||
| − | |||
| − | |||
| − | |||
| − | |||
|- | |- | ||
| COM3<br/> | | COM3<br/> | ||
| − | | /dev/ | + | | /dev/ttyUSB2<br/> |
| − | | support RS232<br/> | + | | support RS232 and RS485<br/> |
|- | |- | ||
| COM4 | | COM4 | ||
| − | | /dev/ | + | | /dev/ttyUSB3<br/> |
| − | | support RS232<br/> | + | | support RS232 and RS485<br/> |
|- | |- | ||
| COM5<br/> | | COM5<br/> | ||
| − | | /dev/ | + | | /dev/ttyUSB0 |
| − | | support RS232 | + | | support RS232 |
|- | |- | ||
| COM6<br/> | | COM6<br/> | ||
| − | | /dev/ | + | | /dev/ttyUSB1<br/> |
| − | | support RS232 | + | | support RS232<br/> |
|} | |} | ||
Revision as of 06:59, 29 November 2021
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
RSB4810 Borad
| COM Name | Device Node | Remark |
| COM1 |
/dev/ttyS4 |
support RS232, no flow control |
| COM2 |
/dev/ttyS7 |
support RS232, no flow control |
| COM3 |
/dev/ttyUSB2 |
support RS232 and RS485 |
| COM4 | /dev/ttyUSB3 |
support RS232 and RS485 |
| COM5 |
/dev/ttyUSB0 | support RS232 |
| COM6 |
/dev/ttyUSB1 |
support RS232 |
Note :
1. Only USB2COM2 and USB2COM3 support RSB485.
2. 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 RSB4810 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 RS485 mode, please change 0x0c to 0x04 (or 0x08).