Difference between revisions of "How to use UART RK3568"
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== ROM-5880 Borad == | == ROM-5880 Borad == | ||
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| COM2 | | COM2 | ||
| − | | /dev/ | + | | /dev/ttyS5 |
| RS232 2-wire | | RS232 2-wire | ||
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| COM4 | | COM4 | ||
| − | | /dev/ | + | | /dev/ttyS7 |
| RS232 2-wire | | RS232 2-wire | ||
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Revision as of 07:10, 11 April 2024
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
RSB-4810 Borad
| COM Name | Device Node | Remark |
| COM1 | /dev/ttyS4 | RS232 2-wire |
| COM2 | /dev/ttyS7 | RS232 2-wire |
| COM3 | /dev/ttyUSB2 | RS232 4-wire and RS485 |
| COM4 | /dev/ttyUSB3 | RS232 4-wire and RS485 |
| COM5 | /dev/ttyUSB0 | RS232 4-wire |
| COM6 | /dev/ttyUSB1 | RS232 4-wire |
Note :
KEDGE-350 Borad
Main Board
| COM Name | Device Node | Remark |
| COM0 | /dev/ttyS3 | RS232 2-wire and RS485 |
| COM1 | /dev/ttyS4 | RS232 2-wire and RS485 |
| COM2(UIO) | /dev/ttyS7 | RS232 2-wire |
| COM3(UIO) | /dev/ttyS8 | RS232 2-wire |
Note :
1. Only COM0 and COM1 support RS485 mode.
UIO-4031
| COM Name | Device Node | Remark |
| COM0 | /dev/ttyUSB2 | RS485 |
| COM1 | /dev/ttyUSB3 | RS485 |
| COM2 | /dev/ttyUSB0 | RS485 |
| COM3 | /dev/ttyUSB1 | RS485 |
| COM4 | /dev/ttyS7 | RS232 2-wire |
| COM5 | /dev/ttyS8 | RS232 2-wire |
ROM-5880 Borad
| COM Name | Device Node | Remark |
| COM1 | /dev/ttyS3 | RS232 4-wire |
| COM2 | /dev/ttyS5 | RS232 2-wire |
| COM3 | /dev/ttyS4 | RS232 4-wire |
| COM4 | /dev/ttyS7 | RS232 2-wire |
Note :
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 coming from cpu
RS485 Mode（Taking Kedge-350 for example）:
setenv uart_mode_cpu 3:1,4:1 saveenv reset
RS232 Mode（Taking Kedge-350 for example）:
setenv setenv uart_mode_cpu 3:0,4:0 saveenv reset
Note :
The default value is RS232.
Above command "uart_mode_cpu 3:1,4:1", 3:1 means set ttyS3 to RS485(0 means to RS232; 1 means to RS485).
If you just want ttyS3(or ttyS4)to be RS485 mode, please change "3:1,4:1"to "3:1,4:0"(or "3:0,4:1").
Config Uart coming from cp2108
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).