cannot receive data through RS232 serial port

Hello everyone,

I’m trying to use the RS232 serial port to connect the board with another computer,but I can only send data from the board, but not able to receive data from the computer.

is there any solution for this problem?

any info would be greatly appreciated!

It may be a flow control issue. It also depends on your cable. Check configuration on both ends are matching with your cable’s capability (if it has only 3 wires, then HW flow control is not possible).

I use 115200 8N1 with CTS/DTS CTS/RTS flow control. Try CTS/DTS CTS/RTS and also software flow control.

I have not observed a flow control issue on the TK1 nor the TX1, but if you were using a TX2 then there is an issue with flow control not working.

It’s really kind for you! Thank you!However,I use minicom both on the board and pc.And I set CTS/DTS flow control and software flow control,but it didn’t help.The problem still exists.

And now I am going to try the extended IO UART_1,should I consider flow control?

Have you tried another cable ? Null modem with all wires for HW (CTS/DTS CTS/RTS) flow control as expected by TK1 ?

[EDIT: as pointed out by @linuxdev, this copy/paste was propagating confusion (with DTR?)].

Correction: Earlier I used initials “CTS/DTS”, it’s actually “CTS/RTS” (instructions are still correct, but it stands for “Clear To Send” and “Request To Send”).

Keep in mind that the 9-pin D-sub connector has serial console bound to it, and I am assuming you want this for serial console. If you’ve mixed other use in with this you’d have to first disable serial console. However, I’m continuing on the the idea that you are intending serial console, the above settings should work.

If the serial connection settings at both sides of the wire do not match you could experience issues similar to what you have. The fact that you get data transfer in one direction says the 115200 8N1 is probably correct on both sides of the wire. My thoughts on flow control are because I use CTS/RTS where possible, and in fact I’ve used this with a couple of JTK1s successfully for a very long time using every L4T version. This is a form of hardware flow control and adds reliability up through much faster speeds than 115200…without this 115200 is probably the limit before starting to worry about quirks.

My thoughts on CTS/RTS versus software flow control are because I have experienced exactly the issue you have (on different hardware running L4T) when CTS/RTS was attempted, but had the problem go away under software flow control. Can you look at the 9-pin D-sub connector side and check if the pins are all in place and not bent or missing?