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I have a problem with my pl2303 converter. I'm using two of them like this:

LAPTOP <-USB-SERIAL-> <-SERIAL-SERIAL-> <-SERIAL-USB-> RASPBERRYPI

In other words, I'm connecting Raspberry Pi with my laptop using two usb-to-serial converters and having null modem in the middle.

I can communicate through minicom and "visually" it looks fine (all information is sent properly), but when I look into the logs it produces following dmesg output:

[  343.390610] pl2303 ttyUSB1: pl2303_get_line_request - failed: -32
[  343.685367] pl2303 ttyUSB1: error sending break = -32

I could live with that as long as everything works fine... but it doesn't. For example, I can't connect with RPi via ser2net. The "other side" simply doesn't get the messages. I suspect that this error is the cause of this problem. I was googling around, but I didn't find any solution. Could somebody help me with it?

Also - when I try to connect via ser2net, one thing breaks. Before that I can to stuff like

cat -v < /dev/ttyUSB0

and

echo "blablabla" > /dev/ttyUSB0

with success. After I try to connect via ser2net, it stops working and only minicom communication is fine.

Krzysztof Buczak
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1 Answers1

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This is a late answer but maybe someone can use it.

TLDR: Replace PL2303 USB to serial with FTDI FT232.

Had the same problem with my Pi monitoring my solar controller. Got the same two errors every 10 seconds when i started scanning data. I use pymodbus for communication.

Changing PL2303 to FTDI FT232 have solved the problem.

I guessed it is a timeout in the PL2303 driver. I open the serial connection once, and keeps it open forever.

To test, I tried changing my code to open the connection before scan and close the connection again afterwards. This did not change anything, except my program survives unplugging and replugging the USB.

Per
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