CuteCom shows repeating characters when reading uart

[basprins]

Hi, I am having this issue for a long time now, and tried several times to figure out what goes wrong. Before I continue, I don't have the impression that this is an issue with CuteCom at all, I was just hoping that you might now more (assuming you have far more experience with ubuntu/serial/uart than I do).

So, since "a version" of ubuntu (currently I'm on 23.04) I started noticing some repetitive characters when reading from the uart of my micro controller. At first I though I caused a serious bug on my side in the MCU, but after monitoring the stream of bytes using a logic analyzer, I found that the micro controller sends the data just fine. But somewhere on the host side (my ubuntu development pc) the data gets corrupted by repeating a char N times completely at random.

I can't find any way to get a better handle on this. I played around with flow control in CuteCom to see if that solves the problem, but it doesn't.

I am connecting to ttyACM0 if that makes a difference. So it's not an actual ttyUSB device. I know ACM has something to do with an old school driver used for modems. The "other side" is my JLink programmer, where one wire of the JLink is directly connected to the uart TX on the microcontroller. Again, using the logic analyzer on that pin on the JLink gives perfect communication. So from JLink to my USB connector and through the ubuntu kernel to CuteCom something goes wrong. I have no idea where to start.

Do you by any chance recognize this problem?

Are there solutions / workaround you could suggest?

Can I e.g. force ttyUSB drivers so that the device is not recognized as ttyACM0 but as ttyUSB0, and if that would be possible, would I have a chance of solving the problem?