ttyUSB0 Configuration and BaudRate keep changing on Its Own


Toradex BSP 6.5 & 6.6
Linux kernel 5.15
Iris 2.0 Carrier board

USB Serial Connected to USB Type A on Iris Carrier Board

I have installed a QT Serial App using the Toradex reference Multimedia image with BSP versions 6.5. but the serialPort function isn’t working correctly.

Every time I set the ttyUSB0 baud rate and configuration, it changes spontaneously for no apparent reason.

After installing the Toradex reference Multimedia 6.6 from the cloud onto the machine without any modification, I open the Wayland Terminal and input stty -F /dev/ttyUSB0 -a. Each time, it shows a different baud rate, and I have noticed a pattern.
the Baudrate cycles between 4800 - 921600 and it changes about every 2s.

Is this a Bug or function? how can I fix this issue.


We have never encountered or received reports of such an issue before. It is most likely related to the QT Serial App you mentioned. Could you please check if this issue is reproducible when the QT Serial App is not running? Could you please also specify which exactly USB-to-Serial adapter you are using? Have you tried a different one?

Hi Alex,

This happens even when I use the Reference Multimedia image from Easy Installer Network Image(Your official image) without any modification or my application.

The issue is reproducible with different Iris Carrier board and different Colibri-IMX8X Module (Both Toradex BSP 6.5 & 6.6)

However, this issue does not happen on Boot2QT 6.5.3 Image with the same hardware. I don’t know which toradex BSP Version does Boot2QT 6.5.3 use. (All the same hardware and Same USB-to-Serial Adapter)

The USB-to-Serial Adapter is ** Tripp Lite USB-A to RJ45 Serial Rollover Cable (Model Number: U209-006-RJ45-X)*
Different USB-to-Serial Adapter(Same Brand) also gives the same outcome. I don’t have a different brand Adapter to try yet.


Unfortunately I wasn’t able to reproduce the issue you reported.
Repro steps:

  • Colibri iMX8X module flashed with the TDX Wayland with XWayland 6.6.0+build.12 (kirkstone) colibri-imx8x-06846836 -Colibri-iMX8X_Reference-Minimal-Image
  • Future Technology Devices International, Ltd FT232 Serial (UART) IC based adapter

idVendor 0x0403 Future Technology Devices International, Ltd
idProduct 0x6001 FT232 Serial (UART) IC
bcdDevice 6.00
iManufacturer 1 FTDI
iProduct 2 FT232R USB UART
iSerial 3 B000Y4CU

  • Set its speed using stty -F /dev/ttyUSB0 115200 command
  • Connect the USB to serial adapter to my PC
  • run Tera Term program on my PC to check communication. Set related com port speed to 115200
  • use echo “sometext” >/dev/ttyUSB command on Colibri and check if the text is received by TeraTerm
  • run the above command many times.
    Results: each time correct text was received
  • run stty -F /dev/ttyUSB0 command on Colibri a few times
    Results : speed 115200 baud; was always reported.

Hi Alex,

I tested the same image you used :Colibri iMX8X module flashed with the TDX Wayland with XWayland 6.6.0+build.12 (kirkstone) colibri-imx8x-06846836 -Colibri-iMX8X_Reference-Minimal-Image

The Issue does not happen.

Thus this issue exist only with Toradex Reference-Multimedia-Image Which is what my Custom yocto build is based on. Can you test the Toradex Reference-Multimedia-Image on your hardware and see if the problem exists?


So After checking if any other process is accessing the serial port lsof | grep ttyUSB0

I can see gpsd 789 nobody 8u CHR 188,0 0t0 559 /dev/ttyUSB0 gpsd 789 875 gpsd nobody 8u CHR 188,0 0t0 559 /dev/ttyUSB0

Apparently gpsd is causing this weird behavior, Once i Stopped the gpsd systemctl stop gpsd The Baudrate no longer changes.

I’m going to Remove gpsd from my Yotco build and see if it’s good

Edit: I can confirm that after removing gpsd from Multimedia-Image have resolved this issue

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