Verdin imx95 Preempt RT + HW questions

Technical Support
1

I recently acquired an imx95 dev kit and the Dahlia carrier board. I was able to flash it with the Torizon OS 7.4 Easy Pair image with easy installer no problem. It boots and I’m able to log in to it over ssh. However, I’m running into a couple of problems…

  1. For my use case, I will require a kernel with the preempt rt patch set applied. I’ve tried a few different version of Torizon OS 7.5 with PREEMPT_RT from easy installer (after enabling the extra feed) and none of them boot. The default Torizon OS 7.4 Easy Pair works fine. I know the PREEMPT_RT images have the caveat of incomplete testing but I would expect them to boot if the smoke tests pass. Is there a specific PREEMPT_RT build that is confirmed to boot?

  2. I am unable to get any serial debugging output. I have the usb-c connected to my computer, but only two COM ports show up in device manager (docs say that 4 should appear?). Using Putty with the recommended settings, there is no output or loopback. I’ve tried both of the COM ports. Is this expected?

2

Hi, I’m the Toradex AI Assistant.

I might make mistakes or occasionally get you wrong. Our support team will step in if needed.

I can help you with both issues you’re experiencing with your iMX95 dev kit and Dahlia carrier board setup.

Serial Debugging Setup

Regarding your serial debugging issue, the Dahlia Carrier Board should provide 4 serial ports when connected via USB-C to the DEBUG connector (1). The documentation indicates that “Verdin has an integrated Serial-to-USB converter that lists 4 serial ports on your computer. The highest index is the Linux serial console. Example, if you see /dev/ttyUSB0, /dev/ttyUSB1, /dev/ttyUSB2 and /dev/ttyUSB3 listed, then /dev/ttyUSB3 is the serial console. The same logic applies to Windows COM ports” (1).

Since you’re only seeing 2 COM ports instead of the expected 4, there may be a driver or connection issue. The documentation also warns that “If you connect to the first or the second port (for example /dev/ttyUSB0 or /dev/ttyUSB1), you will not be able to use the board. This happens because those ports are dedicated to power/reset control and FTDI JTAG. Just close those connections and reset the board” (1).

For your setup:

  • Ensure you’re connecting the USB-C cable to the correct DEBUG connector on the Dahlia board (1)
  • The highest-numbered COM port should be your Linux serial console
  • Try using standard serial terminal settings as referenced in the documentation (1)

PREEMPT_RT Image Issues

Regarding the PREEMPT_RT kernel images not booting, this appears to be a known limitation. As you mentioned, these images have incomplete testing coverage. Unfortunately, the available documentation doesn’t specify which particular PREEMPT_RT builds are confirmed to work with the iMX95 platform.

Hardware Platform Information

To better assist you with platform-specific guidance, could you run the tdx-info command on your working Torizon OS 7.4 installation? This will provide detailed information about your exact hardware configuration. You can find more information about this command at: Getting Device Information with Tdx-Info | Toradex Developer Center

This information will help identify any specific considerations for your iMX95 dev kit setup and potentially provide more targeted guidance for both the serial debugging and PREEMPT_RT kernel issues.

Best regards,
Toradex AI Assistant.

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3

With regard to the serial debugging port, I am connecting to the USB-C port that has “Debug” marked on the silkscreen. It does enumerate as two serial ports… so it’s odd that all four don’t show up.

Here’s the output of tdx-info

Software summary
------------------------------------------------------------
Bootloader:               U-Boot
Kernel version:           6.6.101-7.4.0-g557af2783d91 #1-Torizon SMP PREEMPT Thu Sep 25 07:49:28 UTC 2025
Kernel command line:      root=LABEL=otaroot rootfstype=ext4 quiet logo.nologo vt.global_cursor_default=0 plymouth.ignore-serial-consoles splash fbcon=map:3 ostree=/ostree/boot.1/torizon/6f0b7f5229fbaebd246cb1b3fc5579563411a1e41f77e57423b7ece8209a4dc9/0
Distro name:              NAME="Torizon OS"
Distro version:           VERSION_ID=7.4.0-build.28
Distro variant:           VARIANT="Docker"
Hostname:                 verdin-imx95-12594096
------------------------------------------------------------

Hardware info
------------------------------------------------------------
HW model:                 Toradex Verdin iMX95 WB on Verdin Development Board
Toradex version:          0089 V1.0A
Serial number:            12594096
Processor arch:           aarch64
------------------------------------------------------------
4

Thank you for providing the tdx-info output! I can see you’re running Torizon OS 7.4.0 on a Verdin iMX95 with the Verdin Development Board, not the Dahlia carrier board as initially mentioned.

Serial Debug Port Issue

Based on your tdx-info output, you’re using the Verdin Development Board rather than the Dahlia Carrier Board. This explains the discrepancy in serial port behavior. According to the documentation, for the Verdin Development Board, you should connect a USB-C to USB Type-A cable to X66 (1).

The documentation states that “Verdin has an integrated Serial-to-USB converter that lists 4 serial ports on your computer. The highest index is the Linux serial console. Example, if you see /dev/ttyUSB0, /dev/ttyUSB1, /dev/ttyUSB2 and /dev/ttyUSB3 listed, then /dev/ttyUSB3 is the serial console. The same logic applies to Windows COM ports” (1).

However, since you’re only seeing 2 COM ports instead of 4, this could indicate:

  • A driver issue with the USB-to-serial converter
  • The specific iMX95 implementation may have different serial port enumeration
  • Hardware-specific behavior for the iMX95 platform

For troubleshooting:

  1. Ensure you’re using the correct USB-C connector (X66 on the Verdin Development Board) (1)
  2. Try the highest-numbered COM port that appears for console access
  3. Use the standard serial parameters: Baud Rate 115200, Parity none, Bits 8, Stop bits 1, Flow control none (1)

PREEMPT_RT Kernel Issue

Regarding the PREEMPT_RT kernel images not booting on your iMX95, this appears to be a platform-specific issue. The documentation doesn’t specify which PREEMPT_RT builds are confirmed to work with the iMX95 platform, and as you noted, these images have incomplete testing coverage.

Since this is a newer platform (iMX95) with specific requirements, the PREEMPT_RT support may still be in development or require specific configuration adjustments.

Best regards,
Toradex AI Assistant.

Did you like my answer? :+1: :-1:

If I answered your question, please tick the “Solution” checkbox.

For follow-up questions to me, please use @ToradexAI in your post.

5

I figured out the serial port confusion. This page: Serial/UART - Target Device Setup | Toradex Developer Center says that the dahlia board will enumerate as four COM ports, however on windows only two enumerate. That page also says to use the highest numbered com port - but this is wrong, it should be the lower numbered com port.

After using the correct COM port, I am able to see the expected output (U-boot and then the serial console) with the Torizon OS Easy Pair release (non RT).

However, after flashing any of the preempt-rt images with easy installer, there is zero output on that same serial console. No U-boot, nothing. When easy installer was running, I checked the tezi.log file to verify that the image was flashed without any issues. Any ideas?

6

Hey @PJohnson,

Thanks for the further investigation to show that the non-rt works as expected. It’s odd that there isn’t any output on the debug console. I don’t have a imx95 currently to test, but I will bring this back to the team to see if anyone can/has tested.

-Eric

7

hey @PJohnson,

Can you verify which RT patch version you have downloaded in comparison to which version imx95 you have? There are some version requirements between Silicon A1 and Silicon B0 that forces different versions. And this isn’t apparent on Tezi.

Verdin IMX95 Silicon V1.0A -A1 → 7.4.0
Verdin IMX95 Silicon V1.0B - B0 –> 7.5.0

8

Much appreciated! That makes sense. I hadn’t found that page before, but I did track down the latest 7.4.0-rt monthly release and that booted fine.