Having trouble accessing linux console over UART

[jaux_al]

I built a Linux image for iMX8 board, which was flashed to the SD card via the following commands:

bunzip2 -dk -f core-image-minimal-imx8qxpmek.sdcard.bz2 
sudo dd if=core-image-minimal-imx8qxpmek.sdcard of=/dev/sdb bs=1M conv=fsync

But when I insert an SD card, and connect the microUSB to the debug port from the host machine, I don't really see anything coming up in a serial session.

I see 4 UART ports coming up so that's good, but I don't really see anything let alone a Linux console in a serial session in at least COM32 and ttyUSB0 on Linux

I checked the switches on the board and they're set to ON, ON, OFF, OFF for 1-4 bits as suggested in the manual.

[joanxie]

what version do you download to the board? did you download the images to the sd card successfully? how about using uuu tools to download images to the sd card?

[jaux_al]

Linux version? 4.14.98.

I was able to flash the image to the SD card. I didn't look much into if certain files exist in the SD card because I see a yocto-build image can be flashed directly without having to worry about setting up partitions and what not.

are you implying the issue is potentially with the flashing technique? 

Isn't eMMC is required for uuu? SD card wouldn't work?

Also, given there are 4 ports, which port corresponds to which core? I see there are two different cores i.e cortex A and M. Core A runs linux and M freeRTOS?

[joanxie]

sd card can work, where did you get  the minimal sdcard images? did you built it by yourself? I suggest that you can download the demo images to test first, you can download them from the link as below:

https://www.nxp.com/design/software/embedded-software/i-mx-software/embedded-linux-for-i-mx-applicat...

[jaux_al]

I tried using one of the demo images into a new SD card which worked, but the same image file that I am generating from Yocto doesn't.

I built the image myself, via Yocto. Do you see what could be a possible reason for the board to not boot up properly?

[joanxie]

I never tested minimal images, how about building fsl-image-validation-imx or fsl-image-qt5-validation-imx? I have tested them successfully