@Alexander Polko Do you still have stock firmware in eMMC? You should get some output from the serial uart if you have the stock firmware, otherwise your serial is not working correctly. Also, boot from sdcard only works via u-boot from stock firmware on this board, for the reason I stated above.

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I also tried different U-Boot SPL variants, but I was unable to get Armbian to boot. However, I noticed something interesting — on my MikroTik router I saw a DHCP lease that was issued to a client identified as "uboot", though I only noticed this after the fact and missed the chance to investigate further.

Hi @jock, thank you very much for your detailed explanation and for pointing me to the multitool project! I successfully built the multitool image for rk3528 and wrote it to the SD card, but unfortunately the box does not boot from it — it stuck every time. I also tried connecting via UART (FT232 adapter, 1500000 baud, 8N1) but I only get garbage/noise in the terminal — no readable output at all, even right after powering on the device.

@Nick A Thanks for taking my advice.😄 This is the test program of mine. You can play around with it if you have time. cpu_benchmark.py.zip