Custom BBB eMMC boot issue

Hello everyone,

We are currently bringing up a custom BBB. The goal is to flash a custom image into the eMMC, using BBBlfs. It works fine on an official BBB we used for months, but gets stuck at the ROM code on our custom BBB.

Here are the status of the investigations:

  • With the eMMC erased, the board prints CCCCC characters on the serial console.
  • We can flash the custom BBB eMMC using BBBlfs, seeing BBBlfs uboot and Linux trace.
  • With the eMMC flashed with our image, the board does not print any C characters on the serial console, it does not even print MLO header.
  • Once the eMMC is flashed, we can write some files into it, and the files flashed are correct (same md5sum), even after a reboot.
  • The eMMC clock is active and working when some file are written on the eMMC
  • Flashing the official image does not works either.

The image we flash uses a FAT32 boot partition with the boot flag activated. As stated before, this image boots without any issue on an official BBB. We also tried RAW mode following this post, but it does not work either.

The image uses u-boot 2022.04, and the boot partition contains MLO, u-boot.img and uEnv.txt.

One difference with the official BBB is that the custom one has a blank EEPROM, and thus the uboot used to flash with BBBlfs was modified to manually fill the EEPROM header used in the SPL to check the board name and revision. Using this modified uboot works on an offical BBB.

We are now comparing the eMMC signals (CLK, DAT0, CMD) between the official and the custom BBB but we are running a bit out of idea on how to proceed with the next investigations.

It is to note that our custom BBB does not have an SDcard reader, but I can solder one if needed.

Does it rings a bell to someone having done this kind of stuff in the past? Don’t hesitate to tell me for any additional info needed!

Best regards


It actually was the U-Boot which was flashed into the eMMC that was not patched correctly to manually fill the EEPROM readings. It now boots correctly on our custom BBB!