i already managed to boot from the eMMC once, so i know it should work.

my main goal is/was to boot from USB-Stick using the CM3+

I managed to do this using the CM3L module. Here are the steps i took:

  1. Flash SD/eMMC with Raspberry Pi OS
  2. Start the Raspberry Pi and open command line and type: echo program_usb_boot_mode=1 | sudo tee -a /boot/config.txt
  3. Check if OTP bit is set correctly with: vcgencmd otp_dump | grep 17: If output is 17:3020000a everything is ok, otherwise reboot and try again
  4. Now flash an empty USB-Stick with Raspberry Pi OS and add the line Program_usb_boot_mode=1 To the config.txt file
  5. Don’t forget to delete the files on the eMMC or remove the SD-card
  6. Connect the USB_OTGID Pin to GND (If you removed the R12 Resistor)
  7. Plug in the USB-Stick and connect a micro-USB cable with enough Ampere to POWER IN

Now i removed the R12 from my IO Board and the OTP bit is set using the CM3L (i dont know if that only counts now for the CM3L or both)

Then i tried to flash the eMMC to recreate the steps using the CM3+ i took with the CM3L.

The problem i'm having is that it just wont boot anymore from the eMMC. I flashed it using balenaEtcher or Raspberry Pi Imager and it finished without Errors. Then when i connect it to power, my screen with hdmi gets no signal. Just the ACT and PWR LED flashing.

Does anyone have a suggestion? Any help is appreciated.

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