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:
- Flash SD/eMMC with Raspberry Pi OS
- Start the Raspberry Pi and open command line and type: echo program_usb_boot_mode=1 | sudo tee -a /boot/config.txt
- 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
- Now flash an empty USB-Stick with Raspberry Pi OS and add the line Program_usb_boot_mode=1 To the config.txt file
- Don’t forget to delete the files on the eMMC or remove the SD-card
- Connect the USB_OTGID Pin to GND (If you removed the R12 Resistor)
- 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.