ECNapadilla
Posts: 2
Joined: Thu Jun 06, 2019 3:01 pm

CM3 4GB eMMC image backup

Thu Jun 06, 2019 3:23 pm

I have a CM3 inside an industrial gateway (Kunbus Revolution Pi), I have set the OTP bit "program_usb_boot_mode" and the RPIboot program in Windows doesn't work (stays in "Waiting for BCM2835/6/7").
The boot used to work before the OTP bit and now I can´t read/write the image to the CM3.
I hace seen in a forum that this is caused because the CM3 boots to Host mode all the time and not in Boot mode, so the only way to handle this was to remove SD or disable eMMC. I already disabled the eMMC successfully but still can't enter Boot mode.
I want to restore the CM3 to a backup image that I have because I filled all the storage but I can't manage to do that.

Any advice would be helpful.

gsh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 1416
Joined: Sat Sep 10, 2011 11:43 am

Re: CM3 4GB eMMC image backup

Thu Jun 06, 2019 3:57 pm

The USB device boot mode (i.e. booting using rpiboot) is enabled by default, by adding usb_host_boot_mode you've enabled host boot mode as well. To choose between them the bootrom looks at the value of the OTG_ID pin and if it is high will boot as a device (rpiboot), if it is low then it'll boot as host (mass storage or ethernet boot)

The OTG_ID pin has an internal pull up so I would assume your base board has this pulled either with a resistor or a link to ground. Remove this and it should work

Gordon
--
Gordon Hollingworth PhD
Raspberry Pi - Director of Software Engineering

ECNapadilla
Posts: 2
Joined: Thu Jun 06, 2019 3:01 pm

Re: CM3 4GB eMMC image backup

Thu Jun 06, 2019 6:20 pm

Where can I look for the OTG_ID pin link in the board itself to remove the element to ground. I have seen this recommendation before but it said something about GPIO 47 which is only for the CM1.
I would try to find the link.

Return to “Compute Module”