Omromis
Posts: 1
Joined: Wed Jul 04, 2018 11:31 am

Booting CM3 from memory stick

Wed Jul 04, 2018 11:40 am

Hello. Is it possible to run compute module 3 from memory stick as from SD card? I uploaded a raspbian image using an etcher and put the pendrive into the USB HOST connector on the IO Board V3.0. Is this situation possible at all? What do I have to make it work?

W. H. Heydt
Posts: 9207
Joined: Fri Mar 09, 2012 7:36 pm
Location: Vallejo, CA (US)

Re: Booting CM3 from memory stick

Thu Jul 05, 2018 5:31 am

Maybe...but it will try to boot from the on-board flash module first. If you really want to boot from an external device, look at the CM3L.

gsh
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 1347
Joined: Sat Sep 10, 2011 11:43 am

Re: Booting CM3 from memory stick

Thu Jul 05, 2018 11:00 am

Yes this is possible, but there are a couple of things you need to do, first off you need to set the program_usb_boot_mode=1 bit in the otp (just add to config.txt and boot...) you should be able to do this over the USB device boot, using usbbootgui on a Raspberry Pi or our x86 release. You can just select 'custom application' and point it at a directory that contains bootcode.bin, start.elf and config.txt and it should correctly program the bit.

Then you need to make sure the otg_id pin is correctly pulled to enable host mode (i.e. drive to ground), noting that if you enable host boot mode then the otg_id is used to select between device mode and host mode (it needs to be a host to boot from mass storage). By default the OTG_ID pin has R12 which pulls it to ground for you, so I would suggest you remove this resistor and then use a jumper to switch it to host mode...

To make it then return to device boot mode you'll need to let the OTG_ID pin float (i.e. R12 will need to be removed to make it programmable after having set the usb_boot_mode bit...
--
Gordon Hollingworth PhD
Raspberry Pi - Director of Software Engineering

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