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pishotta
Posts: 5
Joined: Mon Nov 21, 2016 12:50 pm
Location: St. Augustine, FL, USA

usb boot conundrum

Sun Feb 19, 2017 8:39 pm

Hi,

I followed instructions to get RPi-3 to boot from a USB stick (a SanDisk Ultra 64) under updated and upgraded Raspbian Jessie. It works just fine, just as described, but won't boot when I I have a USB Logitech webcam plugged in.

1. The webcam works OK if I plug it in after the boot
2. I added "rootdelay=10" to /boot/cmdline.txt
3. I used the UUID of the /root file system in fstab instead of the /dev/sda2 designation
4. It boots OK with keyboard, mouse, and other additional memory sticks in the USB sockets
5. Using a powered USB hub to connect the camera (if a power issue) didn't help
6. Juggling what's plugged into what USB slot doesn't help either
7. Neither dmesg, syslog, nor messages show anything obvious (it probably never gets that far)

But absolutely nothing happens on the screen when a webcam is plugged in (I tried two different ones). I get one flash of the activity light on the USB boot device, but nothing thereafter. Works perfectly without the camera plugged in. Seems like the camera is fouling up the hunt for a boot device.

I'm not exactly a beginner, but neither am I an experienced systems programmer. Have appealed extensively to God (aka: Google), but alas no answer. A puzzler, and I'm stumped. Any revelations?

-- Fred P.

epoch1970
Posts: 4746
Joined: Thu May 05, 2016 9:33 am
Location: Paris, France

Re: usb boot conundrum

Mon Feb 20, 2017 11:01 am

Perhaps your rootwait comes in too late to be useful.
Do you have program_usb_timeout=1 in config.txt?
https://github.com/raspberrypi/documentation/blob/master/hardware/raspberrypi/bootmodes/bootflow.md wrote:USB enumeration is a means of enabling power to the downstream devices on a hub, then waiting for the device to pull the D+ and D- lines to indicate if it is either USB 1 or USB 2. This can take time: on some devices it can take up to three seconds for a hard disk drive to spin up and start the enumeration process. Because this is the only way of detecting that the hardware is attached, we have to wait for a minimum amount of time (two seconds). If the device fails to respond after this maximum timeout, it is possible to increase the timeout to five seconds using program_usb_timeout=1 in config.txt.
HTH
"S'il n'y a pas de solution, c'est qu'il n'y a pas de problème." Les Shadoks, J. Rouxel

User avatar
pishotta
Posts: 5
Joined: Mon Nov 21, 2016 12:50 pm
Location: St. Augustine, FL, USA

Re: usb boot conundrum

Mon Feb 20, 2017 1:48 pm

Thanks. Good thought, but it didn't help. I think the firmware that supports this boot modality is still "experimental"? Perhaps I've bumped into something unanticipated. Odd that the problem only seems to happen with webcams plugged in. I've tried two different Logitech models -- same behavior. Nothing else I have seems to cause the problem. It does seem that boot device detection is somehow being defeated.

-- Fred P.

halfluck
Posts: 13
Joined: Mon Sep 24, 2012 2:27 am

Re: usb boot conundrum

Mon Nov 13, 2017 11:11 am

Hey Guys,

I'm having the exact same issue, RPI3 Booting USB and it wont do anything with the Logitech C270.
Have you made any progress?

Cheers Rob.

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