Ah WTF. All I'm trying is to connect a CD-ROM drive to a RPi 400, but somehow mtp-probe keeps rescanning the device as soon as a medium is inserted, making it completely unusable.

Uuuugh... Somehow, USB devices are an unmitigated desaster in RPi OS... I've already lost my USB boot device when connecting another USB storage gadget, but USB Wifi (which I use instead of the abysmal internal Wifi module on the RPi 400) getting disconnected when a disk is loaded into a USB CDROM is a new low...

@galaxis hmmmm power issue? I cannot make my USB CDROM work properly with the PI unless i feed external power via a Y-Cable.

@emanuel Hrm, didn't see any warnings to that end, but not impossible? Though it really shouldn't be an issue on one of the USB3 ports of an RPi 400...

@galaxis i am not too sure either if its related. Just wanted to mention it - i ran into similar problems on a Rpi4 (KODI setup) with USB (hi-gain) WIFI + USB-DVDROM.

@emanuel @galaxis yeah, it sorta _feels_ like a not-quite-enough-power scenario.

@brennen @emanuel Frustratingly, it does seem to be a power issue after all: Even though the USB DVD drive is nominally rated for just 500mA, it doesn't spin up with a CD inserted on one of the USB3 ports of the RPi 400. It does read the CD as soon as I disconnect the USB2 hub with Wifi and mouse from the USB2 port next to it. 🙄


@galaxis @brennen @Iutech yea, i have this time and time again with USB DVDROMs, especially hooked up to PI or other low-power devices. I heard a 3A / 5V power adapter on a Pi4 can help, but when i build such setups, i just supply additional power using a Y-Cable.

@emanuel Funny enough, when I boot the system from an SD card instead of using the USB3 flash stick, I can use the DVD drive just fine too. So it seems to be just about within the margin of powerable devices, but two more small consumers stretch the budget too much on the RPi 400. The official USB-C power supply is rated for 15W, which should really be enough in principle?

@brennen @Iutech


RPi OS or material defect due to all sharing the same bus ?

@Iutech That's not true for the RPi 400: The USB ports are provided by a dedicated 4-port controller on the PCIe bus of the SOC.
I'll have a closer look at what's actually going wrong as soon as I find some more time.

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