CM4 - OTG Mass Storage Help

[DrathianGull]

Hello,

I've been trying to set up OTG Mass Storage with access from the USB Slave, but when I plug it into my Windows 10 machine it comes up as a USB Serial Device instead.

I already enabled the USB by setting the overlay and mode in /boot/config.txt as

Code: Select all

dtoverlay=dwc2,dr_mode=peripheral

I also added dwc2 to the end of /etc/modules.

I also added this to the /boot/cmdline.txt

Code: Select all

fixrtc modules-load=dwc2,g_ether

Any help would be appreciated.

[PhilE]

What exactly are you trying to achieve? To use the CM4 storage as a USB MSD from Windows?

[DrathianGull]

We are trying to set it up so that a computer can just plug in and use it like a flashdrive for when the main program is not running

[PhilE]

The g_ether module is to create a network link between the guest and the CM4, so you probably don't need that.

Unfortunately Linux doesn't allow direct access to the main filling system in that way - imagine the problems that could arise if two hosts were trying to use the same EMMC device. Instead you have to run a special image on the CM4 that is downloaded by the usbboot/rpiboot utility, after which the CM4 behaves like an MSD until it is reset or power cycled.

[DrathianGull]

Understood. In that case I assume I can just create a separate partition and lock it in there that would just hold files and on startup the main partition could just grab the files before they can be accessed and make a copy of them inside if any changes had been made.

[PhilE]

You would need to use the mass storage gadget driver - there's a guide here (the first hit from Google): https://linuxlink.timesys.com/docs/wiki ... le_Storage

[incognitum]

Unfortunately Linux doesn't allow direct access to the main filling system in that way - imagine the problems that could arise if two hosts were trying to use the same EMMC device.

But indirect access to individual files do is possible. As in: do not focus too much on playing mass storage device, but consider speaking the MTP protocol mobile phones use to let you download your photos instead.

Need to run a daemon in userspace for that, like: https://github.com/viveris/uMTP-Responder