Transparently connect two devices via USB storage for one-way file exchange

### Context I want to go paperless with a document scanner which I can operate without having to turn on my PC or use an app on my smartphone. Additionally, I want the scanned documents to end up in my paperless-ngx installation where they will be processed and included in my document backups. I've read multiple posts and watched videos of how to go paperless and they usually recommend document scanners with duplex ADF and network capabilities to scan directly into SMB shares. Based on my research, devices such as the Brother ADS-1700W/ADS-1800W or Fujitsu/Ricoh ScanSnap iX1600 support this. My planned budget for a scanner was below the price point of those scanners and I'm too impatient to wait for a good used or refurbished deal, so I was looking for workarounds. I was wondering whether I can use some kind of bridge/adapter/connector to achieve the same setup with a simpler scanner such as the ScanSnap iX1300 that can only scan directly to a USB attached device. I want to exclude the cloud capabilities of the iX1300 for now and look for a solution that works for even simpler scanners. ## Question Is it possible to use a document scanner that stores the documents on a USB mass storage device *and* those documents become available to another device? The scanner would write files to the USB attached device and those files end up in my home server for paperless-ngx and backups. ### Ideas I though about the following possible angles, but could not find enough information to test or implement a solution. Since the storage is only written from the scanner, it could be attached writable to the scanner and read-only to my home server without causing problems with file integrity. I found through a comment on an StackExchange question () the [SanDisk 32GB Connect Wireless Stick Flash Drive](https://www.amazon.com/dp/B00ZCFYT5K) as a Wi-Fi-enabled USB stick. The stick seems to be discontinued though. Another product I found - the [My Passport Wireless Pro](https://www.westerndigital.com/en-ap/products/portable-drives/wd-my-passport-wireless-pro-hdd) - turns off the Wifi connection when attached via USB (from the user manual: "While connected to a computer, the drive's Wi-Fi is turned off."). It seems like I could possible simulate something similar via "Multifunction Composite Gadget" using USB OTG ()? That leads me to the idea of a dummy USB storage device where files are not stored directly on the stick, but only passed through to a network folder (SMB/CIFS/FTP/NFS/...). This seemed like a product which could be used in all kinds of contexts, but I wasn't able to find anything on it. I wouldn't mind using an additional device (e.g., RPi) and some syncing mechanism between the USB storage and a network folder, if that makes the setup possible.