USB On-The-Go

Back in the day when cameras still took better photos than phones, I've always wanted to backup vacation photos without bringing a computer.

I still remember getting so close with the Google Nexus 4 to being able to connect an SD card reader. It supported OTG, but did not have the required charge pump to supply 5V of VBUS. (Supposedly you could hack together something using a 9V battery, some resistors, and a kernel patch, but that was a bit more than I was willing to risk for the convenience.)

Finally, the Nexus 7 and Nexus 5 supported it out of the box, and while Android didn't offer a FAT32 implementation back then, there was (is?) a USB host API which let apps supply that instead, and I think somebody actually ended up implementing FAT32 in userspace to make it all work!

I went on a long trip with a mirrorless camera and a SanDisk 500GB portable disk. My "computer-less" backup solution was a Pi-esque machine with USB3 (a RockPi), a powerbank, a card reader, and connecting my phone over USB and tethering it. This gave the RockPi an IP I could ssh into, and I'd ssh from the phone and ran rsync to copy the images from the SD card in the reader to the SanDisk portable drive.

I should make a custom Linux image for the Pi4+ (the whole process is probably too slow without USB3) and some automation (Jenkins?) to do this, I'm sure there's photographers who'd find it useful.