I want to format my external SD card (For installing Raspbian) and I don't have a SD card reader on my PC or an external one. Is there a way to use my Android phone as a SD card reader?
PC OS: Windows 7
Phone: Rooted Note 3 (N9005)
I believe there is. I use Nexus Media Importer (though I think it works on most phones with OTG) and it works as a basic file explorer.
There is a free version, but I can't remember what the limitations are. (I have a feeling it might just be pictures.)
DriveDroid is a powerful utility than enables you to create a virtual USB image on your phone, and when you connect it to the PC, it recognizes the USB image, as if it's a real USB plugged. I used this utility to install both Windows and Linux to my systems, and I think it should work as live USB, too.
Sorry I never use any note 3 myself and not sure if this device has external SD card attaching option.
But for almost all android I did have or may operate somehow has standard USB storage device built-in. Anyone connect any Android operated phone with Windows 7 PC over USB windows automatically detects as standard storage of USB type device. Some of phone might ask use about which mode they want to present their device to windows 7 PC as soon USB cable plug-in followed by list of available options. Comin options are MTP , USB storage device, charging only, CD Rom external. In case of CD rom mode choice was maid luckily CD rom having drivers file might appear on Windows. Such way connecting USB cable flowed by choosing USB storage will configures your Android phone as USB devices mean your required USB card reader will ready for you.
Removing any existing drivers of Android including all MTP devices will allow Windows 7 to reinstall required drivers if you have problem detecting phone while plug-in with USB.