I have a smart card-like miniSD card (it's a javacard as far as I know) and I'm trying to write an emulator for it that runs on Windows and Linux. The emulator will be used in software integration tests. I want to test my client without using the actual hardware for several reasons. One reason is that the actual hardware will change its state irreversibly and doesn't allow a complete reset.
The device implements a mass storage with FAT32 file system. It contains a special device file that is being used for controlling the device via simple file write/read operations.
My goal is that the virtual (emulated) device appears with drive letter in Windows explorer as soon as the emulator is started, similar as if someone would actually plug a real device.
I wonder if there is any open software project that I can base my program on? The biggest challenges are obviously
- Providing/developing a "virtual" (USB/SD) mass storage device
- Intercepting file I/O operations on the special device file.
According to Wikipedia, device files are a common way to simplify driver development. So I wondered if there are existing emulation solutions for driver developers. At least I couldn't find any.
Simulating the device file itself would be an important first step. My first idea was to use a normal file and to communicate with the client by actually reading/writing to this file while observing it. I.e. clear the file as soon as the client wrote to it and write the response into it. I don't know if this could work at all. One problem is that the client doesn't open the file with shared mode, so my simulator cannot access it at the same time.
Then I found out that QEMU can emulate mass storage, however it seems that it only supports image files and that probably doesn't allow device file.
Microsoft has some documentation about how to write USB device emulators and drivers but it seems to be very complex and I wondered if there is an exisiting solution that could be extended:
Finally there is the USB/IP Project, but I don't know if it is helpful as I still need to develop a driver and then I'm back at the complex MS documentation above.