Astin said:
Actually interesting idea.
Technically speaking it is possible. But you would need a thumb drive that can communicate with your camera, or a microcontroller chip inside the thumb drive. Currently all the thumb drives in the market are "dumb" devices, there is no microcontroller inside. If someone have the time, build a circuit board for the microcontroller, write a simple program to communicate (send/receive), your idea is possible.
Economically speaking it is not a good idea, because a thumb drive is more expensive than a memory card.
Need to correct you on some mis-conceptions.
USB interface is a top-down, host-device type of relationship. On any system, there is a only 1 host (ususally the PC) and multiple devices. All communications are between the host and any particular device at any time and the communications are only initiated by the host. Thumb drives and digicams are devices, so you cannot connect them to each other and expect them to communicate without a host controller.
USB devices are not "dumb". They all have micro-controllers, just that the micro-controllers function as USB devices instead of a host controller. In fact it is very rare to find any piece of electronic equipment without a microcontroller nowadays.
To have a digicam talk to a thumb drive directly, a USB host controller has to be build into the camera. This is theoretically probably possible but I am not sure how the camera should react if a USB device that is not a storage device is plugged into the camera. Maytbe it is possible to have a USB host controller that can only recognise and work with storage devices and reject all other kinds of devices.
It is also theorectically possible to design a mass storage device that has a host controller built in. In that case it will treat the camera as a downstream device. The problem is that it would have to be able to switch its functionality between a host and a device. When connected to an exisiting camera to download the pictures, it has to function as a host. When connected to the PC, it has to function as a device. As a host, it has to supply power to downstream devices, and never take power from downstream devices. As such, such a device cannot be in a thumb-drive format, but more like a X-drive kind of device.
One more possibility is to build a portable USB host such that the camera and the thumbdrive can be connected to this host and the host can control the transfer of files fromt he digicam to the thumbdrive. I believe there is such a product available now.
In any case the microcontroller programming will be far from simple.
- Roy
