If I build a custom mbed without the magic chip can I still program it so that it would appear as a flash drive in windows? What I want to do is build a data logging device, I will likely use an external memory chip to store data and then connect the device to a pc where I can then access the data.

I was thinking of using txt files but if it requires less space and is easily implementable then I would write it as a binary file however I don't have any experience on the pc side as to how I would then 'decode' that data into something useful. Are there any sites/books someone could point me towards? Binary would be a more ideal solution as I may then expand it to send this wirelessly and then I wouldn't require the .txt file formatting.

Thanks :)

Its the magic chip which manages the flash drive functionality. I think that you could do something similar using USBDevice functionality. An external Flash/EEProm wouldn't be too difficult to add using the SPI libraries. Binary files are a pain to decode but *a lot* more space efficient (about 7x more efficient). It depends just how much data you plan on recording.

http://mbed.org/handbook/USBMSD

Thanks Giles, that looks like the stuff I need. I was looking at binary files exactly for that reason, currently I am just dumping everything from a CAN bus. Initially this was to a formatting txt file but it wasn't capturing all the data, I didn't do any testing but I assumed this was due to the time to write the txt file data to an SD card on the fly. No doubt when I get a chance to try this out I will be back with more questions :)