USB MSD example using NAND flash controller

[deuteron]

We are looking for any example of a USB device using the Mass Storage Device (MSD) class that uses the NAND Flash controller (NFC) to access a large flash memory, for example to make a USB flash drive. There are plenty of examples that implement the memory as RAM or using part of the on-chip flash. The tower TWR-K60F120M board seems to have all the necessary hardware, including a 2Gb NAND flash. Our problem is how to implement an MSD with a flash memory device whose block size is so big that we cannot allocate RAM to match that block size. We cannot add external RAM since the flexbus and the NFC share pins and are thus mutually exclusive. Do any examples exit, or has anyone manged to make a good-sized USB flash drive using a Kinetis Mcu? On the other hand, is anyone convinced that the lack of RAM makes this impossible? Any help would be appreciated.

[philipnye]

I don't have a full answer but I think you will find that you are wrong that you cannot add an external RAM. Although there is much pin sharing, the separate chip selects should ensure that the two do not conflict - whilst one is being accessed the other will be deselected and will just ignore the bus activity. Alternatively use a DRAM.