I'm looking into adding support for USB Flash sticks to a current design, perhaps even for retrofit. The product volumes are in the small thousands a year. The product has an expansion connector that has power, a few GPIOs and a UART or SPI. Currently this connector is used to add a serial printer or a few other things. Now I'd like to add USB flash. Actually, no I wouldn't, but thats what I've been asked to add - one of the expansion devices is already an SD card interface but thats not what the customer wants...
The hardware is ARM7TDMI based with a few hundred Kbytes of spare flash for code/data. RAM is much tighter because the product is already developed. I might be able to squeeze 16K.
My first thought was the Vinculum VNC1L to take most of the design work away and because the SPI interface would allow it to bolt on. Has anyone here had experience of this chip that they would be willing to share (good or bad) ?
My second thought was to use a host controller chip on the bus (16-bit SRAM-like) which would would not allow retrofit but would give more flexibility and hopefully be cheaper and faster. The problem is developing the software - the thing is OS-less but knows about file system for SD cards (and SDHC). Anyone have experience of this approach with suggestions for a host controller chip and the difficulty of driving it?
Performance doesn't have to be great. The current SD Card incarnation can do file copy at ~70Kbyte/sec.
TIA Peter