I am trying to use a Vinculum VNC1L device to access USB Flash but am having some problems which look to me like the protocol is broken. Yes, I have contacted FTDI/Vinculum support but recent questions have gone unaswered (and unacknowledged). So I am asking here if anyone has experience of the device and its protocol?
The story so far.
- I have a board designed that has an NXP ARM, RAM, ROM, LCD and the Vinculum thingy.
- I have flashed the chip with the VDAP firmware version 3.66 and verified it.
- I'm currently big-banging the low level 'SPI' signals even though the CPU can do 'standard' SPI on these pins. This is to minimise the issues at this stage. The Vinculum SPI is an abuse of the term since the interface is only superficially like SPI.
- I can talk to the chip and have read/written data successfully, but unreliably.
My problem, though, is this. Most of the command protocol consists of sending commands and receiving status and data. Thats all well and good. However, when a USB device is plugged into or unplugged from either USB host port I get an asynchronous notification, by which I mean bytes are received via the interface without having sent a request. The problem a see with this is that there is a race condition where receive data is flushed just before sending a command then an asynchronous status measage is mixed up with then command response because it was generated between the flush and receipt of command. I can't see how its possible to get round this. My concern is when data is being written to a USB Flash device while a mouse/keyboard/printer or whatever is being connected on the other host port.
Has anyone seen this problem? Any pointer to resolving it?
Thanks in advance, Peter