Lpc2000

Hello Eugene,

that might seem off topic but please try to increase the frequency to
the USB peripheral. 
There is a parameter in a SFR called VPBDIV and the default is set to
divide the CPU frequency by 4. Running at 48 MHz or 60 MHz this
results in 12 or 15 MHz clock for the USB perpheral which is connected
to the VPBBUS which is equivalent to the ARM APBBUS.

If not done so already please modify the VPBDIV to divide by 2 instead
of divide by 4. We have noticed some occasional problems going away
when we did this.

Hope this helps, Bob

--- In lpc2000@yahoogroups.com, "y3peng" <eugene.peng@...> wrote:
>
> Hello all,
> I am new to this group and to the LPC chips in general.
> I have been working on implementing an USB device using LPC2148. 
> 
> When the chip read in packets of data from the host PC, occasionally,
> a byte goes missing. I checked the data packets over an USB analyzer,
> and they appeared to be perfect. So the data got corrupted somewhere
> between acknowledging the data packet and reading the data from the
> USB endpoint RAM.
> 
> It might be of interest to you that I used a modified USB stack from
> the virtual com port example from phillip's website. The example was
> written for Keil, but it was ported to IAR workbench.
> 
> Sometimes the chip also hangs after writing a command to usb protocol
> engine, when it waits for CCEMTY to be set.
> 
> anyone seen this before?
> 
> Eugene
>