Good morning.
(Half-offtopic question, since I don't use libftdi *yet*,
but I guess I will find the most FTDI knowledge in this
list.)
Short background info: I have to develop a circuit that
communicates with a Windows PC via USB. Datarates are fairly
high so I plan to use the FT2232H chip in sync fifo mode.
First tests have shown that it is possible to achive maximum
data rates of around 30MB/s writing (to device) and 40MB/s reading
(from device).
Now, that problem is that I observe data loss when reading
from the FTDI chip. For testing I designed a simple loopback
circuit into the FPGA that the FT2232H is connected to. The FPGA
reads data from the FT2232H and writes it back a few cycles later.
Reading the data into the PC (via calls to the ftd2xx.dll) I see
that sometimes single bytes are missing.
I connected a scope and a counter to the WRn and RDn lines of the
chip, timing relations are ok, and I see that the correct number
of read and write pulses are counted. However, the number of bytes
that I am able to read is less than the number of pulses.
FTDI has published errata for the FT2232H chip; the 'A' silicon
version according to this note had a problem:
<quote>This appears as though the data read from the FIFO has missed a byte.
...
This issue is corrected at silicon revision B.
</quote>
I use the FTDI minimodule, and the chip has silicon version B.
Now the questions:
Is it known that the FT2232H sync fifo mode still has this problem?
Could it be a driver (ftd2xx.dll) problem? Can it be that libftdi
works better?
Any tips?
Thanks,
Thomas
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