>>>>> "Caleb" == Caleb Kemere <ckemere@xxxxxxxxx> writes:
...
Uwe> Otherwise, how do you read on the PC side? Do yo do asynchronous
Uwe> reads like in libftdi-1.0/src/ftdi_stream.c?
Caleb> I did test the asynchronous mode, but now I think I've distilled
Caleb> the essence of the test down to the following really simple
Caleb> (blocking) code:
Caleb> int transferred = 0; int bytes = 0; while (bytes <
Caleb> MAXIMUM_TRANSFER) { last_result =
Caleb> libusb_bulk_transfer(ftdi.usb_dev, ftdi.out_ep, buffer,
Caleb> bufferSize, &transferred, 1000); if ((last_result > 0) |
Caleb> (transferred == 2)) break; else bytes+= transferred; }
Caleb> I've been messing around with different values for the
Caleb> read-chunksize of the FT2232H and the bufferSize of the bulk
Caleb> transfer. As a reminder, my data streams from the FPGA to the
Caleb> FT2232H at 6.5 MB/s. With that, I can consistently read for about
Caleb> a 30 s or so before I get a buffer overflow (at half speed, I can
Caleb> go for about 3 times that long). It seems like the USB subsystem
Caleb> should be able to handle that data rate for an arbitrary length
Caleb> of time, so I'm wondering what I could be doing wrong...
Caleb> thanks!
Two more things to consider.
- Run your program with valgrind to see if we have a memory leak.
- Try to read from the plain device /dev/ttyUSBx with ftdi_sio loaded
Otherwise, why do you stop when you read 2 bytes? The FTDI will alway return
2 status bytes, so this is a legal value which might happen sometimes.
Your program must also strip these two databyte from each transfer. Reading
from /dev/ttyUSBx strips these bytes automatic
Bye
--
Uwe Bonnes bon@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt
--------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------
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