Re: New approach to transfer exact data By FT2232H
- From: Paul Carpenter <paul@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Tue, 16 Jun 2009 14:14:55 +0100
In article <G8WdnV0-S-xy4arXnZ2dnUVZ_ridnZ2d@xxxxxxxxxxxx>,
hamsdeji@xxxxxxxxx says...
Hi all.
I really appreciate you guys to concern my past question.
(In the past thread, "For exact data transfer by using FT2232H." ,
I asked why the FT2232H makes data delay randomly WHILE I sent the
exact data from FPGA. like below:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9
0 1 2 3 4 5 3 4 5 6 7 8 9 0 1 2 3 4 5 6
7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6
7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6
..)
Now either data is being repeated or data is being missed, both of which
suggest driver or driver handling of transfers has timing issues.
Either insufficient buffering, incorrect buffer handling or too bloated
(in execution) to handle vagueries of your system.
Alternatively your system is choking.
I`ve tried to access with various ways.
Some told me that it is a problem of DEVICE DRIVER.
I also suspected its unstable device driver.
However,
I found the result which is received perfectly by SHUTING DOWN
my windows programs like Quatus, VC++, Explorer etc..
It success to transfer the 18MByte data without delay
but sometimes delay appears randomly in 1 or 2 points.
Still could be the driver, your application, or too low a spec
system.
So I think the communication between FT2232 and PC is interfered by
some window programs of PC.
Windows is NOT a real time operating system!
Two things to do while you are transferring correctly your data
a) Click and drag the window with your application about the screen
(this also works when playing movies on PCs as they become 'jerky'
due to missed frames/lines).
b) Put a known bad/scratched CD (or in some cases a blank CD-R) into
your CDROM/DVD drive.
Your application WILL fail to transfer correctly!
Another thing that can show this is to use explorer to browse all
computers on your network, with a clash between different systems
wanting to be browser master on a workgroup setup.
Actually, I made a PC application program with no protecting the app.
I wonder if it is real problem I have?
Is there some solution by modifying VC++ coding ?
IF YOU have any opinion about this, please tell me about that.
If you want to GUARANTEE a large data transfer you will need some form
of dedicated hardware (possibly larger buffer in your USB device) to
do the guaranteed capture of data.
Windows CANNOT guarantee a timed capture of high speed data, and gets
worse the larger the dataset size.
--
Paul Carpenter | paul@xxxxxxxxxxxxxxxxxxxxxxxxxxx
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