libftdi Archives

Subject: thruput testing on FTDI245BM

From: "Steve DeLaney" <onramp123@xxxxxxxxx>
To: <libftdi@xxxxxxxxxxxxxxxxxxxxxxx>
Date: Sat, 14 Feb 2009 10:07:51 -0800
Thanks to help on this forum I was able to resolve this issue and get FTDI
up and running.  starting from examples/bitbang.c, I made a simple bulk
transfer
throughput test to measure the effect of baudrate and block size

the results executing on x86 show a dramatic difference.
starting with default block size of 64 bytes/9600 "baud" yieds around
250Kbit/second,
to 4096 block size/921600 baud yields over 4.5Mbit/sec

but now I'm starting to wonder about whats going on "under the hood"
so to speak.  for starters,

what is the effect of ftdi_set_baudrate()?  
is this like a classic serial port rate, or can an arbitrary clock rate 
be selected?  it seems to limit out at some point and return an error.

its hard to tell for sure whats going on in the chip since
there is no register level spec. bitbang.c includes a couple of steps
that seem optional:  "turning everything on", and "turning everything off", 
writing 0x0 and 0xff respectively to the bulk endpoint.  Is that just
required for bitbang?  because the thruput test works OK without it.

and what the heck is ftdi_enable_bitbang() doing?  writing to the control
endpoint?

Anyway will be happy to share the results of our testing as this
progresses...

/Steve



-----Original Message-----
From: Laurent Perez [mailto:laurent.perez@xxxxxxxxxx] 
Sent: Wednesday, February 11, 2009 11:41 PM
To: libftdi@xxxxxxxxxxxxxxxxxxxxxxx
Subject: Re: libftdi missing definition for usb_dev_handle

Hello Steve,

> now I am trying try track down usb.h (Erdfelt) containing a reference 
> to usb_dev_handle.  It does not appear in libusb-1.0.0, nor in 
> libftdi.  so it must be a system file?

libusb-1.0 is not backward compatible with the good old libusb-0.1.
In order to build and run programs that rely on libusb-0.1, you will need to
instal libusb-compat-0.1 compatibility layer [1]. You probably only miss
header file from this package. The lib itself should already be installed on
your system as much of usb relative tools hasn't been ported to new
libusb-1.0.

Regards ;


Laurent.



Links :
¯¯¯¯¯¯¯¯¯¯¯¯
[1] http://libusb.wiki.sourceforge.net/LibusbCompat0.1

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