libftdi Archives

Subject: Re: ftdi_set_bitmode question

From: Chris Zeh <chris.w.zeh@xxxxxxxxx>
To: libftdi@xxxxxxxxxxxxxxxxxxxxxxx
Date: Tue, 26 Jul 2011 08:31:15 -0600
Hi Jo,

It is curious the difference between the two drivers, I'm hoping the
suggestions I sent you will help get everything going.

I'm looking at the schematics for the Morph, pg27 and it looks like
the pull-ups are on the FPGA side. (possibly this is a different
product than what you're
using?).(http://www.ftdichip.com/Support/Documents/DataSheets/Modules/DS_Morph-IC-II.pdf)

Going through the documentation it looks like this board is designed
to program the FPGA using the Passive Serial (PS) configuration, which
would be using the FTDI instead of the JTAG. Typically if you're using
the JTAG to program the FPGA you would tie the MSEL[0:1] lines to GND.
(See page 409 http://www.altera.com/literature/hb/cyc2/cyc2_cii5v1.pdf).
Although JTAG is a bully and can program the FPGA no matter what the
MSEL pins are set too. I believe tying these lines to GND will make
the FPGA insensitive to glitches on the NCONFIG line. Looking at the
board schematics this might not be possible.

Just some more details in case you're planning on laying out your own
board down the line...

Let us know how it goes.

Best regards,
Chris




On Tue, Jul 26, 2011 at 7:37 AM, Joachim Schambach
<jschamba@xxxxxxxxxxxxxxxxxx> wrote:
> From the schematics that FTDI provides it looks like there are no pullups or
> pulldowns on those lines, maybe the FPGA itself has some internal 
> pullups/downs.
> However, as you noticed, everything seems to work with the libftd2xx.
> The only reason I am working on this is that I noticed that the DEV_RST is set
> high, when I do nothing to the B port. So all I am trying to accomplish is
> setting this one line to 0. Any functionality that  can  do this would work 
> for
> me, I just thought BITBANG would be the easiest.
> Jo
>
> On 7/26/2011 4:28 AM, Uwe Bonnes wrote:
>>>>>>> "Joachim" == Joachim Schambach <jschamba@xxxxxxxxxxxxxxxxxx> writes:
>>     Joachim> Hi, I have a question about the usage of the ftdi_set_bitmode
>>     Joachim> function.  I am using a development board from FTDI called
>>     Joachim> MorphIC-II to evaluate the usage of the FT2232HQ chip. This
>> ...
>>     Joachim> I am trying to use BITBANG mode to port B to set the DEV_RST
>>     Joachim> line to 0, while leaving the other pins alone (by setting them
>>     Joachim> as inputs). I have been able to do this with the libftd2xx
>>
>> What are you trying to achieve? What other function should the FT2232H do,
>> either seqential or simultanious? Why can't you use MPSSE to set the PINs?
>>
>> Otherwise, are there appropriate pull-up/downs to keep the input lines from
>> floating? But as it works with ftd2xx, there should be.
>>
>> In the next weeks I don't have time to investigate further...
>>
>> Bye
>>
>
> --
> Dr Joachim Schambach                 tel: x1 512 471 1303
> The University of Texas at Austin    fax: x1 814 295 5111
> Department of Physics                email: jschamba@xxxxxxxxxxxxxxxxxx
> 1 University Station C1600
> Austin, Texas 78712-0264, USA
>
>
> --
> libftdi - see http://www.intra2net.com/en/developer/libftdi for details.
> To unsubscribe send a mail to libftdi+unsubscribe@xxxxxxxxxxxxxxxxxxxxxxx
>
>

--
libftdi - see http://www.intra2net.com/en/developer/libftdi for details.
To unsubscribe send a mail to libftdi+unsubscribe@xxxxxxxxxxxxxxxxxxxxxxx

Current Thread