libftdi Archives

Subject: Re: Understanding the jtag/mpsse example

From: Uwe Bonnes <bon@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
To: libftdi@xxxxxxxxxxxxxxxxxxxxxxx
Date: Mon, 26 Jul 2010 12:20:58 +0200
>>>>> "Vaughan" == Vaughan Moss <vaughan@xxxxxxxxx> writes:

    Vaughan> --0003255762be49c31e048c473a34 Content-Type: text/plain;
    Vaughan> charset=ISO-8859-1

    Vaughan> Hi,

    Vaughan> I am experimenting using libftdi to implement jtag in our
    Vaughan> project to try and get away from using the expensive jtag tools
    Vaughan> each manufacturer wants to sell with their respective chips. We
    Vaughan> are hoping to place an ft2232h chip on our board and have one
    Vaughan> interface to do all the testing and/or programming.

Have a look at the xc3sprog SVN code at sourceforge. ioftdi.cpp implements
JTAG primitives for the use with different JTAG adapters. The read code is
not yet in the shape I like it to be , but it works for me and many
others. Async read of libftdi-1 would come handy, but as long as there is no
clean numbering scheme in libftdi, I fear to use is. Latest libftdi-0 read
handling ( Let ftdi_read_data() honor usb_read_timeout) should also help.

Feel free to reuse the code, give feedback when you fix something. Ask here
if you have problems that you can solve with googling, but I am away the
first two weeks of august.

If you have a FT2232(H preferred), forget about bitbang mode, more complex
and substantial slower.

    Vaughan> I have played around with bitbang mode finding all the examples
    Vaughan> i could and have now been trying to play with mpsse mode
    Vaughan> normally in c and using the python bindings, the area which i
    Vaughan> am confused by is the buffer being passed to the chip using
    Vaughan> ftdi_write_data.

    Vaughan> If anyone could explain what happens below or could point me in
    Vaughan> the correct direction I would greatly appreciate it.

Did you read the FT Datasheet and
Without an understanding of the MPSSE commands and the MPSSE structur, the
buffer values can't be understood.

    Vaughan> --0003255762be49c31e048c473a34 Content-Type: text/html;
    Vaughan> charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable

    Vaughan> <div>Hi,</div><div><br></div><div>I am experimenting using
Plaes, no html in mail.

Uwe Bonnes                bon@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Institut fuer Kernphysik  Schlossgartenstrasse 9  64289 Darmstadt
--------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------

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