[Linux-parport] Parport signals stability with SiS chipset

[Nate Jenkins]

Does "frobbing" help?  Maybe investigate "frob"  I am not sure if the lack
of this could do what you describe or not.  Or if it is chip specific...

Nate



----- Original Message ----- 
From: <tdlt at cecm.usp.br>
To: "Linux Parallel Port Development" <linux-parport at lists.infradead.org>
Sent: Tuesday, March 16, 2004 5:15 PM
Subject: Re: [Linux-parport] Parport signals stability with SiS chipset


> I have two computers with SiS chipsets and both of them have the
> same problem.
>
> When I try to send the data through the parallel port inside a
> while(1), the state of the pins is as I would like they to be,
> showing that the port sends the data, but not maintain the pins
> voltage.
>
> Under MS-Windows the stability of pins voltage is OK.
>
> I have problems printing large images using the parallel port in
> ECP or EPP mode, so I use this in SPP mode and I believe it is
> related to our problem with pins voltage...
>
> A workaround is to connect the port to a latch IC (i.e.
> 74373, 74374) and use one of the control pins as gates. I tried
> this and got good results (except that I cannot use one of the
> control pins). In your case it would work once you would make
> the program to control the jtag (at least is what I think).
>
> I don't know what is the problem with the SiS chipset and the
> Linux, but I tried this with kernel 2.2.21 and the problem is
> within it too, showing that the problem was not perceived or
> reported once before.
>
> I can help with the electronic solution (latch), but I don't
> know so much about Linux kernel source to help with the
> software...
>
> Thank you all.
>
> On Mon, Feb 09, 2004 at 11:24:49AM +0100, Eric BENARD / Free wrote:
> > Hi !
> >
> > I'm trying to get a small jtag software to run under Linux and I meet
problems
> > with the parallel port :
> > - on two PC (a Dell Intel based Notebook and an Asus VIA/AMD based),
> > everything is ok, I can write and read correct data to the board (an
ARM7
> > cpu)
> > - on the other PC (Asus Pundit with SiS651/962 chipset & Celeron4 CPU),
the
> > parport IO are always swinging so data gets corrupted.
> >
> > Both PC have the same settings (SPP). I tried with 2.4.23 & 2.6.1 &
2.6.2
> > kernels on the Asus without any success.
> >
> > I quickly tested on a SiS630 PC and I have the same problems than on the
> > Pundit, so this could come from a problem with the SiS chipset handling
> > parport.
> >
> > Of course, I checked that no other software was trying to use the
parport. I
> > unloaded lp, and only ppdev is loaded.
> >
> > The problem is the same if I try to access the parport directly (io @
0x378)
> > or through ppdev (/dev/parport0).
> >
> > Here is the schematic used for the JTAG adapter :
> > http://axl.freeyellow.com/iPAQ/xilinx-DLC5-pp2jtag.pdf
> >
> > Do you have an idea of what could be wrong ? Or maybe where I should
look to
> > get more details and solve this problem ?
> >
> > Many thanks for your help & best regards
> > Eric
> >
>
> -- 
> Thiago A. M. Delatorre
>
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