Ok, Willy Robion's alternative USB timing is available with release 2.4p1
Use --altUSB (note the spellling) in the command line. That's
double-dash altUSB.
I see no difference, but perhaps others will note better or worse
results. Please give feedback.
Paul Alfille
On 6/7/06, Paul Alfille <[EMAIL PROTECTED]> wrote:
> As you noted, all the USB specific code is on module/owlib/src/c/ow_ds9490.c
>
> Look at function (line 257):
> static int DS9490_setup_adapter(const struct parsedname * pn) {
>
> Here is what Willy Robison suggested:
> I pourchased the weather station parts from AAG, and had
> a problem with everything under linux recgonizing all of
> the chips in the weather station. AAG indicated that
> the latest drivers from Dallas/Maxim addressed the problem.
> There was a terse reference to changing the slew rate
> to 1.37V/uS.
>
> Referrinhg to the DS2490 datasheet, the mode commands
> to set various parameters are listed. It seems that the default
> values for the 3 settings were not quite optimal...
>
> I've reworked the code fragment to match the style in
> ow_ds9490.c, but I don't have the calls to the routine in
> the correct locations at this point...
>
> I'll try to send some more information as I stumble on to
> a solution.
>
> To complicate things, I suspect that the timing requirements
> are dependant on the topology of the 1-wire bus , so a working
> solution may require that the parameters be set from the command
> line.
>
> --- xxx ---
> DS9490_BusParm( int slewrate,
> int low_time,
> int ds0_low,
> const struct parsedname * pn ) {
> int Value;
> int Index;
> int ret[3];
> /*
> * Slew Rate
> */
> Value = MOD_PULLDOWN_SLEWRATE;
> if(slewrate<0)
> Index = PARMSET_Slew1p37Vus;
> else
> Index = slewrate;
> if((ret[0] = usb_control_msg(pn->in->connin.usb.usb,
> 0x40, //
> RequestType
> MODE_CMD, // Request
> Value, // Value
> Index, // Index
> NULL, //
> 0, // Length
> TIMEOUT_USB )) < 0)
> LEVEL_DATA("DS9490_BusParm: Error MOD_PULLDOWN_SLEWRATE\n") ;
>
> /*
> * LowTime
> */
> Value = MOD_WRITE1_LOWTIME;
> if(low_time<0)
> Index = PARMSET_W1L_10us;
> else
> Index = low_time;
> if((ret[1] = usb_control_msg(pn->in->connin.usb.usb,
> 0x40, //
> RequestType
> MODE_CMD, // Request
> Value, // Value
> Index, // Index
> NULL, //
> 0, // Length
> TIMEOUT_USB )) < 0)
> LEVEL_DATA("DS9490_BusParm: Error MOD_WRITE1_LOWTIME\n") ;
>
> /*
> * DS0 Low
> */
> Value = MOD_DSOW0_TREC;
> if(ds0_low<0)
> Index = PARMSET_DS0_W0R_8us;
> else
> Index = ds0_low;
> if((ret[2] = usb_control_msg(pn->in->connin.usb.usb,
> 0x40, //
> RequestType
> MODE_CMD, // Request
> Value, // Value
> Index, // Index
> NULL, //
> 0, // Length
> TIMEOUT_USB )) < 0)
> LEVEL_DATA("DS9490_BusParm: Error MOD_DSOW0_TREC\n") ;
> if(ret[0]) return ret[0];
> if(ret[1]) return ret[1];
> if(ret[2]) return ret[2];
> return 0;
>
> }
>
>
> On 6/7/06, Michael Weber <[EMAIL PROTECTED]> wrote:
> > On Wed, 7 Jun 2006, Jan Kandziora wrote:
> >
> > > Am Mittwoch, 7. Juni 2006 21:44 schrieb Paul Alfille:
> > >> Actually, I have some alternative timing settings suggested by William
> > >> Robison that we could try.
> > >>
> > >> It's been hard to justify changing anything until we had test networks
> that
> > >> could be compared.
> > >>
> > >> I'll add it in, at least temporarily, add a command line flag, and
> package
> > >> it up.
> > >>
> > >> In the long run there are 3 cases:
> > >> 1. Old time best
> > >> 2. New timking best
> > >> 3. Varies by network.
> > >>
> > > Oh, there's actually another tweak Michael could try: Maxim supposes to
> add an
> > > RC circuit for medium length busses. Michael, see App. D of
> > >
> > > http://pdfserv.maxim-ic.com/en/an/AN148.pdf
> > >
> > > The whole document would be interesting to you, I think.
> > >
> > > Kind regards
> > >
> > > Jan
> >
> > Thanks for the suggestions.
> >
> > We are actually implementing the filter, but since the network is in a
> > slightly remote location (an observatory on Tenrife, where I only go to
> > fix problems) I was looking for a solution I could try remotely.
> >
> > The network is indeed a mixed topology, it consists of 2 Hubs, about 5-10m
> > apart from each other (and the master). We splitted it up (it was a bit
> > more complicated before) but that did not improve matters. Nor did using
> > USB instead of rs232.
> >
> > I will try the filter (I also take an oscilloscope to measure timings and
> > voltages) next week, but I would still like to play around with timings
> > (Maxim says something about 5us pulldown time for the 5Volts, which should
> > be tuned by the timing setting.
> >
> > Any suggestions to where I could insert some timing related changes in the
> > source code? Preferably changeable at runtime, but thats not really
> > important.
> >
> > Thanks again,
> >
> > Michael
> >
> >
> >
> > _______________________________________________
> > Owfs-developers mailing list
> > [email protected]
> >
> https://lists.sourceforge.net/lists/listinfo/owfs-developers
> >
>
>
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