Re: parport (i2c bus) maximum speed

["Petr Jakeš" <petr.jakes-VOAeGBCOg48@public.gmane.org>]

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>
> > Now we do SMBus communication through dme1737 (we have compatilbe chip on
> > the motherboard). I guess it is not possible to change the bus speed
> because
> > the master (DME1737) is generating the clock frequency of the SMBus.
>
> I don't think the DME1737 can act as an SMBus master, or can it? As far
> as I know the DME1737 is an SMBus slave and multiplexer, but not a
> master. If I am correct then what matters is the actual SMBus master on
> the motherboard.

Maybe I was not specific enough. Actually there is an SCH3114 chip on our
motherboard (http://www.smsc.com/main/catalog/sch311x.html ) and lm-sensors
need dme1737 module for this chip.
This chip acts as a SMBus master.

>
> > Just for your information we have PIC 16F887 connected to the bus as a
> slave
> > (which was really pain and a lot of SW hacking on the PIC side - it looks
> > like Microchip I2C HW/SW implementation does not work properly
> "sometimes").
> >
> > The good thing is we have slaves connected directly to the system SMBus
> and
> > we are doing MISSIVE communication on the bus (motors control, keyboard,
> LCD
> > display, I/O) and we have not observed any single problem (we are using
> > py-smbus binding for the communication).
> >
> > Are there some other ways (HW interfaces etc.) to get lm-sensors work on
> the
> > higher speed?
>
> I'm confused now. How is I2C/SMBus speed related to lm-sensors at all?


I am confused as well :-)
My feeling was lm-sensors are here to:

   1. enable SMBus/I2C communication (mainly using HW masters presented on
   the motherboards)  to communicate with SMBus slaves (mainly presented on the
   PC motherboards, ie clock, temperature, fans ....).
   2. enable SMBus/I2C communication with some other chips which one can
   connect to the bus

Because of above mentioned we have done some development and we are able,
using lm-sensors, to communicate with PIC microcontrolers (they are acting
as I2C slaves) on the VIA and Unicorn motherboards. From our test it looks
like we are communicating close to the 100kbps.

I was just wondering if it is possible to set the lm-sensors to communicate
faser, so I posted my question to this discussion group.


> Most SMBus controllers on PC motherboards run at low speeds (from 10 to
> 64 kbps), mainly because there's no need for speed when you only have a
> hardware monitoring chip and a couple SPD EEPROMs on the bus. So If you
> want high-speed you'll have to use an additional controller, but I
> don't know of any (except for parallel port or USB do-it-yourself
> adapters, but that's not much faster.)


OK, thanks for this info

Petr Jakes

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