From mboxrd@z Thu Jan 1 00:00:00 1970 From: "=?UTF-8?Q?Petr_Jake=C5=A1?=" Subject: Re: parport (i2c bus) maximum speed Date: Fri, 13 Jun 2008 20:04:02 +0200 Message-ID: References: <20080613160205.60b719c3@hyperion.delvare> <20080613191707.13731136@hyperion.delvare> Reply-To: petr.jakes-VOAeGBCOg48@public.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============8266414946145940995==" Return-path: In-Reply-To: <20080613191707.13731136-ig7AzVSIIG7kN2dkZ6Wm7A@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: i2c-bounces-GZX6beZjE8VD60Wz+7aTrA@public.gmane.org Errors-To: i2c-bounces-GZX6beZjE8VD60Wz+7aTrA@public.gmane.org To: Jean Delvare Cc: i2c-GZX6beZjE8VD60Wz+7aTrA@public.gmane.org List-Id: linux-i2c@vger.kernel.org --===============8266414946145940995== Content-Type: multipart/alternative; boundary="----=_Part_28520_3048641.1213380242360" ------=_Part_28520_3048641.1213380242360 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Content-Disposition: inline > > > 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 ------=_Part_28520_3048641.1213380242360 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: 7bit Content-Disposition: inline
> 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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