[i2c] i2c-pport with kernel 2.6.X

pierre demanax baddemanax at hotmail.com
Fri Apr 20 19:00:31 CEST 2007


thanks for the fast answer .

Actually i measured with a common voltmeter 4,85 Volt on SDA and SCL . Even 
during the detection there are no variation of the voltage supply. ( 
unfortunatelly I have no scope to measure the signal)

I simply connect a PCF8574 to SDA and SCL and VCC and ground . I use my USB 
port to provide the power supply ( I hooked up the connector) ( I have a LED 
to show me that there is well power supply on the board).

There are no pull up resistor, as i measured almost 5V on SDA and SCL, i 
didn't think of adding a pull up. But I will give it a try.

The output of the PCF8574 are connected to power relay.

I also tried the sensors-detect function, but I got the same behaviour.


>From: Till Harbaum / Lists <lists at harbaum.org>
>To: i2c at lm-sensors.org
>CC: "pierre demanax" <baddemanax at hotmail.com>, khali at linux-fr.org
>Subject: Re: [i2c] i2c-pport with kernel 2.6.X
>Date: Fri, 20 Apr 2007 18:31:14 +0200
>Am Freitag 20 April 2007 schrieb pierre demanax:
> > Another strange behaviour, after inserting the i2c-pport.ko module, i
> > launched a i2cdetect 0, where it detects chips for all address even 
> > there was nothing connected on my parallel port.
>Does this still happen after you connect an pullup to the line you are 
>for sda? If the lines are floating you may very well always read "low" 
>means to the i2c layer that some chip seems to be acking everything. Thus
>it detects plenty of chips on the bus regardless what address it sends.
> > After the HW connection I could not communicate with the chip.
>How does you hardware setup exactly look like? Did you just connect an
>i2c client chip? Where did you get its power from? Did you connect pullups
>to sda and scl?

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